BBC Sky at Night 2013-05

TAKE YOUR ASTRO IMAGING TO THE NEXT LEVEL

Sky at Night THE BIGGEST NAME IN ASTRONOMY

WHAT’S HAPPENED TO

SOLAR

THE W BIGGES ORLD’S T & BES T N

Discover the cause of our star’s strange behaviour...

IGHT-SK GUIDE Y

MAXIMUM? PLUS

Build a solar filter for your scope

The perfect tool for observing detail on the Sun

Seeing through the Moon illusion

Why our satellite looks larger when it’s low

ALSO IN THIS ISSUE

An evening triple act Catch the close encounter of three planets Our special guide to the birth and death of stars

Noctilucent cloud season starts now! Could aurorae help us discover alien worlds? On test: Orion Optics carbon-fibre telescope

LETTER FROM THE EDITOR MAY 03

Welcome

This month’s contributors include...

At last, a belt of clouds you’ll be glad to see the sight of

LUCIE GREEN SKY AT NIGHT PRESENTER

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limate summaries show that in May the UK is blessed with more sunlight than any other month. With this – and the OLIVIA JOHNSON prediction that solar SCIENCE EDUCATOR maximum is expected Olivia explains why in 2013 – in mind, now is the best time to non-visible look out for the fascinating activity on the light is so surface of our own star. Dynamic displays of important sunspots and prominences await; if you don’t to astronomers as she have a solar scope, you’ll find our guide to talks us through the electromagnetic spectrum. how to adapt your regular telescope to safely observe the Sun on page 82. TOM MCEWAN To find out why we expect the Sun to be EXPERT OBSERVER more active this year, we asked solar physicist After 25 years of and The Sky at Night presenter Dr Lucie Green recording to tell us all about the predicted peak of the noctilucent 11-year solar activity cycle. Turn to page 32 for clouds, Tom her take on how this solar maximum fits into spills the insider secrets our understanding of our Sun’s behaviour. for observing this The Sun may play a role in the visibility of amazing phenomena. another phenomenon that can occur around CHRIS NORTH this time of year – noctilucent clouds. Rather SKY AT NIGHT REPORTER different to their cumulus, cirrus and stratus Chris’s role as outreach siblings at lower altitudes, these glowing veils officer for of tiny ice crystals form at the very edge of the Herschel our atmosphere and only become visible at Space night and at certain latitudes, when they’re lit Observatory puts him in an ideal position to tell us by the Sun after it has set below the horizon. about how stars are born. Read our guide to spotting them on page 74. Solar scientist Lucie explores the Sun’s strange behaviour as we approach a predicted solar maximum.

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One of the great things about noctilucent clouds is that they are relatively easy to image. If you want to take your astrophotography to the next level, you’ll find a fascinating feature on page 40, where we take you through eight key equipment upgrades and accessory choices you can make to really get the most out of those faint, far-travelled photons. Enjoy the issue!

Chris Bramley Editor

PS Next issue goes on sale 16 May.

Sky at Night LOTS OF WAYS TO ENJOY THE NIGHT SKY...

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In the magazine ON THE COVER 32

40

NEW TO ASTRONOMY? See The guide on page 80 and our online glossary at www.skyatnightmagazine.com/dictionary

32

WHAT’S HAPPENED TO SOLAR MAXIMUM?

62

STAR BIRTH

74

82 14 50 62 106

98

TRIED & TESTED

98

FEATURES

REGULARS

06 Eye on the sky

11 Bulletin

The latest astronomy and space news.

82 How to

32 What’s happened to solar maximum?

19 What’s on

Observe the Sun safely.

The latest stunning space images.

Astronomy events from around the UK.

Explore the mystery of our quiet star, get to grips with the solar cycle and learn how it affects sunspots.

20 Sky at Night diary

40 Take your astro imaging to the next level

22 Interactive

Become the next Astronomy Photographer of the Year.

62 The life of stars: star birth

How interstellar gas and dust becomes a ball of fire.

68 The life of stars: star death Why some stars explode rather than fading quietly.

74 The glow from the edge of space

Top tips for observing the only good type of cloud – the ethereal night-shining variety. skyatnightmagazine.com 2013

Your backstage pass to the TV show.

80 Skills 80 The guide The electromagnetic spectrum.

85 Sketching The Splinter Galaxy.

86 Scope doctor 87 Lost in space

Your letters, emails and tweets.

89 Reviews

26 SUBSCRIBE

Virtuoso auto-tracking scope.

Get your issues at a discount

28 Hotshots

The finest of your astro images.

47 THE SKY IN MAY Your 15-page guide to the night sky featuring our pick of the top sights, an all-sky chart, a deep-sky tour and much more…

First light 90 Sky-Watcher Heritage-90 94 Celestron AVX Go-To mount. Tried & tested 98 Orion Optics AG12 astrograph. 102 Books 104 Gear

106 What I really want to know is…

Can aurorae help us find exoplanets?

MAN IN SPACE iPAD APP

Celebrate 50 years of mankind’s adventure in space

The Man In Space app is more than a digital book – it’s a complete multimedia experience. Tap the screen to play videos, rotate spacecraft views and bring interactive elements into play. You’ll never feel closer to being in space. This app features:  3D views of legendary spacecraft, allowing you to examine them from different angles  Themed photo galleries featuring amazing images  Historic video footage  Interactive diagrams  360º panoramic views of the Moon  A foreword by Sir Patrick Moore

AVAILABLE NOW ON iTUNES – ONLY £3.99 To download visit www.skyatnightmagazine.com/man-in-space-ipad-app skyatnightmagazine.com 2012

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skyatnightmagazine.com 2012

The arid

planet MARS EXPRESS SPACECRAFT, 14 FEBRUARY 2013 With its deep depressions and sweeping arid planes, this composite image, taken by the High-Resolution Stereo Camera on ESA’s Mars Express spacecraft, reveals a great deal about the geological history of the Red Planet’s Amenthes Planum region. The image, which left to right spans a distance of 200km, shows evidence for water. At the bottom of the picture is a short, wide valley, its extinct tributaries fanning out from the central basin. This small channel eventually merges into the mouth of Tinto Vallis, a much larger river valley. Both would have emptied into Palos Crater, which lies just off the bottom right edge of this image. To the left edge of the shot is a 35-km wide crater surrounded by darker areas; these dark patches are the result of basaltic sand blown in by wind.

skyatnightmagazine.com 2012

ESA/DLR/FU BERLIN (G. NEUKUM)

Dessicated plains and dry riverbeds point to a long-gone wetter world

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 Pictor perfect HUBBLE SPACE TELESCOPE, 4 FEBRUARY 2013 The full extent of spiral galaxy ESO 121-6 in Pictor is revealed in this intricate image from the Hubble Space Telescope. From this angle – almost side-on – the galaxy’s spiral arms are hidden but its central bulge, packed tightly with young stars, glows with great intensity.

 Upper crust MARS RECONNAISSANCE ORBITER, 20 FEBRUARY 2013

ESA/HUBBLE & NASA , NASA/JPL/UNIVERSITY OF ARIZONA, ESO/VVV SURVEY/D. MINNITI. ACKNOWLEDGEMENT: IGNACIO TOLEDO, NASA/JPL-CALTECH/UCLA

The bizarre structures in this image from the Mars Reconnaissance Orbiter’s HiRise camera formed during ancient reactions between lava flows and subsurface water in the Amazonis Planitia. These are ‘rootless cones’, volcanic structures formed by lava flows rather than internal magma. Water would have found its way under the rapidly solidifying lava crust, causing ‘inflation’ – and leaving these raised edges.

Cosmic crustacean  EUROPEAN SOUTHERN OBSERVATORY 20 FEBRUARY 2013 This infrared image from the VISTA telescope in Chile reveals the landscape around the Lobster Nebula, a vast stellar nursery some 8,000 lightyears away in the constellation of Scorpius. Sitting alongside the gas clouds are dark tendrils of cosmic dust dappled with massive hot young stars.

skyatnightmagazine.com 2013

EYE ON THE SKY MAY 09

All hail the hunter WIDE-FIELD INFRARED SURVEY EXPLORER 5 FEBRUARY 2013 The Orion Nebula takes centre stage in an unusual hue in this ethereal image from NASA’s Wide-Field Infrared Survey Explorer. This startling representation of the nebula’s billowing clouds of cosmic dust covers a region nearly 100 lightyears across.

skyatnightmagazine.com 2013

BULLETIN MAY 11

Bulletin

PLUS

The latest astronomy and space news written by Hazel Muir

CUTTING EDGE

Our experts examine the hottest new astronomy research papers CHRIS LINTOTT LEWIS DARTNELL

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Comment

by Chris Lintott

The distance to the LMC was calculated by studying the light from eclipsing binary stars such as these

Galactic neighbour measures up

ESO/L. CALÇADA

The Milky Way’s next-door galaxy could clarify the Universe’s expansion THE DISTANCE TO one of our nearest galactic neighbours – the Large Magellanic Cloud (LMC) – has been measured with unprecedented accuracy. The new measurements suggest that the LMC lies 163,000 lightyears away. This result should help clarify the distances of other galaxies, which astronomers calculate by using nearby ‘standard candles’, objects of known brightness, to estimate the distances of objects farther away. The discovery will also help refine the expansion rate of the Universe. “This is a true milestone in modern astronomy,” says Rolf-Peter Kudritzki of the University of Hawaii at Manoa. “As we know the distance to our nearest neighbour galaxy so precisely, we can now determine the rate at which the Universe is expanding.” The LMC is a satellite galaxy of the Milky Way and is easily visible to the naked eye from the

southern hemisphere. It has a mass roughly 10 billion times that of our Sun. Using observations by telescopes in Chile, Kudritzki and his colleagues worked out the distance to the LMC by analysing close pairs of stars in the galaxy known as eclipsing binaries. By tracking changes in the brightness of the stars as they orbit and block each other’s light, the astronomers were able to calculate their intrinsic brightness and then, from their apparent brightness, estimate their distance. “The distance to the Large Magellanic Cloud represents a fundamental yardstick with which the whole Universe can be measured,” added fellow team member Fabio Bresolin, also from the University of Hawaii. > See Comment, right

The key to the accuracy of this remarkable new measurement is in the choice of stars. What is unique about this particular study is that the international team was able to concentrate on cool giant stars, simple specimens for which these local observations provide all the necessary information. They were also helped by the fact that it’s not just the stars that are simple; the Large Magellanic Cloud itself has a simple structure, and so the team was able to effectively account for the positions of the star systems that they were studying within the galaxy. It all adds up to a very careful calibration of the expansion rate of the Universe, albeit one that remains consistent with previous estimates based on the study of stars. At a time when new results from the Planck satellite conflict (slightly) with local measurements of the expansion rate of the Universe, such painstaking shoring-up of astronomy’s foundations is increasingly necessary. CHRIS LINTOTT presents The Sky at Night on BBC TV

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Black hole gets in a spin A supermassive black hole is rotating close to Einstein’s speed limit

News in brief HERSCHEL SPIES ROOTS OF JETS

NASA/JPL-CALTECH , ESA/NASA AND L. CALÇADA (ESO), ESO/C. MALIN, NASA/JPL-CALTECH/CORNELL/MSSS, ALMA (ESO/NRAO/NAOJ) J. VIEIRA ET AL, THINKSTOCK

ESA’s Herschel Space Observatory has recorded jets sprouting out from a black hole in unprecedented detail. Stéphane Corbel from Laboratoire AIM in France and colleagues studied an outburst of jets from the binary system GX 339-4, consisting of a sevensolar-mass black hole feeding on material from a companion star. The data allowed astronomers to probe the mysterious jets down to their bases. “It is the first time we could witness the onset of compact jets and follow their evolution,” says Corbel.

A supermassive black hole at the centre of galaxy NGC 1365 is the first to have its rate of spin accurately measured

FOR THE FIRST time, astronomers have precisely measured the spin rate of a supermassive black hole. Two X-ray space observatories have shown that the black hole’s gravity is whirling space around at astonishing speed – almost the speed of light. “This is the first time anyone has accurately measured the spin of a supermassive black hole,” says team leader Guido Risaliti from the HarvardSmithsonian Center for Astrophysics in Cambridge, Massachusetts. The black hole, which is about two million times as massive as the Sun, sits in the centre of a galaxy called NGC 1365, which lies around 56 million lightyears from Earth. Matter falling towards the black hole forms a hot swirling disc – an ‘accretion disc’ – that emits bright X-rays. Einstein’s theory of gravity predicts that the faster a black hole spins, the closer the accretion disc lies to the black hole. By measuring these X-rays using NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and ESA’s XMMNewton spacecraft, Risaliti and his colleagues measured the position of the accretion disc’s inner edge. “We can trace matter as it swirls into a black skyatnightmagazine.com 2013

hole using X-rays emitted from regions very close,” says NuSTAR scientist Fiona Harrison from the California Institute of Technology in Pasadena. The measurements thus allowed the astronomers to calculate the black hole’s spin rate. “This is hugely important to the field of black hole science,” says Lou Kaluzienski, a NuSTAR scientist from NASA headquarters. Although astronomers have estimated black hole spin rates before, earlier measurements were uncertain because intervening gas clouds could have obscured the black holes and confused the results. But astronomers are confident of the new spin measurement because NuSTAR, launched in June 2012, could detect a very broad range of X-ray energies penetrating out from much deeper into the black hole’s environment. This new result could clarify how supermassive black holes grow. It’s likely the fast-spinning hole grew monstrous due to continuous feeding that spun up its momentum – rather than small ‘snacks’ of gas that would make it rotate more slowly. www.nustar.caltech.edu

SKYLAB’S 40TH ANNIVERSARY

On 14 May 1973 NASA launched Skylab, the US’s first manned space station, into orbit from Kennedy Space Center, paving the way for the human habitation of space. This revolutionary space station orbited Earth for six years and hosted three manned missions. Although small, Skylab was packed with the latest technology of the day, including a multi-spectral solar observatory that scientists eventually used to identify coronal holes on the Sun for the first time.

BULLETIN MAY 13

GIANT PLANETS TAKE THEIR TIME TO MATURE News in brief A PLANET 130 lightyears from Earth has shed new light on planetary formation. Studies of the planet’s chemistry suggest it formed by ‘core accretion’, a process in which an atmosphere gradually accumulates around a planetary core. The planet, HR 8799c, is seven times as massive as Jupiter. Quinn Konopacky from the University of Toronto and colleagues analysed observations of it by the Keck Observatory in Hawaii. “By studying HR 8799c, we get a peek at how Jupiter-like planets look shortly after they form,” says Konopacky. They found the planet has a higher carbon-tooxygen ratio than the host star, suggesting it formed gradually as water ice condensed in the planetary disc, leading to an atmosphere depleted in oxygen. The alternative hypothesis – that it formed through sudden collapse of a gas cloud – seems unlikely. http://keckobservatory.org

HOPE FOR ANCIENT LIFE ON MARS

Giant planet HR 8799c is thought to have formed slowly

ALMA celebrates completion in Chile

NASA’s Curiosity rover has discovered evidence that Mars could have supported microbial life long ago when the planet’s climate was warm. The rover drilled into rock near an ancient stream bed and showed it contains sulphur, nitrogen, hydrogen, oxygen, phosphorus and carbon – key chemical ingredients for life. “A fundamental question for this mission is whether Mars could have supported a habitable environment,” says Michael Meyer from NASA’s headquarters in Washington DC. “From what we know now, the answer is ‘yes’.”

The vast observatory’s antennas are now gearing up for action ALMA is the world’s largest radio telescope and will be fully operational by the end of the year

IN MARCH, AN official ceremony marked the completion of the Atacama Large Millimeter/ submillimeter Array (ALMA), a vast network of 66 dish antennas in Chile’s Atacama Desert. ALMA should reveal more details about star birth and infant galaxies in the early Universe. The project is a collaboration between Europe, north America and east Asia, in cooperation with Chile. “Thanks to the efforts and countless hours of work by scientists and technicians in the ALMA community around the world, ALMA has already shown that it’s the most advanced millimetre/

submillimetre telescope in existence, dwarfing anything else we had before,” says project director Thijs de Graauw. “We are eager for astronomers to exploit the full power of this amazing tool.” The array has 54 12m-wide dishes and 12 smaller 7m-wide dish antennas, which can be arranged in different configurations with a maximum antenna spacing of 16km. Astronomers hope it will give new insights into how planets form around distant stars and also measure the distribution of molecules – many of them essential for life – that form in interstellar space. www.almaobservatory.org

STARS BURST INTO LIFE EARLY

The most intense bursts of star birth began in the Universe 12 billion years ago, a billion years earlier than previously thought. An international team made the discovery using ALMA (see left). The team studied bursts of star birth in extremely young massive galaxies. “Our next step is to study these objects in greater detail and figure out exactly how and why they were forming stars at such prodigious rates,” says team member Daniel Marrone from the University of Arizona.

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CUTTING EDGE

Our experts examine the hottest new research

Seeing through the Moon illusion The science behind this familiar apparition may finally have been explained WORDS: CHRIS LINTOTT The mystery of why the Moon looks bigger at the horizon has baffled experts since antiquity

real world. The Ebbinghaus effect also fails to explain why the illusion isn’t seen when we look at a photo. Instead, this paper argues that the Moon illusion is caused by a problem with depth perception. We use our two eyes to make judgments about how far away something is – especially, in this case, the sky. If both eyes show exactly the same image, we assume the object they’re trained on is far away. Crucially, however, our

WILL GATER

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ave you ever noticed that the Moon looks larger when it is lower in the sky? The effect can be quite striking, especially at or around the time of full Moon. The Sky at Night has a long history with this ‘Moon illusion’, as one of the early systematic attempts to study it was filmed for a programme in the 1960s. Now evidence from a new paper calls that study into question. There’s no argument that the Moon illusion is a trick of the eye – the Moon, after all, appears the same size in photographs wherever it is in the sky. The question is why the brain behaves quite so strangely. That early experiment on Selsey Beach, and others like it, suggested the cause was due to a confusion about the way the brain interprets size. The experiments suggest that the brain takes its cue from neighbouring objects, leading to an apparent difference in the size of the Moon when it is high up in the sky, and when it is low down and can be easily compared to buildings, trees and so on. This relates to the Ebbinghaus effect, a well-known optical illusion named after German psychologist Hermann Ebbinghaus, in which circles appear to be different sizes when they appear near to other circles. This new paper, by two researchers at Susquehanna University in Pennsylvania, puts forward a different theory. They’re motivated by the fact that the Ebbinghaus effect never increases the perceived size of a circle by more than 10 per cent, whereas many observers report an apparent doubling in the size of the Moon. Previous attempts to measure the size of the Moon illusion conducted inside planetaria do not, it seems, adequately reflect its strength out in the skyatnightmagazine.com 2013

“We assume the sky is infinitely distant, with the Moon in front of it. This causes a confusing contradiction”

Chris Lintott is an astrophysicist and co-presenter of The Sky at Night on BBC TV. He is also the director of the Zooniverse project

brains assume the sky is infinitely distant, with the Moon in front of it. This causes a confusing contradiction. So when the Moon is low down with a skyline to help us judge distances, both Moon and sky appear close, and the Moon appears bigger; when it is high up, both appear further away. The illusion is still there then, when the Moon is high up, but there are so few clues to help us estimate distances to the sky that its effect is significantly lessened. So is that the mystery solved? Not quite. To prove their point, the team are planning to create artificial images that have been arranged to induce the illusion and they also want to measure people’s perceptions of how far away the sky is. For my part, I’m intrigued by a note in the paper, otherwise unremarked, which claims that the Moon illusion disappears if you stand on your head.

CHRIS LINTOTT was reading… Binocular disparity as an explanation for the Moon illusion by Joseph Antonides and Toshiro Kubota. Read it online at http://arxiv.org/abs/1301.2715

BULLETIN MAY 15

News in brief

Did comets seed life on Earth? The dusty snowballs could have delivered life’s building blocks

In March, scientists released the most detailed ever map of the cosmic microwave background (CMB), the afterglow of the Big Bang. It was compiled using data from ESA’s Planck satellite. The CMB is light that began to flood through the cosmos when it was just 380,000 years old. Scientists say the new map contains some peculiar features that are still to be satisfactorily explained. “The extraordinary quality of Planck’s portrait of the infant Universe allows us to peel back its layers to the very foundations, revealing that our blueprint of the cosmos is far from complete,” says JeanJacques Dordain, ESA’s director general.

ESA AND THE PLANCK COLLABORATION, ESA, THINKSTOCK X 2, ESO/M. KORNMESSER

HERSCHEL ENDS ITS MISSION

ESA’s Herschel Space Observatory’s mission has ended because the spacecraft has exhausted its supply of helium coolant. The spacecraft, launched in 2009, required extremely cool instruments to make sensitive far-infrared observations of objects such as distant galaxies and newborn planetary systems.

Simulated comet conditions in an ultra-cooled vacuum proved amenable to the creation of complex dipeptides

may well have had an extraterrestrial origin,” says Richard Mathies, a chemist at the University of California at Berkeley who is co-author of the paper published in The Astrophysical Journal. www.berkeley.edu

DISTANT STARS WERE MILKY WAY’S LUNCH

The Milky Way once devoured an entire galaxy

Looking back

PLANCK MAPS THE ANCIENT COSMOS

SIMULATIONS OF ICY snowballs in space have revealed evidence that comets crashing into Earth could have jump-started life on our planet. Scientists had already discovered basic organic molecules like amino acids in meteorites. Now cold vacuum experiments have shown that in the space environment, amino acids can link into pairs – dipeptides – that could have been delivered to Earth on comets. They may then have seeded the growth of the complex proteins and sugars needed for life. “It’s fascinating to consider that the most basic biochemical building blocks that led to life on Earth

NASA’S HUBBLE SPACE Telescope has revealed the remains of a galaxy that was ‘cannibalised’ by the Milky Way. Its stars form a shell around our Galaxy’s outskirts. Astronomers made the discovery using Hubble observations to measure the motions and densities of distant stars, which suggested they are the remains of a galaxy ripped apart by our Galaxy’s gravity billions of years ago. “Hubble’s unique capabilities allow astronomers to uncover clues to the Galaxy’s remote past,” says team member Roeland van der Marel from the Space Telescope Science Institute in Maryland. www.hubblesite.org

The Sky at Night May 1988 On 8 May 1988, the guest on The Sky at Night was Halton Arp, an American astronomer who was then working in Germany. Arp discussed his views on quasars – extremely energetic galaxies – that vigorously challenged the prevailing consensus. Quasars were first discovered in the late 1950s, and most

astronomers were convinced that they lay at vast distances, receding at enormous speeds due to the expansion of the Universe. Arp begged to differ. In his own work on galaxies, he became convinced that the huge distance estimates for quasars were a mirage. Arp argued that many pairs of quasars reckoned to be

lieves Halton Arp be nearer be ay quasars m e think w an th rth Ea to extremely distant were actually physically connected to galaxies that are much closer to Earth. Although he’s in a tiny minority, Arp maintains to this day that the distances to quasars – and many other cosmological ideas like the Big Bang theory – are fundamentally flawed.

skyatnightmagazine.com 2013

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CUTTING EDGE

Our experts examine the hottest new research

Predictions from the past A study of old aurora records has helped develop predictions about future solar activity WORDS: LEWIS DARTNELL Visual records of aurorae offer a longer-term view of solar activity than the telescopic sunspot record

closely to the periods of the ‘wobbles’ in the Sun’s position caused by the orbiting masses of Jupiter, Saturn, Uranus and Neptune. But the power in this modelling comes not from simply trying to fit an equation to data already in existence, but extending the purported patterns into the future – to predict. The Hungarian aurora record only extends up to 1960 (when naked-eye observation

THINKSTOCK

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he Sun is a very dynamic, ever-changing object. Solar activity – in terms of the strength of the solar wind and the number of sunspots, flares and coronal mass ejections – varies greatly over time. This solar activity and the ‘space weather’ it drives has important effects for life on Earth, especially now our civilisation is so reliant on electrical distribution grids. Scientists trying to study the Sun, and better understand space weather and its influence on the Earth are faced with a problem. Solar activity varies in a rhythm and not every one of these cycles is equivalent. Direct measurements of solar activity – such as counting sunspots – only date back to around the time of the invention of the telescope (see ‘What has happened to solar maximum?’ on page 32). To help understand the long-term variations in the Sun’s activity we need observations that go as far back in time as possible. In this new paper, Nicola Scafetta and Richard Willson present exactly that. Scafetta and Willson have worked with the historical record of naked eye sightings of auroral activity over Hungary from 1523. These Northern Lights are caused by material streaming from the Sun that is deflected by our planet’s magnetic field to strike the atmosphere around the poles. Because Hungary is fairly far south, aurora seen there relate to only the most intense outbursts, when the Sun is most active. Using a mathematical technique known as harmonic analysis to search complex variations for rhythmical patterns, the researchers found several longer-term cycles in this proxy of solar activity, with periods of roughly 43, 57, 86 and 171 years. These correspond skyatnightmagazine.com 2013

“What about forecasting? Scafetta and Willson’s model predicts a prolonged solar minimum around the 2030s”

Lewis Dartnell is an astrobiologist at University College London and the author of Life in the Universe: A Beginner’s Guide

was abandoned in favour of photography) and so Scafetta and Willson ran their model forwards from this point to see if their modelled oscillations continued to successfully match reality. Their model predicts a particularly low solar minimum in the early 1970s and a significant maximum over the years 2000-2002, which was indeed what instruments saw. This validates the model and gives us confidence that it faithfully tracks actual solar behaviour. So what about forecasting far into the future? Well, Scafetta and Willson’s model predicts a prolonged solar minimum around the 2030s, as is also predicted by other similar models. The important conclusion here is that the solar activity cycle is driven not just by internal dynamics deep within the Sun, but also by the gravitational influences of the larger planets in the Solar System.

LEWIS DARTNELL was reading… Planetary harmonics in the historical Hungarian aurora record (1523-1960) by Nicola Scafetta and Richard C Willson. Read it online at http://dx.doi.org/10.1016/j.pss.2013.01.005

WHAT’S ON MAY 19

What’s on

Our pick of the best events from around the UK

The International Astronomy Show Warwickshire Exhibition Centre, Leamington Spa, 17-18 May

Live Skies Life Science Centre, Newcastle upon Tyne, 4-31 May, 4pm Every weekend throughout May, the Life Science Centre’s on-site planetarium will be entertaining visitors with the Live Skies show, each 30-minute demonstration showcasing what’s visible in the sky that particular night. With images direct from the nearby Kielder Observatory, here’s where to find rural dark skies right in the heart of Newcastle. www.life.org.uk

AstroCamp Brecon Beacons, 3-6 May Following the success of the first AstroCamp in September 2012, preparations are underway for the return of this popular star party. Held within the Brecon Beacons mountain range in Wales, an area recently designated an International Dark Sky Reserve, this year’s event is set to be bigger and better than the first, with more telescopes, talks, quizzes and a country pub just around the corner. www.astrocamp.org.uk

PICTHKE

OF MONTH A major new astronomy show makes its debut in the Midlands this month

LIFE SCIENCE CENTRE, NASA/JPL/SPACE SCIENCE INSTITUTE, THINKSTOCK X 2

One of the year’s most highly anticipated astronomy events will take place in the heart of Warwickshire this month. Organised by UK Astronomers Ltd, the International Astronomy Show – which is in its inaugural year – is set to be the biggest event of its kind outside London, with over 40 astronomy dealers and specialists in attendance. As well as a chance to check out all the latest astronomy kit, there will be the opportunity to attend a range of

fascinating talks from some of the country’s most esteemed astronomers, astrophotographers and physicists. The venue has 2,000 free car parking spaces, so parking shouldn’t be a problem, and a large on-site restaurant will provide refreshments. Tickets start at £7 a day, but keep an eye on the show’s website for special offers on ticket prices, as well as news of any additions to the bill. www.international-astronomy-show.com

BEHIND THE SCENES

Missions to asteroids East Ayton Village Hall, Scarborough, North Yorkshire, 17 May, 7.30pm Scarborough and Ryedale Astronomical Society welcomes Dr Simon F Green from The Open University, who will be discussing the latest developments in asteroid research. Discover some of the amazing spacecraft that have already visited these ancient space rocks and learn more about future missions. Tickets cost £2 for non-members. www.scarborough-ryedale-as.org.uk

THE SKY AT NIGHT IN MAY and

One, 5 May, around midnight (repeated Two, 11 May, midday)*

Saturn’s rings will be tilted open during opposition

Four, 6 May 8pm;

STUNNING SATURN With the Ringed Planet in our evening skies, Lucie Green and Chris Lintott investigate Saturn’s atmosphere. Pete Lawrence and Paul Abel illustrate Saturn’s opposition effect, and Chris North previews the new camera soon to be fitted to the Internation Space Station. *Check www.radiotimes.com as times may vary

MORE LISTINGS ONLINE Visit our website at www. skyatnightmagazine.com/ whats-on for the full list of this month’s events from around the country. To ensure that your talks, observing evenings and star parties are included, please submit your event by filling in the submission form at the bottom of the page.

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diary The Sky at Night team learn all about meteorites and get some great views of Saturn, but miss seeing Comet C/2011 L4 PANSTARRS, writes Paul Abel

BBC, PAUL ABEL X 4

M

eteorites! These chunks of space rock are large enough to have survived entry through our atmosphere and made it down to the ground, thus ending – often in dramatic style, like the recent Russian meteorite – what may have been a journey of many thousands of years. As they are asteroids or pieces chipped off the neighbouring planets and the Moon by collisions with asteroids, they can tell us a great deal about conditions in the early Solar System, and we were lucky enough to film meteorites and their stories for April’s Sky at Night. For this episode the team split up and travelled to different locations. Chris Lintott and Lucie set off to the Natural History Museum, while Jon, Pete, Chris North and myself were to be based in Wiltshire. Chris interviewed Natural History Museum curator Dr Caroline Smith, who showed him the impressive collection of meteorites the museum has obtained over the years. I’m quite envious that Chris got to hold the Tissint meteorite – an ancient piece of Mars which has provided yet more evidence that there was once running water on the planet. To be honest, it was probably for the best since it would only be a matter of time before I dropped the thing and made this rare artifact even rarer! Also at the Natural History Museum, Lucie interviewed Anton Kearsley, who found what looked like a plain, boring skyatnightmagazine.com 2013

rock in the wilds of Australia. However, investigation of this unassuming rock with an electron microscope unlocked its geological secrets and revealed a fascinating story – it turned out to be a fragment from the Sea of Tranquility on the Moon, an incredibly rare find.

Jane Fletcher does a sound and camera test

Any old iron? There was one more interview to be done for this episode, with Prof Colin Pillinger. He told Jon the tale of the Danebury meteorite, a space rock unearthed during an archaeological dig at the Iron Age hill fort of Danebury in east Hampshire. Colin wanted to see if this meteorite was part of the Lake House meteorite, which had spent many years outside the front door of a stately home in Wiltshire. Alas, the Danebury meteorite turned out to be only a few thousand years old, whereas the Lake House meteorite seemed to be in the order of 32,000 years old. It may well be the oldest meteorite in England. Filming for the rest of us took place on 14 March. There was much to do – Pete and myself were to record a beginners’ guide to observing Saturn to coincide with

Production coordinator Ali Suker discusses the filming sch edule with Peta and Steve Bos ley

its opposition at the end of April. Jon and Chris North, meanwhile, recorded Space Surgery, a new feature in which they answer viewers’ questions on subjects ranging from observing to cosmology. There was one other thing

>

BEHIND THE SCENES MAY 21

Jon looks at the Moon through a Wiltshire AS member’s telescope

we were all hoping for: a glimpse of Comet C/2011 L4 PANSTARRS. While we were filming, the icy wanderer was a naked-eye object and visible in the evening sky: not overly bright but binoculars would show it nicely. We needed a clear night! The location of the shoot was at Barbury Castle, a Wiltshire hill fort with wide views of the surrounding downs and dark skies. When I arrived, the weather didn’t look too promising: the clouds were quite thick and the forecast predicted wintery showers. But the members of Wiltshire Astronomical Society who had joined us weren’t dismayed – one, Pete Glastonbury, had brought his family and remained optimistic that we would see something, as did Jon – which I always find incredible given how many Sky at Night location shoots he’s been on! Then a remarkable thing happened: the clouds started to break up and the skies cleared. As this happened, the temperature plummeted and it became perishingly cold. Two of the beginners

semi-translucent C Ring. Pete Lawrence and I pointed out the best way to see these features with a small scope and the features to look for. Also joining us from January’s programme were Peta and Steve Bosley. They had brought their Go-To telescope with them and were hoping to get a view of the comet too. In classic Sky at Night fashion, Peta and Steve helped me to demonstrate what is meant by opposition. Simply put, opposition occurs when an outer planet, the Earth and the Sun lie in a straight line with Earth between the two. As a consequence, the planet is due south at midnight and is

“The clouds started to break up and the skies cleared. As this happened, the temperature plummeted” we had invited on previous episodes also joined us – Christina Chester and Derek Agar. Both had been persevering with their telescopes since we saw them last on January’s programme.

VICTOR DE SCHWANBERG/SCIENCE PHOTO LIBRARY

Spying Saturn Although Saturn is every bit as dynamic as Jupiter, its colourful cloud bands and zones are hidden by a layer of petrochemical smog. In spite of this apparent ‘quietness’, Saturn is not beyond throwing the occasional surprise storm, so it’s well worth keeping an eye on. The planet’s rings, which are now wide open, show a multitude of details including the Cassini Division and the darker,

observable for much of the night. Pete and I reminded viewers to look out for the opposition effect (also known as the Seeliger effect) on Saturn. This is when Saturn’s rings brighten appreciably for a few hours around opposition. Afterward, they return to normal. I have seen the effect a few times: it can be very pronounced and with the rings wide open this is a good time to look. As darkness fell, the wind picked up to chill us all further. The brighter stars were now shining brightly and the transparency was good. Except of course, around C/2011 L4 PANSTARRS. Alas, the cloud could not be banished completely and the area of the sky that contained the comet remained stubbornly covered. As Jon and Chris

Jon attempts to observe from higher gr ound, while Ali records pr oduction note s

recorded Space Surgery, Pete and I were able to use the telescopes that the Wiltshire folks had brought to get some lovely views of the Moon and Jupiter. We didn’t get to see the comet in the end, but it was great to see our beginners again and meet the good people of Wiltshire Astronomical Society. Barbury Castle was an interesting place to shoot, but by now the wind whistled around the dark, bleak countryside. I have to confess, I have never been so delighted to see a car, nor found the sound of its heater so welcome! S

THE SKY AT NIGHT IN MAY One, 5 May, around midnight (repeated Four, 6 May 8pm; and Two, 11 May, midday)*

STUNNING SATURN Lucie Green and Chris Lintott examine a storm in Saturn’s atmosphere. Pete Lawrence and Paul Abel illustrate the planet’s opposition effect, and Chris North previews a new camera for the International Space Station. *Check www.radiotimes.com as times may vary

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22

Interactive EMAILS • LETTERS • TWEETS • CROSSWORD

This month’s Email us at [email protected] top prize: four Philip’s books The ‘Message of the Month’ writer will receive four top titles courtesy of astronomy publisher Philip’s. Heather Couper and Nigel Henbest’s Stargazing 2013 is a month-by-month guide to the year and you’ll be able to find all the best sights with Patrick Moore’s Guide to the Night Sky. Stargazing with Binoculars by Robin Scagell and David Frydman contains equipment and observing guides, and you’ll be viewing planets, galaxies and more with Storm Dunlop’s Practical Astronomy.

MESSAGE OF THE MONTH A happy tale with a happier ending

I thoroughly enjoyed reading the tributes to Sir Patrick Moore from his colleagues in the February edition of Sky at Night Magazine (page 13). One story Pete Lawrence shared was when he and Patrick decided to write a book together, and how Patrick had his part typed up just a few days later. This inspired me to buy the book and it helped me to solve a problem I have had for a couple of months now: how to stitch separate pictures of the Moon together taken at the prime focus of a telescope. The book recommended Microsoft Image Composite Editor (ICE) and after 10 minutes using this software I had my first ever Moon mosaic! So I thank Pete and Patrick, as they helped me to create my first ever Moon image. I used 1/160-second exposures at ISO 1600, taken through a Canon EOS 550D attached to a Sky-Watcher 130P EQ2.

Adam’s combined Moon montage

Adam Delmage, via email

A very atmospheric image of the waxing crescent, Adam. Microsoft Image Composite Editor (ICE) is a very useful program – readers may be interested to know that it is free to download too. See http://bit.ly/ICE_mosaic to read more from Microsoft about this image-stitching software. – Ed

Early encounters run deep

Þ Right to left: Patrick with

Lawrence and friend at Widey School, circa 1963

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Patrick Moore’s passing was a deeply sad and significant occasion for many. For me it brought to mind the occasion when I first met him, back in 1963. I was a teenager facing O-levels at Widey Technical School in Plymouth. I had developed an interest in astronomy and wanted to make it my career. There was no local advice available so I wrote to Patrick Moore to ask him how I should start. He replied in a very helpful manner and added that he would be visiting Plymouth soon and would be happy to pop in to see me. I vividly remember opening the front door to

him with a feeling of utter awe. Together with two friends, we spent a wonderful hour or more chatting and then we went to my school where I had helped set up an observatory with a 10-inch telescope. I went on to study physics at the local College of Advanced Technology, helped to form the Plymouth Astronomical Society with friends, and in 1968 I started work at the Radio and Space Research Station, achieving my wish to become a professional astronomer. I’ve since worked on the UK-5 and UK-6 astronomy satellite projects and was closely involved with the Infrared Astronomical Satellite (IRAS) project that produced the first infrared map of the Universe. Patrick’s advice and genuine interest have remained with me throughout. Lawrence Harris, Stowupland, Suffolk

As a formative experience, they don’t get much more positive than that. Thank you, Lawrence. – Ed

LETTERS MAY 23

Gone with the wind

The big debate Have your say at http://twitter.com/ skyatnightmag @skyatnightmag asked: Have you been lucky enough to spot Comet C/2011 L4 PANSTARRS this month? @sjb_astro A poem (apologies to Pvt S Baldrick): Cloud cloud cloud cloud; cloud cloud cloud; cloud cloud cloud cloud; cloud cloud cloud. ‫@‏‬PhilipJennings1 YES! Despite sky mostly clouded. Couldn’t see it naked eye, but lovely little comet in binos. Started snowing just as it set! ‫@‏‬SpireWeather After five days’ searching in vain, I got a photo from Salisbury on Sun 17th March. @samuelpeepses I live in London, England. We all know that if there’s a once in lifetime astronomical event, it WILL be cloudy. @laurashell2 Lucky enough to see it at Griffiths Observatory tracking down into the horizon. @jonwarrener Quite the opposite. Not had one chance to see it at all yet. Still hopeful though.

In Lucie Green’s article on the solar wind in February’s edition of Sky at Night Magazine (page 67), she explains that a million tonnes of charged particles are emitted by the Sun every second and that it radiates out into space until it reaches the interstellar medium. What happens to the particles when they get there and what form do they ultimately take? The Sun’s age – 4.5 billion years – suggests that it has lost a staggering amount of material in that time. David Tart, via email

The charged particles that flow out from the Sun in the solar wind keep going until they are stopped by the pressure of the gas between the stars – the interstellar medium. These particles are so spread out that they don’t collide with each other and don’t change at all. While the Sun does lose a million tonnes of mass a second in the solar wind, its mass is a billion billion billion tonnes, so it won’t run out of material for another million billion years! Of course, this is ignoring mass changes due to nuclear fusion and any comets that might fall into the Sun. – Lucie Green

Look on the Wight side As you can see from these photos, fog and cloud hampered any chances of serious astronomy at this year’s Isle of Wight Star Party from 7 March, organised by the Vectis Astronomical Society. Nevertheless, the event was an excellent opportunity to catch up with old friends, which more than made up for the lack of stars.

READERS’ SCOPES This is my 16-inch Orion Dobsonian with my astro friend Anna Sanders from Guildford. The telescope has an 3mm-thick carbon tube, which I had made as a one-off by my friend Richard Manby. The mount has been modified with a Nexus digital setting circle, which links wirelessly to my smartphone, and it is supported by a motorised tracking platform. I have also upgraded the spider vane with easy-to-adjust screws and added a Crayford 10x focuser for extra stability. Before the rebuild, the original scope was featured on The Sky at Night in Sir Patrick Moore’s garden. Chris Lintott loved it – if only he could see it now! Bernie Nicol, Southampton

Tell us about your scope! Email [email protected]

Tom Howard, Crawley, Sussex

Glad to hear that there was still a party atmosphere despite the weather, Tom. – Ed

values and laws should be imposed on it? American? Iranian? Australian? The list is endless and no doubt any such treaty would have to encompass all citizens on Earth. As we don’t have any active policing of the Moon, who is going to arrest those who break any law? Then there is the problem of extraterrestrial visitors. Should ET turn up on a mining expedition, I would suspect he would not give a lot of concern about any Earth-based agreement. Rob Thomas, Botcheston, Leicestershire

> The annual

Isle of Wight star party was clouded out

You’re right, Rob, it is a thorny issue that needs to be addressed alongside the science and engineering projects that will take us back to the Moon. – Ed

ET won’t care for our laws Are we blinded by success? The excellent article ‘Protecting our heritage in space’ in March’s Sky at Night Magazine (page 16) gave me much food for thought as I am a retired solicitor. While on the face of it, the situation as outlined by Lewis Dartnell [that there are objects on the Moon of significant cultural value, but no laws to protect them] would appear to offer a way ahead, I am afraid that there are a number of problems from the outset. Given that the Moon is increasingly being targeted by other nations, whose

I read the ‘Treasure trove of alien worlds’ news story in the March issue (page 12) with interest: it doesn’t seem that long ago that we were still debating if there were any other planetary systems out there! While the Kepler mission has been an enormous success and is providing masses of data for number crunching and citizen science for years to come, it seems to me there is a flaw in relying so heavily on this data when it comes to surmising the make up of exoplanetary systems. As Kepler uses the transit method to > skyatnightmagazine.com 2013

24

Bristol AS celebrates 70 years

The big debate @nichbar Cloud, cloud and then more cloud... but will keep on trying. @scarbastro Every night has been clouded out :( However, on 17th March the clouds were illuminated by aurora north of Scarborough :)

Members and guests recently celebrated the 70th anniversary of the Bristol Astronomical Society (BAS) during an evening dinner at the Old Bristolians Sports Club. The dinner was hosted by chairman Nigel Tasker, while guest of honour was the society’s new president, Prof David Southwood. During the evening, Maurice Brain, BAS’s longest serving member (he has seen 63 of its 70 years) recalled the formative era of the society. During early meetings, it was not permitted to ask a visiting speaker any question unless it was referred through the chairman. He also recounted how Sir Patrick Moore opened the Society Observatory in 1972 and offered memories of the founding of the Federation of Astronomical Societies. In his inaugural address to the society, Prof David Southwood then looked forward to the type of astronomy that BAS might undertake in the next 70 years. Finally, a 70th anniversary cake was duly produced and consumed. Chris Lee, deputy chair, Bristol Astronomical Society

> identify potential planets, there will always be a @andymorl69 Northeast skies couldn’t get any cloudier. @jowlymonster Constant cloud :( @richcollett I’ve got some cracking panoramas of clouds... @kevcoll69 Can it still be seen? @FelicityLennie Every night clear here. @davidhulme17 Comet – cloud hail snow rain!

preponderance of close-in planets. The problem I see is that we are being blinded by the obvious success of this mission and are missing the bigger picture. We have come so far in the last 20 years, but we are only just seeing the tip of one small iceberg. What we’ll know in another two decades, only time will tell, but I’m looking forward to the journey! George Futers, Peebles

The abundance of data from Kepler is helping astronomers to judge the relative abundance of exoplanets, for one thing. There are now more detection methods than ever before, including one that uses radio emissions from explanetary aurora, which we look at on page 106 of this issue. – Ed

Bishop’s brilliance Thank you for your feature on the English bishop who foretold modern cosmology (March issue, page 69). I knew of Georges Lemaître, the Belgian priest and astronomer who proposed the foundations for the model of an expanding Universe, but I wasn’t aware of Robert Grosseteste’s work. The feature arrived just as I was researching the Universe and space for my degree studies. My home city is Lincoln and 25 years ago I worked within Bishop Grossteste College and around the Bishop’s Palace, often coming across his name around Lincoln Cathedral. Deacon Ray Fox, Keighley, West Yorkshire

I’m delighted you found the feature useful, Ray. – Ed

The flame is lit I would like to thank you for running the article ‘Light revolution’ in the April issue (page 40). I’m sure this will promote discussions on the problem skyatnightmagazine.com 2013

Þ BAS members old and new celebrate another

decade of adventure; top, the celebratory astro cake

and future of light pollution. I hope the hobby can get a high-profile personality to champion the cause. For my part I will be writing to Nottinghamshire County Council to let them know of the article – I know they are keen to receive positive feedback on their programme to dim and turn off streetlights. Stephen Nickolls, via email

There have been many changes to streetlighting recently and it has been fascinating to research and bring these to a wider audience. – Ed

This is just the beginning Having just received the April issue of the magazine through my door this morning I would like to thank you for the new Binocular tour section (page 58). I currently do not own a telescope and often feel like I am missing out on what’s happening in the sky, so this is a fantastic inclusion for all of us binocular users. I can’t wait to get a nice clear night and try it out! I also love the new look of the magazine too. I’ve been a subscriber for nearly two years and just wanted to commend you and your team on the fantastic job you do every month. Amy Appleby, Darlington

Thanks Amy. Our new tour is here to stay, so those binoculars will get a good workout in the months to come! – Ed ......................................................................................... OOPS! On the two charts accompanying ‘15 great spring galaxies’ in March’s issue, the lines of declination were incorrectly labelled. On page 35, the 50º line should read 20º while the 40º line should read 10º; on page 37, the 40º line should be 20º, the 35º line should be 15º and the 30º line should be 10º.

LETTERS MAY 25

ASTRO CROSSWORD Number 36. Set by PERSEUS

Sky at Night Magazine is published by Immediate Media Company Bristol Limited under licence from BBC Worldwide.

EDITORIAL Editor Chris Bramley Features Editor Will Gater Production Editor Kev Lochun Editorial Assistant Kieron Allen Reviews Editor Paul Money ART AND PICTURES Art Editor Steve Marsh Picture Research Sarah Kennett CONTRIBUTORS Paul Abel, Sean Blair, Zach Cano, Adam Crute, Lewis Dartnell, Glenn Dawes, Russell Deeks, Lucie Green, Keith Hopcroft, Olivia Johnson, Carol Lakomiak, Pete Lawrence, Chris Lintott, Tom McEwan, Hazel Muir, Chris North, Jeff Parker, Andrew Phethean, Steve Richards, Govert Schilling, Paul Sutherland, Stephen Tonkin, Vincent Whiteman, Paul Whitfield, Paul Wootton ADVERTISING SALES Advertising Director Caroline Herbert Advertising Managers Steve Grigg (0117 314 8365), Tony Robinson (0117 314 8811) Inserts Laurence Robertson (00 353 87 690 2208) PRODUCTION Production Director Sarah Powell Production Manager Derrick Andrews Ad Services Manager Mel Watkins Ad Co-ordinator Fred Bennett Ad Designers Cee Pike, Andrew Hobson Reprographics Tony Hunt, Chris Sutch LICENSING Head of Licensing and Syndication Joanna Marshall

ACROSS 2 The Perseids peak in this month. (6) 6 Shooting stars from the Swan. (5,7) 10 Stars forge new elements in this process. (15) 12 The ____-major axis of an elliptical orbit is represented by the letter ‘a’. (4) 13 One of Sir Patrick Moore’s telescopes was a 5-inch _____ refractor. (5) 15 The main mirror or lens of a telescope is also known as the _________. (9) 17 Famous physicist born on Christmas Day (first name). (5) 18 International organisation that promotes the preservation of dark night skies (acronym). (3) 19 Formative period in the history of the Universe. (9) 22 The obsolete constellation of ‘Noctua’ represented this bird. (3) 25 Solar System in miniature. (6) 26 Parent planet of moons Dione and Tethys. (6) 29 Russian space station completed in 1996. (3) DOWN 1 ___ globules are dense, dark clouds of gas and dust. (3) 3 The counter glow – a tricky phenomena to spot even from a place with dark skies. (11) 4 The ___________ National Air and Space Museum, home of Apollo 11’s command module. (11) 5 Common eyepiece design. (6) 7 Auroral displays often contain this structure. (3) 8 Mothership to the Huygens probe. (7) 9 NASA’s new rocket system for manned exploration of the Solar System (acronym). (3) 10 Mission to study the distant edges of our Solar System, including the dwarf planet Pluto. (3,8)

11 He discovered the moon Triton (surname). (7) 14 Integral part of many specialist solar scopes. (6) 16 Icy moon of Saturn. (6) 20 Schmidt-Cassegrains are commonly attached to an altaz mount by a pair of ____ arms. (4) 21 There may be countless comets within this hypothetical ‘cloud’ around the Solar System. (4) 23 On balance this isn’t a particularly exciting constellation. (5) 24 The Fox ___ Nebula sits near the more famous Cone Nebula, in Monoceros. (3) 27 Unit that is roughly 150 million km (acronym). (2) 28 Time most commonly used when recording events (transits, eclipses, meteors, etc) in amateur astronomy (acronym). (2)

The solution to this crossword will be published in the June 2013 issue. Astro Crossword number 35 solution

MARKETING Head of Circulation Rob Brock Head of Marketing Marie Davies Marketing Executive Priscilla Midgley Head of Press and PR Carolyn Wray (0117 314 8812) PUBLISHING Publisher Andrew Davies Managing Director Andy Marshall MANAGEMENT Chairman Stephen Alexander Deputy Chairman Peter Phippen CEO Tom Bureau BBC WORLDWIDE MAGAZINES UNIT Managing Director Nicholas Brett Publishing Director James Hewes Editorial Director Jenny Potter Unit Co-ordinator Eva Abramik EDITORIAL ADVISORY BOARD Nicholas Brett, Tom Bureau, Deborah Cohen, Jane Fletcher, James Hewes, John Lynch, Jenny Potter, Kathy Sykes

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All rights reserved. No part of Sky at Night Magazine may be reproduced in any form or by means either wholly or in part, without prior written permission of the publisher. Not to be resold, lent or hired out or otherwise disposed of by way of trade at more than the recommended retail price (subject to VAT in the Republic of Ireland) or in mutilated condition. Immediate Media Company Bristol Limited is working to ensure that all of its paper is sourced from well-managed forests. This magazine is printed on Forest Stewardship Council (FSC) certified paper. This magazine can be recycled, for use in newspapers and packaging. Please remove any gifts, samples or wrapping and dispose of it at your local collection point.

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Sky at Night MAGAZINE

28

Hotshots This month’s pick of your very best astrophotos

PHOTO OF THE

MONTH

p The Horsehead Nebula

 Jupiter

SIMON TODD IRELAND, 23 SEPTEMBER 2012

RON ATKINS WORCESTER 12 DECEMBER 2012

Simon says: “I like the image because, of all the objects out there that are supposed to resemble something, this one stands out by far, with the dark nebulosity casting the shape of the horse’s head.” Equipment: Modified and cooled Canon EOS 500D DSLR camera, Astro-Tech AT8RC 8-inch Ritchey-Chrétien telescope, Sky-Watcher NEQ6 Pro mount Sky at Night Magazine says: “The Horsehead Nebula is never an easy target to image, but Simon’s shot portrays this

skyatnightmagazine.com 2013

iconic cloud of dust and gas superbly. The colours are very pleasing and the detail in nearby NGC 2023 is also excellent, especially considering this is a DSLR image.” About Simon: “I’ve been into astronomy since I was a child, from the age of 12. I took my first astrophotograph using a film camera back in 1999 – it was a picture of M42.”

Ron says: “I have attempted to image Jupiter many times before but the results were always disappointing. This time I spent a couple of nights star testing the scope to achieve the best possible collimation. I also allowed myself plenty of time to cool the scope down and used one of the moons to get the focus as sharp as possible.” Equipment: Imaging Source DFK 21AU04.AS CCD camera, Celestron C9.25 XLT Schmidt-Cassegrain telescope, Sky-Watcher NEQ6 mount

HOTSHOTS MAY 29

 Lunar halo JOE LYNCH WEST LOTHIAN, SCOTLAND, 25 DECEMBER 2012 Joe says: “I am fairly new to night-sky photography. Just after midnight I went out to my car to get a parcel from the boot when I saw this Moon halo. I grabbed my camera and tripod and headed away from the streetlights. I wanted a subject in the foreground so included the golf clubhouse. I was delighted with the result and intend to do more night shots.” Equipment: Nikon D300S DSLR camera, 15mm fisheye lens

 Stars over the Tungurahua volcano ROBERT DONALD GIBSON ZAPATA ECUADOR, 13 JANUARY 2010 Robert says: “I like this photo because it shows the power of light and creation inside our planet – the beauty of the Universe in communion with the mountains.” Equipment: Nikon D7000 DSLR camera, Nikon 70-300mm lens

Geminid meteors JOHN CHUMACK OHIO, US, 12 DECEMBER 2012 John says: “I was seeing one or two meteors every minute or so – definitely one of the best Geminid showers I’ve seen in over 20 years! My meteor video cameras at home also recorded over 150 bright Geminids.” Equipment: Modified Canon EOS Rebel XSi DSLR camera, 8mm fisheye lens

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 Solar prominence GARY PALMER SUTTON, SURREY 30 NOVEMBER 2012 Gary says: “The weather hasn’t been that good for solar imaging of late so it was nice to get a clear image of this unusually shaped prominence.” Equipment: Opticstar PX-137C camera, Coronado SolarMax II 3.5-inch solar scope, Celestron CGEM mount

 The Andromeda Galaxy JEFF BURGESS, MUSSELBURGH, 12 OCTOBER 2012 Jeff says: “This image was taken in one night and comprises 9.5 hours of exposures. It is my most detailed deep-sky image to date. It is also the first time I have been able to make out features in another galaxy, such as nebulae and star clusters.” Equipment: Modified Canon EOS 1000D DSLR camera, Celestron ED80 refractor, EQMOD-controlled NEQ6 Pro mount

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▲ The Orion and Running Man Nebulae SIMON DOWNS, CLANFIELD, 12 DECEMBER 2012 Simon says: “I’ve been told it’s difficult to get a bad image of M42. But with a wider field of view you can get really nice images of the fainter Running Man Nebula too! These two objects go together as nicely as bacon and eggs.” Equipment: Modified Canon EOS 550D DSLR camera, 4-inch Vixen refractor, hand-built English Yoke mount

HOTSHOTS MAY 31

▲ Star trails over Adraga Beach

 The Triangulum Galaxy

MIGUEL CLARO PORTUGAL 2 DECEMBER 2012

IAN RUSSELL SUTTON COURTENAY NOVEMBER 2012

Miguel says: “After the sunset, the sky takes on some fantastic colours with warm tones full of life. While waiting for nightfall I captured this star trail image that’s a little different from usual, where the different colours of the stars are clearly distinguishable.”

Ian says: “I am relatively new to astrophotography and even though I had seven hours of data this was quite a challenge to process. I’m pleased with the end result, particularly the detail in the dust lanes in the core.” Equipment: Atik 460EX monochrome CCD camera, Teleskop Service Optics 90mm apo refractor, Celestron CG-5 mount

Equipment: Canon EOS 50D DSLR camera, 16mm lens

ENTER TO WIN A PRIZE! We’ve teamed up with Astronomia to offer the winner of next month’s best Hotshots image a fantastic prize. The winner will receive a Celestron X-Cel LX 2x Barlow lens, a great accessory enabling you to boost the magnification offered by your eyepieces. www.astronomia.co.uk • 01306 640714

WORTH

£85

Email your pictures to us at [email protected] or enter online.

skyatnightmagazine.com 2013

As solar maximum approaches, the surface of the Sun will see more activity – but it could be a particularly weak peak

WHAT’S HAPPENED TO

SOLAR

MAXIMUM? It’s a solar maximum year, but the Sun has been unexpectedly quiet in recent months. Lucie Green takes a look at our star’s unusual behaviour

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SOLAR MAXIMUM MAY 33

ABOUT THE WRITER Dr Lucie Green is a solar scientist at UCL’s Mullard Space Science Laboratory, where she studies the Sun’s magnetic fields, and a presenter on The Sky at Night.

I

n 2007, a group of solar physicists known as the Solar Cycle 24 Prediction Panel looked to the future and made a bold prediction about what lay ahead for our star. Their task was to use observations and models of the Sun to analyse the Sun’s 11-year pattern of activity – the solar cycle – and predict when that cycle would reach a peak, a point known as solar maximum. Violent activity on the Sun – from energetic explosions known as solar flares to vast eruptions of material known as coronal mass ejections – follows the solar cycle, rising and falling in frequency along with the appearance of dark, cool regions in the Sun’s photosphere known as sunspots. Because of this, the sunspot cycle is often referred to as the Sun’s activity cycle. It was the panel’s job to study the sunspot cycle and give a prediction for the size and timing of the peak of the solar cycle that we are currently in – cycle number 24. After a great deal of study, the panel predicted that the Sun would be at its spottiest in 2011 or 2012. Our star, however, had other ideas. The panel made the 2007 forecast before the sunspots of cycle 24 had started to emerge. It was a difficult time to make a forecast: the previous cycle hadn’t yet ended and no new cycle spots had emerged to give an indication of future activity levels. The first sunspot of cycle 24 was seen on 4 January 2008; subsequent spots were slow to appear and so in 2009 the panel issued a revised statement that solar maximum would be delayed until this month, May 2013. Since then, however, the unusually low level of sunspots has continued. Now there are suggestions that solar maximum will occur later this year and that it will be a small maximum, probably the smallest for over 90 years. We won’t know for certain, though, until we are past this point and can look back.

So how did we get to the stage where we can predict the activity of our star and how does this apparent lull fit into our understanding of the Sun’s behaviour over much longer timescales? The answers to those questions lie further back in time. In western Europe, sunspots first attracted significant interest in the 1600s, when telescopes came into use. These early instruments provided a way to view and magnify the solar surface and astronomers such as Thomas Harriot, Christoph Scheiner and, most famously, Galileo Galilei were all intrigued by these blemishes on the otherwise dazzling Sun. Almost 250 years elapsed before a pattern in the number of visible sunspots was detected. Heinrich > skyatnightmagazine.com 2013

NASA/SDO

A brief history of sunspots

March 2011

September 2011

September 2010

March 2012

May 2010

September 2012

NASA/SDO X 2, SCHARMER ET AL, ROYAL ASTRONOMICAL SOCIETY/SCIENCE PHOTO LIBRARY X 2, NASA

> Schwabe, a German astronomer, had been

making observations of sunspots during his search for a planet that was then suspected to be orbiting the Sun closer than Mercury – he wanted to make sure he didn’t confuse the dark sunspots with the black disc of a transiting planet. But the sunspots distracted him from his planethunting quest and in 1843 he published a paper on a sunspot pattern that he thought he saw emerging. The number of sunspots seemed to be changing over time and had a cyclical nature – around every 11 years, the number of sunspots rose to a peak and fell back to its lowest number, he observed. Schwabe’s proposal sparked a new era in sunspot observations after the idea was picked up by the astronomer Rudolf Wolf. He convinced astronomers across Europe to make regular solar observations using the same scheme to classify and record what had been seen. It was Wolf who came up with the idea of a ‘relative sunspot number’, described by an equation that included skyatnightmagazine.com 2013

Þ The build up to solar max as imaged by NASA’s Solar Dynamics Observatory

a correction factor to account for instrument limitations and observing methods. In this way, Wolf initiated regular and more reliable sunspot observations, meaning that modern astronomers have a good record of solar activity dating back 150 years, in addition to the early but less reliable observations dating back to 1610.

The Sun goes quiet

Þ A sketch of sunspot activity made by Galileo Galilei in 1612

The reason why the 11-year sunspot cycle had evaded astronomers until 1843 can be explained to some extent by the fact that telescopic observations started during a weak solar cycle and that, for a while, the cycles seemed to disappear too. So few sunspots were forming on the Sun during that time that the cycles simply wouldn’t have been noticeable. Looking back over the historical data another German astronomer, Gustav Spörer, noticed this gap of around 70 years, when the sunspot cycle was interrupted. Spörer died in 1895, yet the idea that there was this unusual lull of solar activity

SOLAR MAXIMUM MAY 35

KEY

Monthly values (smoothed)

Monthly values

Predicted values (smoothed)

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SUNSPOT NUMBER

125

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75

50

25

0 YEAR 00

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Þ Sunspot activity since 2000, as well as current predicted activity levels to 2019; graph based on NOAA Space Weather Prediction Center data

“Spörer and Maunder showed that from 1645 to 1715, almost no sunspots appeared”

didn’t disappear thanks to the work of one man at the Royal Observatory Greenwich – Edward Walter Maunder. Maunder was interested in sunspot latitudes, displaying them in a graph now known as the ‘butterfly diagram’, below. Resembling the open wings of a butterfly, it shows that at the start of the solar cycle, sunspots are formed at about 30 º above and below the Sun’s equator. As the cycle progresses more sunspots appear, forming ever closer to the equator. Spörer and Maunder’s work established that from 1645 to 1715, virtually no sunspots appeared. The prolonged period during which the cycle seemingly ‘switched off’ now bears Maunder’s name – the Maunder Minimum. Modern technological advances have meant that the changing Sun can be monitored in more ways than by counting sunspots alone. Charged

Þ Edward Maunder, who mapped an unusual quiet period in solar activity

particles trapped along the magnetic field lines, emanating from sunspots, emit radio waves that have been recorded since 1947. These were first noticed during World War II, when radar equipment revealed radio emissions from the Sun’s atmosphere. The systematic measurements and scientific investigations this initiated were focused on solar radiation at a wavelength of 10.7cm. A great benefit of this 10.7cm emission, from a solar observer’s point of view, is that these radio waves penetrate through any clouds, which means observations can be made whatever the weather. These days it’s possible to gain a longer term view of solar activity through variations in the number of cosmic rays that reach us. Galactic cosmic rays are affected by the strength of the >

90ºN 30ºN EQ 30ºS 90ºS

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Þ The Maunder butterfly diagram, as produced by NASA’s Marshall Spaceflight Center to show sunspot activity from 1875 to the present skyatnightmagazine.com 2013

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NASA/SDO, PETE LAWRENCE, SOLAR MAGNETIC FIELD DIAGRAM BASED ON A GRAPHIC FROM NASA/ GODDARD SPACE FLIGHT CENTER, CONCEPTUAL IMAGE LAB

This June 2012 image of the Sun taken by NASA’s Solar Dynamic Observatory showed far fewer sunspots than had been expected

> Sun’s magnetic field and at times of solar maximum, when this field is at its strongest, fewer are able reach the Earth. These high-energy particles leave their calling card by producing the radioactive isotopes carbon 14 and beryllium 10 when they hit oxygen and nitrogen in the stratosphere; isotopes that are ultimately stored in tree rings and layers of snow. Despite uncertainties in the reconstruction of solar activity from this data, this gives us a way to look at the Sun’s activity over hundreds or even thousands of years.

solar cycles have been strong, to the extent that the Maunder Minimum appears to be an aberration in the Sun’s normal behaviour – yet it’s worth remembering that our sunspot observations through telescopes date back just 400 years, with reliable observations coming much later still. We are undoubtedly heavily biased by what we have seen during a tiny fraction of the Sun’s 4.5-billion-year lifetime. Nonetheless, there’s no denying that the familiarity of the 11-year cycle has meant that predictions of a particularly weak solar maximum for cycle 24 have sent ripples of excitement through the solar research community. The current solar cycle has presented an interesting challenge for those making predictions.

“We are heavily biased by what we have seen during a tiny fraction of the Sun’s lifetime”

An incomplete picture The sunspot record is, however, still our most complete archive of solar activity. In recent decades skyatnightmagazine.com 2013

SOLAR MAXIMUM MAY 37

THE SOLAR MAGNETIC FIELD

Þ Our star’s magnetic field is dipolar at solar minimum, far left, but becomes increcasing chaotic as activity builds to solar maximum, far right The Sun’s magnetic field is produced by the ‘solar dynamo’, which flips between two configurations. The first is a ‘dipolar’ magnetic field where field lines run parallel to lines of longitude and arc through the Sun’s atmosphere from pole to pole. This is the configuration at solar minimum. Flows inside the Sun draw out this magnetic field, as electrically charged gas rotates more quickly

at the Sun’s equator than at higher latitudes. The magnetic field gets wrapped around inside the Sun, creating zones of strong magnetic fields above and below the equator. Now, the magnetic field lines run almost parallel to lines of latitude and the second configuration has been reached. Portions of strong magnetic field become buoyant and rise up through the Sun, penetrating the

photosphere where they form sunspots. This happens most frequently at solar maximum. The reverse process back to solar minimum is not well understood. One possibility is that the magnetic field of the sunspots gets carried to the poles by a flow of gas. In this scenario, the flow would build up a dipolar field again, and with fewer sunspots emerging the Sun would return to the beginning of the cycle.

Such a low and delayed maximum was not expected by anyone and it is certainly exhilarating to see the Sun changing in this way. Today, we have a unique opportunity to watch this change happening with a fleet of telescopes and satellites. All the data being gathered now is crucial to learning more about the solar dynamo, which produces the Sun’s activity cycle. The solar dynamo is driven by moving gases inside the Sun. These gas flows carry with them the Sun’s magnetic field, dragging it around the Sun and causing the magnetic field to pulse in strength and complexity over the 11-year activity cycle (see ‘The solar magnetic field’, above).

Minimal cause for concern Intriguingly, studies of the long-term changes in the solar magnetic field suggest that quiet periods such as the Maunder Minimum may not in fact be so rare – it seems that during the Space Age we have just happened to catch our star acting up. The longterm view now taken by many scientists is that the spell of increased activity won’t last and that over the coming decades the Sun will come out of its ‘grand maximum’ and the subsequent cycles will continue to get smaller. These smaller solar cycles will undoubtedly have an effect on Earth and its climate. Although previous associations of the Maunder Minimum with a global mini-ice age have been grossly exaggerated, changes to winter weather patterns in western Europe do seem to occur at times of low solar activity. The physical mechanisms that lie behind this correlation are not yet properly

Þ A hydrogen-alpha scope will reveal prominences bursting from the Sun’s limb

understood, but the recent behaviour of the Sun is already generating significant research activity in this area in the UK. The solar maximum, whenever it arrives, is a chance to observe and enjoy our star. Sunspots are somewhat sparse, but views of the Sun through a specialist hydrogen-alpha-filtered telescope show prominences (huge clouds of material leaping from the Sun’s limb) and filaments (silhouetted prominences), so there is still plenty to see. A bonus feature of the Sun is that the most active sunspot regions actually tend to appear just after solar maximum. These regions produce the most energetic flares and eruptions, meaning that the declining phase of the cycle can be the most interesting. So don’t pack away your solar telescope just yet! S skyatnightmagazine.com 2013

ADVERTISEMENT FEATURE

Find the right one for you: buy your telescope from a specialist retailer

I

t is quite easy to become daunted by the vast array of equipment that is available to today’s amateur astronomers. Different makes, different models, different sizes and optical arrangements – if you’re new to the hobby, how do you make sense of all these details and fi nd the telescope that will show you the Universe?. The answer lies in buying from a specialist retailer – somewhere that really knows what they’re talking about. Like the retailers in this guide, they’ll have the practical knowledge that will guide you towards the scope that won’t end up gathering dust in a cupboard. Today there are over 1,000 models of telescope to choose from – refractors and reflectors, Dobsonians and Newtonians, Schmidtand Maksutov-Cassegrains. And just as important as the telescope is the mount it sits on; but do you go for equatorial or altazimuth, manual or Go-To? And what about accessories like eyepieces and finderscopes? That’s certainly a lot to consider before making a decision, but a specialist retailer will help you make that decision, taking important considerations like portability, construction and price into account. So if you need friendly, face-to-face advice and excellent aftersales service, free from biased opinions, specialist telescope retailers are the place to go for a helping hand through the technical literature and tables of figures. They’ll help you find a scope that combines quality and convenience at a price that’s right.

ADVERTISEMENT FEATURE

GREEN WITCH

TELESCOPE HOUSE

Green Witch is one of the UK’s leading suppliers of telescopes, binoculars and accessories for astronomy. Founded by former members of the Royal Greenwich Observatory in 1998, Green Witch is dedicated to helping you choose and use the equipment that is right for you. We also carry an extensive range of telescopes and binoculars for nature and leisure, which you are welcome to try before you buy. Whether you visit our showrooms or buy online you can be sure of excellent service.

Founded in 1785, Telescope House has been responsible for supplying many well-known Astronomers with telescopes and equipment. The late Sir Patrick Moore bought the majority of his telescopes from the company, including his very first instrument. With a friendly Showroom in Surrey, a number one-ranked retail website, and a service centre with fully qualified staff, the company offers equipment from manufacturers such as Meade, Revelation, Coronado, Bresser, Skywatcher, Orion USA, TeleVue, Vixen and Explore Scientific. Whether it’s advice on your first telescope, to setting up advanced Astrophotography systems, the staff at Telescope House have a wealth of experience and instant access to the right stock to back it up.

01924 477719 - Birstall, West Yorks 01767 677025 - Gransden, Beds & Cambs www.green-witch.com

ASTRONOMIA

SCS ASTRO

Astronomia’s stores in Surrey and London are home to the biggest range of telescopes and binoculars in the South of England. With over 50 telescopes and even more binoculars, Astronomia brings you the widest choice of respected brands and straightforward, honest advice. Buy from us and enjoy competitive prices, a 30-day money back guarantee and full-price trade-ins for 12 months on all telescopes!

SCS Astro’s Astronomy Shop has been trading since 1998 and is the South West’s leading retail outlet for Telescopes and Astronomical Accessories. Bristol, Exeter and Plymouth are all within easy travelling distance and parking is not a problem. We have a wide range of telescopes and accessories on display and are authorised dealers for Orion Telescope & Binocular Center, Burgess Optical, Tele Vue, Software Bisque, DayStar Solar Filters, GlareBuster, AstroArt, Celestron, Baader Planetarium, Skywatcher, Willman-Bell, EarthWin, HOTECH, Imaginova & AstroPix.

01306 640714 www.astronomia.co.uk [email protected]

ALTAIR ASTRO

01342 837 610 www.telescopehouse.com [email protected]

1823 665510 www.scsastro.co.uk [email protected]

THE WIDESCREEN CENTRE

Altair Astro are a manufacturer of high quality eyepieces, APO refractors and Ritchey Chretien or Cassegrain reflectors which are both visual and imaging capable. They are also distributor for iOptron products, including the SkyTracker DSLR mount, iEQ portable equatorials, and Minitower GOTO Alt-Azimuth mounts. Altair also manufacture their own mounting hardware and steel pier systems in the UK, and distribute the Canadian made SkyShed POD and POD Max observatory domes. Altair are able to offer complete systems from the ground up for amatuer astronomers taking their first steps, right up to schools, universities and professional institutions wanting custom research grade telescopes of large aperture.

London’s Astronomy showroom, located in Sherlock Holmes Territory off Baker Street – a family run business since 1971. Our experienced and knowledgeable staff offer quality, choice, expertise and service – see Celestron, Sky-Watcher, Meade, Orion, Tele Vue, and much, much more besides. “If the correct equipment is purchased it will give a lifetime’s enjoyment. This is our mission.”

01263 731505 www.altairastro.com

02079 352580 www.widescreen-centre.co.uk [email protected]

ROB GENDLER/WWW.ROBGENDLERASTROPICS.COM

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skyatnightmagazine.com 2013

PERFECT YOUR IMAGING APRIL 41 To capture images as impressive as this wide-field shot of Orion’s sword, you’ll need the right equipment

next

level

TAKE YOUR ASTRO IMAGING

TO THE

Steve Richards explores several ways you can go from capturing good astro images to great ones

A

strophotographers constantly strive to improve their images by whatever means they can – it’s in their nature to do so! These improvements normally come about in small steps made possible by using longer exposures, better processing techniques, improved focus, better tracking, more sensitive cameras, exotic filters and better optics. Each small change adds to the whole, so that better contrast is captured in dim galaxies and nebulae, sharper images with greater colour saturation are produced, star

shapes are improved and hitherto unseen features are revealed. So what do you need if you really want to take it up a notch? Here we detail some of the kit you can use to help take your astro imaging to the next level. ABOUT THE WRITER Steve Richards is an expert deep-sky observer and a dedicated astrophotographer, who compiles the Deep-sky tour every month.

If you’ve captured some great astro images lately, why not submit your best photos to Astronomy Photographer of the Year 2013? The world’s premier astro imaging contest is now open to entries. It showcases the best of the year’s astro images in categories including ‘Earth and Space’, ‘Deep Space’ and ‘Our Solar System’. Find out more at

www.rmg.co.uk/astrophoto

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GUIDING LIGHT The star Vega: an unguided five-minute exposure

Vega again: a guided five-minute exposure

One of the most important ways of improving your deep-sky images is by taking longer exposures to capture more detail. Doing so, however, puts greater demands on your mount, because it has to accurately track your target for longer periods of time. This is where autoguiding comes in – it’s a way of giving the mount a helping hand.

Autoguiding works like this: it uses a second camera whose sole job is to take a continuous series of short exposures of a chosen ‘guide star’ near to the object being imaged. The position of the guide star on the camera’s sensor is analysed and if the star starts to move in any direction, the autoguider issues a command to the mount instructing it to follow the star’s movement. This second camera can either be connected to a second telescope attached to the mount (a guide scope), or to the imaging telescope via an off-axis guider, right. Off-axis guiders use a prism to pick off a small sample of light from the very edge of the light cone that falls on the main imaging camera’s sensor. This sample is then diverted to the guide camera for analysis.

Þ Above: Sky-Watcher SynGuider autoguider; left: a typical off-axis guider If the corrections from the autoguider mean the guide star is accurately tracked, the imaging camera and telescope will also be tracking the sky accurately since both cameras are attached to the same mount. Guide cameras can be controlled by a laptop and guiding software, or operate on their own, like the Sky-Watcher SynGuider shown above.

SOUP UP YOUR SOFTWARE CAPTURING RAW IMAGE data is only half the equation in astrophotography. Processing the images to bring out all the best features of the object is equally important and just as time-consuming. Taking lots of images and then combining them in a process known as stacking produces high-quality images, by reducing the background image ‘noise’ and accentuating the best parts of the image data. The popular package DeepSkyStacker does an excellent job of this and is free, while more advanced (but costly) software packages such as MaxIm DL and Astroart add a whole raft

> MaxIm DL is an advanced image-stacking program of additional processing features to bring out the best in the data you have captured. These programs offer advanced features such as image sharpening, colour correction, saturation boosting, non-linear adjustment of the brightness levels and contrast adjustment. These features will enable you to extract the fine detail hidden within your data.

Adobe Photoshop is the de facto standard for adding the finishing touches to your images. This gives you access to a wealth of powerful image-processing tools and filters.

PAUL WHITFIELD X 6, STEVE RICHARDS X 5, THINKSTOCK

FINER FOCUS WITH A BAHTINOV MASK OUT OF FOCUS

IN FOCUS

Þ Careful adjustments alter the symmetry of diffraction spikes created by a Bahtinov mask skyatnightmagazine.com 2013

DEEP-SKY OBJECTS are relatively dim, and so are very difficult to focus on. However, using an elegantly simple device called a Bahtinov mask can simplify the task enormously. To use one, simply point your imaging telescope at a bright star near to the object that you wish to image, with the mask placed over the front of the telescope. The numerous cut-outs in the mask’s design produce a very specific set of diffraction spikes, in the same way that the spider

vanes of a Newtonian reflector cause a simple cross to appear on images of bright stars. However, instead of a simple cross the mask produces an X-shaped cross and a horizontal line. Adjusting the telescope’s focus while taking a continuous series of short exposures of the bright star causes the cross to move in relation to the horizontal line – when the line exactly bisects the cross, you have achieved perfect focus. If the star is in focus, any other deep-sky object will also be in focus.

PERFECT YOUR IMAGING APRIL 37

MAX OUT YOUR MOUNT Without doubt, the single most important component in an astro-imager’s arsenal is the mount. This vital piece of equipment supports the weight of the rest of your imaging equipment and moves it with precision so that it tracks the apparent movement of the sky, which is crucial for crisp astro images. It is important that the mount’s payload capacity is not exceeded – indeed the best tracking results are achieved with the mount operating at well under its rated capacity. If you are close to your mount’s payload capacity, now is definitely the time to upgrade to a larger, more capable mount. But it is not all about capacity. An upgraded mount could also introduce some valuable new features such as periodic error correction (PEC). PEC is a process in which the movements required to correct a mount’s periodic tracking errors are recorded over a single rotation of the tracking drive’s gears, then played back to automatically correct these errors in subsequent rotations. Upgrading your mount could allow you to take advantage of new drive technologies, utilising drive belts to eliminate manufacturing defects in the gear meshing found in conventional geared mounts. You could also consider friction drives, which have no gears or belts and rely on the contact of a driven spindle against a metal disk. This removes all backlash from the drive (that pause you sometimes get before the mount responds to a hand control input), ensuring very low periodic errors that are easy to correct with autoguiding. Easier autoguiding means a large degree of smoothing of the mount’s

movement. There are even direct drive mounts that have neither belt nor friction but are driven directly by an electric motor that forms part of the right ascension axis. All of these changes result in more accurate tracking, so stars in your images become sharper and better formed, more closely resembling perfect points of light. And if the stars are well formed, then the deep-sky objects themselves will also have greater fidelity. Upgrading could also allow you to dispense with your hand controller altogether and operate the mount entirely from your laptop using software. Planetarium programs, with their graphical user interfaces, make choosing and acquiring new targets a simple process using intuitive selection tools and mouse clicks. This type of mount operation is so much more enjoyable than having to plough through the menus on the hand controller to get to the object catalogues or mount functions that you want.

UPGRADE OPTIONS

Þ Upgrading your mount could give you more accurate tracking and sharper imaging

Sky-Watcher NEQ6 Pro

Avalon M-Uno

Paramount MX

Price: £960 Payload: 18kg Supplier: www.opticalvision.co.uk

Price: £3,999 Payload: 20kg Supplier: www.widescreen-centre.co.uk

Price: £7,498 Payload: 41kg Supplier: www.iankingimaging.com

This is the workhorse mount for many advanced imagers, as it provides unbeatable payload capacity for its price, responds very well to autoguiding and can be fully laptop-controlled using EQMod software.

With motors and electronics from the NEQ6, this mount offers full laptop control using EQMod and is built for use with Schmidt- or Maksutov-Cassegrain scopes. The backlash-free belt drive system never requires a meridian flip.

With a high payload capacity, negligible periodic error and laptop control using TheSkyX software, this is a serious telescope mount, and one that many astro imagers aspire to owning one day.

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SUPER SENSOR The CCD sensor in a camera has an array of electronic photoreceptors laid out in a grid of columns and rows. Photons falling on these receptors are converted into electronic charges, which are then read by the camera and their values recorded. More photons equal more electronic chargesv and represent greater light levels. Sensors with many receptors are able to record the varying light levels that fall on their surface and record these for processing into an image. DSLR cameras use large sensors (typically APS ‘C’ type, which are 22.2mm x 14.8mm in size) and because of economies of scale in their production they are amazing value for money, so it is no wonder that they’re a popular choice for deep-sky imaging. However, the sensors in DSLR cameras are very sensitive to infrared wavelengths of light, so manufacturers include a built-in infrared blocking filter on their sensors to tame this over-sensitivity. Unfortunately, these filters are rather wide in operation and they cut out some of the useful light wavelengths that are of interest to deep-sky imagers. Another problem with DSLRs is that all sensors generate heat in operation, and this heat produces a small amount of ‘noise’ in the images. This noise is not really noticeable in the short exposures (typically 1/60th of a second to 1/2,000th of a second) that DSLR cameras are designed for, but becomes very intrusive in the long exposures (typically five minutes or more) that are required for deep-sky imaging. Astronomical CCD cameras address both these issues head on. They are supplied

Þ Atik’s 314L is a good entry-level CCD camera without an infrared blocking filter installed, so that they are capable of recording a much wider range of wavelengths. Infrared is still unwanted for most deep-sky imaging purposes, however, so an external filter tailored for astronomy is used instead. Astronomical CCD cameras also have a device called a Peltier cooler installed behind

the sensor. This is a thermoelectric heat exchanger that cools the sensor down to a typical temperature of 25° to 30° below the ambient temperature, reducing sensor noise dramatically and making this type of camera very suitable for long exposures. Even if you already have a CCD camera, an upgrade may well be on the cards to acquire a larger sensor for wider fields of view.

UPGRADE OPTIONS

Atik 460EX

Starlight Xpress SXVR-M25C

SBIG STXL-11002

Price: £2,119 Pixels: 2,750 x 2,200 (12.49mm x 9.99mm) Supplier: www.green-witch.com

Price: £2,650 Pixels: 3,024 x 2,016 (23.4mm x 15.6mm) Supplier: www.widescreen-centre.co.uk

Price: £6,779 Pixels: 4,008 x 2,672 (36mm x 24.7mm) Supplier: www.iankingimaging.com

This popular monochrome CCD camera has a reasonably large sensor, yet can still accept 1.25-inch filters. It includes a Peltier cooler that chills it to 25° below ambient and also comes in a one-shot-colour version.

Matching the size of a typical DSLR camera sensor, this one-shot-colour CCD camera is perfect for wide-field imaging and can be brought down to 30° below ambient temperature with its Peltier cooler.

This top of the range monochrome CCD camera has a sensor that’s the same size as a single frame of 35mm film, an integrated filter wheel and Peltier cooling down to 60° below ambient temperature.

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PERFECT YOUR IMAGING MAY 45

NARROWBAND NIRVANA There are two ways of capturing colour images with modern cameras. A one-shotcolour CCD camera or DSLR will capture a full colour image in a single shot. Colour images can also be captured using a monochrome CCD camera, but this requires a different approach. With a monochrome (or ‘mono’) CCD you capture three sets of images through red, green and blue (RGB) coloured filters, then combine them later into an ‘RGB’ colour image in processing software. The big advantage of a mono CCD camera is that you can also image through a range of other types of filters to capture all sorts of extra detail. Standard RGB filters are known as ‘broadband’ filters but there are also various ‘narrowband’ filters available, the most popular being hydrogen alpha (Ha), oxygen III (OIII) and sulphur II (SII). These filters let through a narrow band of wavelengths corresponding to the light emitted by objects such as star-forming nebulae and planetary nebulae. By combining images taken through various narrowband filters, beautiful false colour images with exquisite detail can be produced. Another great by-product of using narrowband filters is that they filter out the

þ A small region of NGC 7000, imaged with narrowband filters, top, and RGB filters, bottom NARROWBAND

RGB wavelengths of light associated with most artificial lighting, enabling you to capture high-quality, light pollution-free data. The most common narrowband filter combination involves processing the final image so that the data captured through the SII filter goes into the red channel of an image, Ha to the green and OIII to the blue;

Ha/OIII mapping can be used to create images with natural-looking colours this process of ‘mapping’ the data to the colour channels produces the final full (false) colour image. Another mapping that works well requires only two sets of narrowband image data: Ha and OIII. By mapping Ha to the red channel and OIII to both the green and blue channels, very natural-looking colour images can be produced.

OPTIMAL OPTICS GOOD QUALITY OPTICS are vital in astrophotography to avoid chromatic aberration. These coloured fringes around bright objects are caused by different wavelengths of light being focused at different distances from the objective lens of refractors. Other issues include field curvature in refractors and coma in reflectors, both of which result in poorly shaped stars towards the edges of the field of view. Modern ‘ED’ refractors use special low‑dispersion glass elements to focus two wavelengths of light to the same point,

< The FLT 98 from William Optics is one example of a high-quality ‘apochromatic’ refractor

avoiding chromatic aberration. But the best results are achieved with a three‑element ‘apochromatic’ (apo) lens, which offers even better correction. Typical high‑quality apo refractors include the Astro‑Physics Starfire EDF, William Optics FLT 98 and Meade 6000 series.

Field curvature can be fixed with a field flattener, a device that fits between the camera and the telescope, but some refractors using a ‘Petzval’ lens arrangement, such as the Takahashi FSQ‑106ED, have field flattening built in. Coma is a natural effect of using a parabolic mirror such as those found in the best reflectors, but this problem can be easily resolved with by using a coma corrector.

ALTHOUGH DSLR CAMERAS can capture great deep‑sky images, the lack of red sensitivity caused by their infrared filters will eventually become a limiting factor. Fear not, these cameras can be modified for astrophotography. Common modifications include removing the infrared filter completely, or replacing it with a filter that passes the hydrogen‑alpha wavelength but cuts the unwanted infrared wavelengths. You can make either modification yourself,

but there are risks involved as a complete strip‑down of the camera is required, invalidating any warranty. However, various online resources explain the process in detail if you enjoy a challenge and accept the potential risks. Canon produces a version of its 60D camera called the 60Da that is suitably modified before leaving the factory, but

< Popular DSLRs such as this Canon EOS 40D lend themselves to user modification unfortunately Canon will not modify existing cameras for you. Luckily, several companies will carry out this work on Canon DSLR cameras for you, including Astronomiser in the UK, Baader Planetarium in Europe and Hutech in the US. Pentax Europe will also modify Pentax DSLR cameras. S skyatnightmagazine.com 2013

PAUL WHITFIELD X 3, STEVE RICHARDS X 3, ATIK, STARLIGHT EXPRESS, SBIG

MODIFY YOUR DSLR

THE SKY GUIDE MAY 47

May

The Sky Guide

Evening planets

Three bright planets will be jostling for position low in the west-northwest towards the end of the month. Mercury and Jupiter, pictured, will be joined by Venus, the most brilliant of the planets, creating a series of changing shapes from one evening to the next.

OUR STARGAZING EXPERTS PETE LAWRENCE As well as writing The Sky Guide, Pete can be seen on BBC TV’s The Sky at Night. On page 60, he explains how to image the entirety of globular cluster M13.

PETE LAWRENCE

STEPHEN TONKIN When he’s not doing astronomical outreach of one form or another, Stephen heads to the New Forest to observe the night sky. Take his Binocular tour on page 58. STEVE RICHARDS Steve is passionate about observing deep space and likes nothing more than taking images of distant galaxies – follow his Deep-sky tour on page 56 to find a host of fascinating objects. skyatnightmagazine.com 2013

48

HIGHLIGHTS Your guide to the night sky this month This icon indicates a good photo opportunity

1

WEDNESDAY At the start of May, Comet C/2011 L4 PANSTARRS will be passing between the constellations of Cassiopeia and Cepheus. If it follows predictions it will be around the 7th magnitude at this time and should be visible in binoculars.

2

4

THURSDAY  The Moon’s out of the way at the moment so this is a good time to take our Deep-sky tour. See page 56.

11

SATURDAY Look low towards the west-northwest this evening where brilliant Venus and Jupiter can be seen together, with the waxing crescent Moon (2% lit) sitting roughly between them. See page 50.

SATURDAY Globular cluster M3 is due south at an altitude of around 65º at 23:30 BST (22:30 UT). This magnificent but often overlooked object can be found roughly midway between mag. +2.9 star Cor Caroli (Alpha (a) Canum Venaticorum) and mag. +0.2 star Arcturus (Alpha (a) Bootis).

12

SUNDAY  Just after sunset, the waxing crescent Moon (7% lit) is just over 4º to the east of mag. –1.8 Jupiter. Mag. –3.8 Venus may also be visible close to the northwest horizon.

13

MONDAY Catch Comet C/2011 L4 PANSTARRS tonight as it passes mag. +3.2 star Errai (Gamma (g) Cephei) in the House asterism. The comet will probably be around 9th magnitude, so to see it you’ll need binoculars at least. It should remain close to the star for a few nights.

22

WEDNESDAY

The waxing gibbous Moon (93% lit) lies just south of the middle of a line between the mag. +1.0 star Spica (Alpha (a) Virginis) and mag. +0.4 Saturn tonight.

PETE LAWRENCE X 8

27

MONDAY Comet C/2011 L4 PANSTARRS is about as far north in the sky as it will get, around 5º from the north celestial pole. It should be around 9th magnitude at this time.

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FRIDAY  The waxing crescent Moon (37% lit) passes immediately to the south of the mag. +6.9 open cluster M67. The Moon will be due south of the cluster from 00:00 BST (23:00 UT on the 16th) until it sets.

23

THURSDAY  At 23:00 BST (22:00 UT), mag. +0.4 Saturn is due south with mag. +1.0 star Spica immediately to its right and brighter, mag +0.2 star Arcturus directly above it. The trio form a large right-angled triangle in the sky.

28

TUESDAY  Mag. –3.8 Venus, mag. –1.8 Jupiter and mag. –0.5 Mercury continue their show this evening, with Venus and Jupiter separated by 1º. Locate all three planets shortly after sunset.

30

THURSDAY 

Look out for bright orange Antares (Alpha (a) Scorpii) low in the south just before midnight. This red supergiant star shines at mag. +1.0. With no really bright stars around it, it stands out rather well.

THE SKY GUIDE MAY 49

What the team will be observing in May

6

MONDAY The Eta Aquarid meteor shower reaches its peak on the morning of the 6th. The shower has a decent peak activity count of 55 meteors per hour and is best observed in the early morning. The crescent Moon (14% lit) rises at around 04:00 BST (03:00 UT), but the encroaching dawn will bring the session to an end before then. See page 51.

Pete Lawrence “If Comet C/2011 L4 PANSTARRS is still fairly bright, I’ll be trying to image it at every opportunity. Since it is circumpolar right now, I’m not expecting to get too much sleep.” Chris Bramley “May marks the start of noctilucent cloud season so I’m going to be on the lookout for an early display. Their electric blue hue makes them very distinctive compared to lower altitude clouds.” Steve Marsh “I’ve decided to go on a globular cluster hunt this month in a bid to improve my skills at photographing deepsky objects. I’ll be heading straight for M13.”

Terms you need to know

18

SATURDAY Mag. –1.5 Mercury, mag. –3.8 Venus and mag. –1.8 Jupiter appear in a row after sunset. Look low in the west-northwest. Mercury marks the lower-right end of the line, Jupiter the upper-left end.

24

FRIDAY Mag. –0.9 Mercury, mag. –3.8 Venus and mag. –1.8 Jupiter form a right-angled triangle low in the northwest after sunset.

26

SUNDAY The three twilight planets form an equilateral triangle this evening. Mercury will have faded slightly to mag. –0.7, but should still be easy to find using the other two. Look for them low down close to the northwest horizon shortly after sunset.

31

FRIDAY Mag. +0.5 Saturn has been edging ever closer to mag. +4.2 Kappa (k) Virginis throughout the month. Tonight the pair will be separated by just 1.25º.

BRITISH SUMMER TIME(BST)/UNIVERSAL TIME (UT) Events are given in British Summer Time (BST), with Universal Time (UT) in brackets. BST is one hour ahead of GMT; UT is the same as GMT. RA (RIGHT ASCENSION) AND DEC. (DECLINATION) These co-ordinates are the night sky’s equivalent of longitude and latitude, describing where an object lies on the celestial ‘globe’.

Icons explained

How to tell what equipment you’ll need NAKED EYE Allow 20 minutes to become dark-adapted BINOCULARS 10x50 recommended PHOTO OPPORTUNITY Use a CCD, webcam or standard DSLR SMALL SCOPE Reflector/SCT under 150mm, refractor under 100mm LARGE SCOPE Reflector/SCT over 150mm, refractor over 100mm

Getting started in astronomy If you’re new to astronomy, you’ll find two essential reads on our website. Visit http:// bit.ly/10_Lessons for our 10-step guide to getting started and http://bit.ly/First_Tel for advice on choosing your first scope.

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DON’T MISS... 3 TOP SIGHTS Evening triple act WHEN: 12 May to 1 June, 22:00 BST (21:00 UT) from the centre of the UK. Times vary slightly with location.

MERCURY, VENUS AND Jupiter are all close to the Sun this month, so telescopically they’re off the menu. However, there are still sights to be had. If you have a clear and flat west-northwest horizon, you may be able to spot a rather lovely meeting of the trio this month, the three bright planets blazing away in the evening twilight. The show begins on 12 May when mag. –1.8 Jupiter can be seen hanging just to the right of the waxing crescent Moon (7% lit). If the sky is clear, it

should be visible just after 22:00 BST (21:00 UT) from the centre of the UK. Times will vary slightly depending on location and make sure that the Sun has set properly before you start looking. On 17 May, mag. –3.8 Venus should also be visible at around 22:00 BST (21:00 UT), having crawled away from the Sun’s glare just enough to be seen hanging low above the horizon. In the couple of days that follow, Jupiter and Venus move slowly closer together and are joined by mag. –1.4 Mercury,

The three planets will form an equilateral triangle at twilight on the 26th

which like Venus also appears to be moving away from the Sun. By the 24th, all three will be less than 5º apart. Mercury will have faded slightly by this time to mag. –0.9 but should still be easy to see thanks to the proximity of the other two, which retain their brilliance. The planets form a right-angled triangle low in the northwest at 22:00 BST (21:00 UT). The geometry continues on 26 May, when the trio move to

!

NEED TO KNOW

The planets of the Solar System all occupy similar orbital planes; it is this ‘co-planar’ nature that allow us to see conjunctions from our perspective on Earth.

form an equilateral triangle in the evening twilight. Two evenings later on the 28th, Jupiter and Venus will be in conjunction. On this evening both planets will be separated by 1º, with brighter Venus appearing to the north of Jupiter. Mercury Mercury Mercury Mercury Mercury, now mag. –0.5, 24th 26th 28th 31st Mercury Mercury will be visible above and Mercury Mercury Mercury Mercury Mercury Mercury Jupiter marginally to the left Mercury Mercury Venus of the other two. Venus Venus Venus Venus Jupiter Venus Jupiter Venus Venus Jupiter Venus Jupiter Venus Venus Venus Venus Venus As the end of the month Jupiter Jupiter Jupiter Jupiter approaches, all three planets Jupiter Jupiter Jupiter Jupiter form a distinctive line, low in the northwest after sunset. Moon Jupiter is now rapidly losing 12th 1/5 ground to the Sun and appears at the lower-right 31st 12th end of the line. Mag. –0.3 Mercury marks the upper28th Mercury 19/5 Jupiter left end while brilliant Venus 26th 31st sits right in the middle. 24th There’s no scientific 28th 24th relevance to this meeting 26th 26th of planets, but it is a great 28th 24th sight all the same. The trio 31st 19/5 are so bright that even though they’re located against a Venus bright evening twilight 19/5 19th 12th NNW sky, they should be fairly easy to pick out with just 1/5 your eyes. If not, binoculars will secure a view, but do make sure the Sun has well and truly set first. The positions of Mercury, Venus and Jupiter in May at 22:00 BST (21:00 UT), as seen from the centre of the UK PETE LAWRENCE X 4

iter Mercury

50

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THE SKY GUIDE MAY 51

PANSTARRS makes a House call COMET C/2011 L4 PANSTARRS continues its march across the night sky and has the virtue of currently being circumpolar as seen from the UK – it will be visible all night throughout the month. It is now fading fast, but should remain within the reach of a pair of binoculars for much of May. A small telescope should be able to pick it up with ease for the whole month. At the start of May, Comet C/2011 L4 PANSTARRS is close to the W-shaped constellation of Cassiopeia, the Seated Queen. Though it is technically within the borders of neighbouring constellation Cepheus, the King. The comet will remain in Cepheus until 25 May, when it passes

α

W

31 May

C/2011 L4 PANSTARRS

δ

WHEN: 1-16 May, all night

Errai γ

into Draco not too far from the pole star, mag. +2.0 Polaris. The comet heads towards the House asterism in Cepheus as mid-month approaches, passing close to the apex of the House’s ‘roof’, which is marked by mag. +3.2 star Errai (Gamma (g) Cephei). On the evening of 13 May, it passes the star at a distance of 0.25º – half the apparent diameter of the full Moon. If you can locate Errai, you should be able to use it to find the comet. The Moon starts to interfere with the view from the middle of the month onwards, so your best bet for spotting the comet is from the 1st to the 16th. C/2011 L4 PANSTARRS will reach Polaris at the end of May, passing the pole star at a distance of

γ α

URSA MINOR

Polaris

ε

6 May

26 May 21 May

16 May

11 May

1 May

Schedar House

β

DRACO ι β

CASSIOPEIA

ε δ δ

ζ

Alderamin

α

ε

μ

CEPHEUS LACERTA C/2011 L4 PANSTARRS will clip the House asterism on its way to Polaris

around 5º. At this time the comet will probably be at the limit for a pair of binoculars, so a telescope with a low-power eyepiece will give the best view.

Of course, the appearance of the comet is subject to change depending on how it performs compared to predictions in the run up to May.

DELPHINUS The shower’s radiant will be low in east; chart correct for 03:30 BST (02:30 UT)

The Eta Aquarids peak WHEN: 6 May, 02:30-03:30 BST (01:30-02:30 UT)

THE ETA AQUARID meteor shower peaks this month. This is a major annual shower with a peak zenithal hourly rate of around 55 meteors per hour. The shower is active from 19 April until 28 May, peaking at 02:00 BST (01:00 UT) on 6 May. Its radiant position at this time is close to the asterism known as the Water Jar – or its modern equivalent, the Steering Wheel – in the constellation of Aquarius, the Water Bearer. This region of sky doesn’t climb above the horizon until 02:30 BST (01:30 UT) and this is the best time to start watching. Dawn kicks in about an hour later, so the viewing window is short. You shouldn’t expect to see anything like the number of meteors suggested by the peak rate figure, as this shower is best

PEGASUS EQUULEUS Great Square of Pegasus

AQUARIUS π ζ

6 May

η

25 May Circlet

PISCES

β

α

20 Apr

γ

Steering Wheel

E

viewed from latitudes south of the UK. From our shores, the rate will be in single figures due to the low pre-dawn altitude of the radiant. Eta Aquarid meteors show fast and often bright trails. Brighter trails can also show the glowing aftermath of vaporisation known as a meteor train. With the radiant low in the sky, trails are likely to be quite

long. If you do spot an Eta Aquarid meteor, you’ll be watching a small part of Comet 1P/Halley vaporising in Earth’s atmosphere.

!

NEED TO KNOW

The zenithal hourly rate of a meteor shower is the expected number of meteors seen under perfect conditions with the radiant point of the shower overhead.

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52

THE PLANETS Pick of the month

SERPENS CAPUT

VIRGO

γ

SATURN

Zubeneschamali

BEST TIME IN MAY:

β

Saturn

LIBRA

1 May, 00:33 BST (30 April, 23:33 UT) ALTITUDE: 25º LOCATION: Libra DIRECTION: South

κ α

Spica

α

γ

Zubenelgenubi

CORVUS

RECOMMENDED EQUIPMENT:

3-inch telescope or larger FEATURES OF INTEREST:

Rings, brighter moons, occassional storms visible as white spots on the planet’s disc SATURN WAS AT opposition on 28 April and so remains well placed throughout May, staying visible all night long. At opposition, a planet finds itself on the opposite side of the sky to the Sun. This position also brings the planet closer to Earth and consequently it looks bigger and brighter than normal. Saturn is such a beautiful world to look at through a telescope; under good stable conditions it can appear magical. An icon for science-fiction buffs, the Ringed Planet has a fascination that cannot be beaten when viewed for real. There are three main rings that can be seen through a telescope, rather uninspiringly known as the A , B and C Rings. The outer A Ring and adjacent B Ring form the bulk of the ‘visual’ ring system and are separated by a thin dark

α

HYDRA

Antares

SCORPIUS

S Saturn is visible all night throughout May, slowly moving towards an encounter with Kappa Virginis

gap known as the Cassini Division. The C Ring, sometimes called the Crepe Ring, lies inside the B Ring and is a very diffuse feature. It is visible with a 6-inch telescope when the seeing is good. It is somewhat easier to see if the rings are tilted open, as they are at present. Saturn’s disc can appear fairly bland at first glance, but does give up detail if you give it time. It is banded like Jupiter, but the belts are far more subtle than those found on its fellow gas giant. From time to time, white spots – massive storms in the planet’s atmosphere – also reveal themselves against the subtle hues of the disc.

The stark Cassini Division separates the A and B Rings

Mag. +0.4 Saturn currently resides in Libra, but is slowly moving towards Virgo for a close encounter with mag. +4.2 star Kappa (k) Virginis in July. It crosses the border into Virgo on 13 May.

How the planets will appear this month The phase, tilt and relative sizes of the planets in May. Each planet is shown with south at the top, to show what it looks like through a telescope

MERCURY 1 MAY

SATURN 15 MAY

VENUS 31 MAY

URANUS (NOT VISIBLE) 15 MAY

PETE LAWRENCE X 2

MERCURY 15 MAY MERCURY 31 MAY

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MARS (NOT VISIBLE) 15 MAY

NEPTUNE (NOT VISIBLE) 15 MAY JUPITER 15 MAY

0”

10”

20” 30” 40” ARCSECONDS

50”

1’

THE SKY GUIDE MAY 53

JUPITER BEST TIME IN MAY:

1 May, 22:00 BST (21:00 UT) ALTITUDE: 15º LOCATION: Taurus DIRECTION: West-northwest Jupiter is no longer a serious telescopic target because it is too low in the sky after sunset, embedded in the bright evening twilight. The planet can still be seen with the naked eye, low down in the westnorthwest after the Sun has set. It’ll be easier to see at the start of the month but if you can stay with the planet throughout May, there’s a treat in store. As the inner planets Venus and Mercury appear to crawl away from the Sun, they will meet Jupiter going in the opposite direction. See page 50 for more about this low but spectacular conjunction. MERCURY BEST TIME IN MAY:

26 May, 21:40 BST (20:40 UT) ALTITUDE: 9º LOCATION: Taurus DIRECTION: West-northwest Mercury’s not well placed at the start of May, but becomes better positioned as we head towards the end of the month. The reason is that it is heading towards greatest eastern elongation, which occurs on 1 June. On that date the planet will appear to be separated from the Sun by 24º. Coming back to this month, Mercury will probably be first visible around 18 May, when it will be a bright mag. –1.5 and quite close to brilliant mag. –3.8 Venus. Both planets and Jupiter should be visible low in the northwest following sunset given good clear skies. Over the next few days, Mercury will slowly dim. On the 24th the planet will be mag. –0.9, but just less than 1.5º from Venus. The more

brilliant Venus acts as a useful signpost, appearing out of the twilight before Mercury can be seen. Some interesting patterns will occur between Venus, Jupiter and Mercury during the last week of the month – see page 50. By 31 May, Mercury will still be bright, but will have faded to mag. –0.3. If you can get a look at it through a telescope, the planet will be showing a 63% lit waning gibbous phase at this time. VENUS BEST TIME IN MAY:

26 May, 21:40 BST (20:40 UT) ALTITUDE: 9º LOCATION: Taurus DIRECTION: West-northwest Venus is an evening object but still quite close to the Sun at the start of the month. Consequently, it sets quite soon after sunset at the beginning of May. The planet’s separation from the Sun increases throughout the month – by the end of May it will set approximately 90 minutes after sunset. The planet’s brightness stays fairly constant throughout May at mag. –3.8. This allows it to punch through the evening twilight and it should be fairly straightforward to spot as long as you have a good flat west-northwest horizon from the middle of the month onwards. Venus is joined by its inner Solar System companion Mercury and gas giant Jupiter towards the end of the month. Despite the fact that this meeting will occur against a bright twilight sky, it’s certainly one that’s going to be worth looking out for. See page 50. NOT VISIBLE THIS MONTH MARS, URANUS, NEPTUNE

See what the planets look like through your telescope with the field of view calculator on our website at: http://www.skyatnightmagazine.com/astronomy-tools

Saturn’s moons Using a small scope you’ll be able to spot Saturn’s biggest moons. Their positions change markedly during the month, as shown on the diagram below. The line by each date on the left represents midnight.

SATURN IN MAY DATE

WEST

EAST

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 3

2

1

0

1

2

3

Arcminutes

Tethys

Dione

Rhea

Titan

Iapetus

Saturn

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Sch

ed

δ W

ar

α

CASSIOPEIA γ

T

RT O N

β

H E AS T

M52

CEPH

α

EUS

δ

When to use this chart

1 May

House

C/2011

γ

LACERTA

M103

NORTHERN HEMISPHERE

15 M

β T

α

On other dates, use the interactive planetarium on our website at www.skyatnightmagazine.com/interactive-planetarium

μ

M3 9

1 MAY AT 01:00 BST > 15 MAY AT 00:00 BST > 31 MAY AT 23:00 BST

mi era Ald

How to use this chart D

n

en e

δ

b

α

31 May

γ 9

le ng Tri a er

Cros

S

ern

11 May 2013

06:09 BST

22:30 BST

21 May 2013

16:38 BST

02:58 BST

31 May 2013

01:13 BST

12:32 BST

X

5

DA

4

M1

AU

3

SUNDAY

SC EN

2

SATURDAY

SCUTUM

1

FRIDAY

γ

RP SE

α

WEDNESDAY THURSDAY

β

RS

4

β

γ

IUC

M1

9

10

11

12

NEW MOON

13

14

15

16

17

18

19

20

21

22

23

24

25

26

δ β

M1

α

2

5

M

Celestial Eq uator 7

S EA

CHART CONVERSION BY PAUL WOOTTON

8

H UT SO

7

T

10

M

25

β

th

γ

FULL MOON

27

28

29

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30

31

β

γ

Rasalgethi

HUS

α

γ

β

OPH

δ

R

0

6

CORONA BOREALIS

R

Moon phases in May TUESDAY

H

α α

Times here are given for the centre of the UK.

MONDAY

OP

ULE Keystone S δ

T

10:54 BST

RC

SC APU

MOONSET

01:43 BST

β

SER PEN

MOONRISE

01 May 2013

γ

Su

DATE

α

21:27 BST

M13

gue

04:48 BST

T

Rasalha

31 May 2013

β

21:13 BST

M57

05:00 BST

2

10

M

M92

HE

AQUILA

21 May 2013

a

9

20:57 BST

o

39

20:40 BST

05:16 BST

Ve g

er

05:35 BST

11 May 2013

re

γ

C olli nd

01 May 2013

δ

SUNSET

VULPECULA α

α β

γ

SUNRISE

air

Al

bi

δ

SAGITTA

DATE

β

The Sun and Moon this month

Alt

LYR A

δ

β

M71

γ α

EAST

1. HOLD THE CHART so the direction you’re facing is at the bottom. 2. THE LOWER HALF of the chart shows the sky ahead of you. 3. THE CENTRE OF THE CHART is the point directly over your head.

DRA

s

mm

δ

Nor th

S DELPHINU α

CYGNU

M2

SCORPIU M80 S α

4 An M tar es

β δ

LIBRA

NORTH

THE SKY GUIDE MAY 55 α

δ

k

irph a

Key to star charts

PERSEUS γ te r us Cl

M la

N

A

α

IG

AU R

Do

ES T

β

β

γ

α

δ

GALAXY

D AR OP

RR

S ALI

CONSTELLATION NAME

O

RT HW

le ub

pel

Ca

1 L4 PANSTARRS

STAR NAME

OPEN CLUSTER GLOBULAR CLUSTER PLANETARY CLUSTER

L M

82

M81

δ

ll

MOON, SHOWING PHASE

STAR-HOPPING PATH

LEO

α

α

tic

Ec lip

β

BINOCULAR FIELD OF VIEW

y -sk

57

r, p

tou

ep

Porrim

De

a

δ

ER AT

4 10

M

α

US

RV

CO

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γ β

γ

MILKY WAY

α

TELESCOPIC FIELD OF VIEW

S

δ

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22

α

5 M1 0

th

r

α

S

ES T

γ

MAG.0

N TA

19

δ

VIR

Alphard

BRIGHTER THAN MAG. 0

X SE

M61

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QUASAR STAR BRIGHTNESS:

UT HW

m de

Sp

M96

Denebola 0

M98

M49

Regulus

PLANET

M95

δ

ε

x

tri

ia

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Saturn

ASTERISM

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52

HYDRA

γ 48

C

65 M 6 6 M

M9 M91 9 M86 M90 M87 M59 M58 M60

α

N

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β

M53

M 10

Arc turu

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M64

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METEOR RADIANT

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β

β BE COM RE A NI M CE 88 S

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γ

M3

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M6

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α δ 16th

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LEO

Mizar

γ

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M101

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δ

ba

δ

α Thu

β

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ASTEROID TRACK

α

α

β

SA R UR JO A M

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Dubhe

CANCER

COMET TRACK

ab

β

VARIABLE STAR

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DOUBLE STAR

β

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X LYN

δ U M RS IN A O R

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DIFFUSE NEBULOSITY S

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Po

GEMINI

ME CA

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May

γ

HYDRA

β

α

US

TAUR

CEN

SOUTH

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DEEP-SKY TOUR With Steve Richards

Markarian, this feature stretches across the heart of the region known as the Realm of Galaxies – originally called the Realm of Nebulae before the true nature of galaxies was known. With an 8- to 10-inch telescope, a gentle sweep in a south to southwest arc takes in a host of wonderful galaxies, including NGC 4474, 4468, 4459, 4477, 4473, 4461, 4435 and 4438. The chain ends with the spectacular M84 and M86.  SEEN IT

See off spring with our valedictory tour of the gems in Coma Berenices and Virgo ✓ 

Tick the box when you’ve seen each one

Markarian’s Chain appears as a cascade of galaxies that decorate Queen Berenice’s hair

CHART AND PICTURE: PETE LAWRENCE

1

2

3

MARKARIAN’S CHAIN

M88 is an excellent marker for locating our next ‘object’, the trail of galaxies known as Markarian’s Chain. Named after Armenian astronomer Benjamin E

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Our third delight is bright elliptical galaxy M60 – you should be able to spot it about 1.5° northnortheast of mag. +4.9 star Rho (ρ) Virginis. Through a 6-inch telescope, M60 appears slightly egg-shaped with an almost stellar core. Johann Gottfried Koehler discovered it while comet hunting in April 1779, but by coincidence Charles Messier spotted it just four days later. It also appears in Arp’s catalogue of peculiar galaxies because another object – spiral galaxy NGC 4647 – can be seen overlapping it in images. This second galaxy is 2.5 magnitudes dimmer than our target.  SEEN IT

4

M61

5

PORRIMA

M88

This month is an excellent opportunity to say farewell to some spring galaxies before they disappear, so we start our tour in Coma Berenices with one of the brightest in the Virgo Cluster, M88. This spiral galaxy appears as an elongated ellipse just over 7 arcminutes across, tilted at 30° from our perspective on Earth. A 6-inch telescope will easily reveal it as a hazy oval patch around a somewhat brighter core, while a 12-inch telescope at 250x magnification will start to show its spiral structure. To locate M88, imagine a line between mag. +2.9 star Vindemiatrix (Epsilon (ε) Virginis) and mag. +2.1 star Denebola (Beta (β) Leonis). Sweep 2° north just before the halfway point to find it.  SEEN IT

M60

6

From M60, draw a line towards mag. +3.9 star Zaniah (Eta (η) Virginis). About three-quarters of the way along, sweep 2° northwest to find our next stop, spiral galaxy M61. This galaxy appears face on from Earth and has tightly wound spiral arms which, through a 6-inch telescope, take the form of a circular patch of light surrounding an almost stellar core. A 12-inch telescope will start to reveal the spiral arms in tantalising detail and may hint at the central bar running through the galaxy from north to south.  SEEN IT

Continue on to Zaniah then follow the constellation eastwards to reach beautiful but close mag. +2.7 double star Porrima (Gamma (γ) Virginis). This pair of yellow-white stars orbit one another once every 169 years. In 2005, they were at their smallest apparent separation of 0.4 arcseconds, making them very hard to split. However, the separation has been increasing year after year and is currently approaching 2 arcseconds, so you should be able to resolve the individual stars in a 6-inch telescope. The separation will continue to increase until 2089, when the two stars will be nearly 6 arcseconds apart – so the sooner you try this one the better if you enjoy a challenge!  SEEN IT

CALDWELL 52

Our final object this month is lenticular galaxy Caldwell 52 (also designated NGC 4697), which was discovered in April 1784 by William Herschel. One of the brightest galaxies in the night sky, it can be found by sweeping 4.7° southeast from Porrima. Caldwell 52 appears as a smooth, hazy, elongated patch of light with a bright and sharply defined core when viewed through a 4-inch telescope. A 10-inch telescope will reveal several regions of varying brightness in grainy bands around a brighter, almost stellar core.  SEEN IT

0m

0m

12h0

+20º

12h3

13h0

13h 30m

0m

+25º

M64

COMA BERENICES

M53

α

+25º Melotte 111

Diadem

5°

+15º

M85

1

M88

+10º

ε

Vindemiatrix

3

M87

VIRGO

+20º

2.5°

W

NGC 4468

NGC 4474 M90 NGC 4647 NGC 4477 NGC 4473 NGC 4461 M60

E

N

M100

S

NGC 4459 NGC 4435

2 Markarian’s Chain

M86 M84

Denebola

β

NGC 4388 NGC 4438

ρ

+15º

LEO

Realm of Galaxies

+5º

M49

+10º

ο Auva

δ

13h0 0m

0º

Celes

ν +5º

tial E

γ

-5º

4 M61

NGC 4636

quato

r

Porrima

5

ξ

π

Zavijava

Zaniah

η

β

Ecliptic

6

0º

11h3

0m 12h0

-10º

12h3

0m

0m

NGC 4697

-5º

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N EW

Cephei, also named the Garnet Star by William Herschel, who observed it in 1783. Herschel’s description of how to appreciate the star is as appropriate today as it was when it was written: “of a very fine deep garnet colour and … a most beautiful object, especially if we look for some time at a white star before we turn … to it, such as a Cephei, which is near at hand”. This red supergiant is one of the largest stars known: Jupiter would orbit inside it!  SEEN IT

BINOCULAR TOUR With Stephen Tonkin Take in the first of 2013’s comets, the most famous variable star and more

1 M52

3 DELTA CEPHEI

10 x The variable star that gave its name to an 50 entire class of stellar bodies – the Cepheid Variables – Delta (d) Cephei swings from mag. +3.6 to mag. +4.5 over a period of 5.37 days. In the 20th century Henrietta Swan Leavitt used Cepheid Variables to demonstrate the periodluminosity relationship, which allowed them to be used as the first ‘standard candles’ for measuring the size of the Universe. Delta Cephei is not only here for that reason, though: it is a beautiful binocular double, with a deep yellow primary star and a blue secondary.  SEEN IT

2 C/2011 L4 PANSTARRS

10 x Comet C/2011 L4 PANSTARRS is predicted 50 to be at mag. +7.6 at the beginning of May, falling by nearly two magnitudes during the month as its distance from us increases from 1.54 AU to 1.85 AU. On the night of the 13th, it passes less than 0.5º from mag. +3.2 star Errai (Gamma (g) Cephei). See how long you can follow the comet before it fades from view. This will be excellent practice for the coming autumn and Comet

URSA MINOR

26 May Polaris

6 NGC 7160

15 x Mag. +6.1 open cluster NGC 7160 is 70 visible in the same field as the Garnet Star, but on the opposite side of the Alderamin-Zeta Cephei line. Look at it directly and it appears almost like a globular cluster; averted vision reveals it to have an oval shape, with two brighter stars near the centre. The brighter of these is the slightly variable contact-binary star EM Cephei, which varies from mag. +7.0 to mag. +7.2. Contact binaries are, as the name suggests, stars that are so close together that they touch.  SEEN IT

4 THE GARNET STAR

10 x Just west of the mid-point of the line 50 between mag. +2.5 star Alderamin (Alpha (a) Cephei) and mag. +3.4 Zeta (z) Cephei is a distinctly red-orange object, mag. +4.2 Mu (m)

31 May

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10 x Just over 1º south of the Garnet Star is 50 mag. +3.5 open cluster IC 1396. It’s an ideal 10x50 binocular object, being over 1º wide and appearing as a more star-dense part of the Milky Way. It is associated with some nebulosity, the Elephant’s Trunk Nebula, that can just be seen in 15x70 binoculars, especially if you hold an ultra-high contrast filter over an eyepiece. On a dark, transparent night, averted vision may enable you to see some brightness variation in the background sky: that is the nebula.  SEEN IT

C/2012 S1 ISON, which is predicted to be of a similar magnitude by mid-October.  SEEN IT

10 x Mag. +6.9 M52 is a small and compact 50 star cluster of nearly 200 stars. Not only is it shaped like an arrowhead, but it also lies within a north-pointing arrowhead of stars – the north tip is mag. +5.0 4 Cassiopeiae, while the other points are filled by a pair of 7th-magnitude stars. Find the cluster by drawing a line from mag. +2.2 star Schedar (Alpha (a) Cassiopeiae) to mag. +2.3 star Caph (Beta (b) Cassiopeiae) and continuing onwards – you’ll soon reach M52.  SEEN IT

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5 IC 1396

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4 CHARTS AND PICTURES: PETE LAWRENCE

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THE SKY GUIDE MAY 59 N

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METIUS

FABRICIUS

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JANSSEN FABRICIUS A

JANSSEN K

Janssen

JANSSEN L

STEINHEIL WATT

TYPE: Ancient crater SIZE: 180km wide AGE: Between 3.9 to 4.6 billion years old LOCATION: Latitude 45°S, longitude 41°E BEST TIME TO OBSERVE: Five days after new Moon (evening of 15 May) or four days after full Moon (after 01:00 BST on 29 April) RECOMMENDED EQUIPMENT: 10x binoculars

Crater Janssen is so old and eroded that it is not really clear where its northern wall actually is

MOONWATCH With Pete Lawrence “Overlap logic is used to determine relative age right across the Moon’s surface. If something lies on top of something else, it must be younger” SOME LUNAR CRATERS, such as Tycho and Copernicus, are extremely well defined with sharp circular walls. These features are often relatively young, formed in the past billion years or so. Older features don’t tend to fare so well, having been degraded over time so that their borders become indistinct. Crater Janssen is a classic example of an old crater that has been so heavily eroded that at times you can only see a hint of its full form. It lies in the southeast quadrant of the Moon’s near side, nestled in the lunar highlands. It’s easiest to find it using a set of younger craters that lie either nearby

or interrupt Janssen’s walls. To the northeast are 80km-wide Fabricius and 90km-wide Metius, two distinctive craters that appear to be just touching. Southeast are 70km-wide Steinheil and 68km-wide Watt. Steinheil overlaps Watt, intruding halfway into the slightly smaller crater. These overlaps provide evidence of age: Watt must be older than Steinheil for the craters to appear this way. Overlap logic is used to determine relative age right across the Moon’s surface. If something lies on top of something else, it must be younger. In the case of 180km-wide Janssen, this process is taken to extreme and its somewhat hexagonal outer walls are really quite

broken in parts. Crater Fabricius cuts through what appears to be the northeast rim of Janssen completely. I say ‘appears’ deliberately – Janssen is so eroded to the north that it is not entirely clear where its northern boundary runs. There are three curved ridges that could fit the bill. The crater’s floor is relatively smooth, with a number of smaller craterlets including 16km-wide Janssen K and 12km-wide Janssen L. A curved rille runs from the southern edge of Fabricius and turns past the western flank of the central mountain complex. The rille thins as it curves round to reach Janssen’s southern rim. South of Fabricius and continuing the interruption to Janssen’s rim is 45km-wide Fabricius A. This crater is also distorted, its southern rim appearing very indistinct, almost opening out to join with the floor of Janssen itself. Janssen is also interrupted by the 36k-wide Lockyer, a defined crater with a flat floor and steep walls. You’ll get the best views of Janssen when the lighting is oblique, which occurs around five days after new Moon or four days after full. If you can get a look at the crater, try to work out where its northern boundary lies. It is not as easy as you might think. skyatnightmagazine.com 2013

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ASTRO PHOTOGRAPHY With Pete Lawrence

M13 in Hercules Recommended equipment Monochrome CCD camera, telescope, driven equatorial mount, autoguider, graphics editor

THERE’S A RATHER remarkable object in the constellation of Hercules, designated M13, but also known as the Great Globular in Hercules. It is, as its name suggests, a globular cluster. This compact sphere, less than 150 lightyears in diameter, contains several hundred thousand stars. It is the northern hemisphere’s showpiece globular – hence its epithet, ‘Great’. Imaging M13 isn’t too hard. The centre is bright and quite easy to see through the viewfinder of a camera attached to a telescope. Indeed, there are many images of this cluster online, which isn’t a huge surprise as its brightness and beauty makes it one of the most common springtime objects to photograph. However, capturing its faint outer reaches is more of a challenge.

Just visible to the naked eye, M13 appears as a fuzzy star in binoculars. A small telescope will start to reveal the form of the cluster; the larger you go in terms of aperture, the more impressive it will become. M13’s component stars all orbit around the cluster’s common centre of gravity and we see these stars as a collection that increases in density – and therefore brightness – towards the centre. There are two fairly bright stars close by that act as marker for the size of the cluster: mag. +6.8, TYC 2588-2833-1 and mag. +7.3, TYC 2588-1571-1. Many images of M13 also include these stars. Look for them and you’ll be able to see whether an image captures the full extent of the cluster. Most shots only capture just the core of M13, a tiny element of the whole

object. Longer exposures go deeper, revealing more of the fainter stars lying outside the core, exposures that are lengthier still can show that the cluster is very large indeed; certainly much larger than the usual core-only shots. In its full majesty, the fainter outlying regions of M13 almost fill the distance between those two bright marker stars. Remarkably, this gives M13 an apparent diameter roughly the same as that of the full Moon.

Forward planning So how do you capture the entirety of this object? If you are just imaging the core, its brightness makes it fairly easy to record. However, if you want the outlying fainter stars as well, there’s a problem: the exposures you need to capture them will inevitably overexpose and burn out the core. It’s possible to overcome this by combining separate exposures of the outer stars and inner core, and blending them together with image processing software. This creates an image with a much larger dynamic range than you’d normally be able to get out of a camera. To reveal the faint stars of M13 you will need to take shots that are at least tracked and preferably autoguided. Tracking means the mount’s right ascension axis is driven to compensate for the apparent motion of the night sky due to Earth’s rotation and prevents stars from trailing. A well-aligned equatorial mount may well be able to track for a couple of minutes before exposures start to show deformed star shapes, but limits of 30-60 seconds

ALL PICTURES: PETE LAWRENCE

Combining monochome CCD images

STEP 1 We’ll assume you’ve already managed to take images of M13 through a telescope and a monochrome CCD camera, using a shorter exposure for the core and a longer one for the outer stars. The actual exposure time you need will depend on your setup, but aim to cover the regions shown in our example images above.

skyatnightmagazine.com 2013

STEP 2 The shots should be calibrated and stacked; DeepSkyStacker is excellent software for this task as it has a lot of help files to guide you through the processes required. At the end of this step you should have two calibrated images, one showing the core and the other with an overexposed core but showing the fainter stars.

STEP 3 Load each calibrated shot into a layer-based graphics editor such as GIMP or Photoshop. Adjusting the Levels and Curves tools may help to bring out the fainter stars in the longer exposure; typically, the dark part of these tools will address the outer stars, while the part dealing with light pixels will help to keep the core looking right.

THE SKY GUIDE MAY 61

Our final, full image of M13, flanked by its two marker stars; the Propeller is also visible in the core

are more common. This is why most shots of M13 only show the core. A short, 30-second tracked exposure will normally be able to record the cluster without significant trailing, but this is too short to capture the faint outer stars, which end up hidden in the background image noise. Our guide below shows you how to combine monochrome CCD shots, but the technique will also work with colour DSLR images. DSLR images have a tendency to show M13 as blue or even green, a result

STEP 4 Copy your edited shots into a new image, placing the one exposed for the outer stars on a layer above the one exposed for the core. Make the upper layer semi-transparent and adjust its position so it lines up with the lower layer. Make the upper layer opaque again when done. Both layers should now be identically aligned.

of the infrared filter built into many commercial cameras; this skews the colour balance away from the red end of the spectrum. This is something to watch out for when processing the image: adjust it with the colour balance tool. M13’s core is crossed by three slightly darker lanes that meet at a central point. This gives them the appearance of a three-vaned wind turbine that has been nicknamed the ‘Propeller’. Retaining the visibility of this feature shows a well-balanced image. Wide-field shots taken at longer exposures to record the cluster’s outer stars may also reveal a nearby 16th-magnitude galaxy known as PGC 2085077. If it proves elusive, there is another galactic treat slightly farther out in the form of NGC 6207 which, at mag. +12.1, is much easier to pick up. With so much on offer, M13 is a fantastic astrophotography target; one well suited for imaging whether you’re a beginner or at a more advanced level.

Key technique PERFECTING THAT NATURAL LOOK

Combining astro images taken at different exposures to create a high dynamic range shot is suitable for any object that has a bright core surrounded by faint detail – it works just as well for nebulae and galaxies as it does for globular clusters like M13. The biggest skill challenge, as is ever the case when it comes to image processing, is to try and keep the object looking natural. You will likely need to use the Curves adjustment tool to merge your two exposures and it’s here subjectivity can creep into the equation. Just make sure you don’t overdo it!

 Send your image to: [email protected]

STEP 5 Use the selection polygon tool to draw an area around the overexposed core in the longer exposure. This selection should be slightly larger than the burnt out inner core region. Copy the region to the clipboard and create a layer mask from it; in Photoshop this entails holding down the Alt key and clicking the layer mask button, circled.

STEP 6 The properly exposed inner core should become visible through the hole created by the layer mask. Click on the layer mask icon in the layers display and apply a fairly extreme Gaussian blur so that its edges stop being noticeable and disappear. Make sure the Propeller remains visible in the core. Flatten and save to create a final image.

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In this image of Cygnus-X, the yellow-white areas are centres of star formation, while clouds of dust show up green and red

THE LIFE

OF STARS

F

or thousands of years, humanity has been staring at the night sky, wondering what was up there and where it came from. Much effort has gone into studying the stars and we now understand them fairly well. We know that stars are the chemical factories of the Universe, forming the heavy elements we see around us – both during their lives and in their death throes. As our understanding of the lives of stars increased, astronomers began to understand that not only did stars die, but the biggest, brightest ones did not live very long at all. By the mid‑20th century, it became apparent that some clusters of very bright stars should have dispersed after a few tens of millions of years and therefore must be relative newcomers. Astronomers realised that this meant there must still be stars forming in our Galaxy today and that they weren’t just a static backdrop. But how and where did they form. A key development in understanding star birth was the discovery of interstellar material – the stuff that lies between the stars. These clouds of dust can be seen as dark silhouettes against the background starlight, particularly when looking through the disc of our Galaxy, the Milky Way. These dust clouds have been observed for millennia, but with the advent of radio astronomy it became apparent that there were also vast quantities >

NASA/ESA AND THE HUBBLE HERITAGE (STSCI/AURA)-ESA/HUBBLE COLLABORATION, THINKSTOCK, NASA/JPL-CALTECH/HARVARD-SMITHSONIAN CFA

Chris North explores the wonder of star formation and explains how the Herschel Space Observatory has expanded our knowledge of this mysterious process

THE LIFE

NASA/ESA AND THE HUBBLE HERITAGE (STSCI/AURA)-ESA/HUBBLE COLLABORATION, THINKSTOCK, NASA/ESA/M.LIVIO AND THE HUBBLE 20TH ANNIVERSARY TEAM (STSCI), NASA/ESA/JPL-CALTECH/IRAM, ESA, NASA/JPL-CALTECH/R. HURT (SSC/CALTECH)

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> of previously unseen gas between the stars, most of which is in the form of hydrogen. This interstellar material has roughly the same composition as the stars themselves and so provides a huge reservoir of material from which stars can form. However, working out the details of how these tenuous wisps became massive stars required a better understanding of what was going on within the clouds of dust.

In the infrared

a pillar of dust and gas in the Eta Carina Nebula, home to many young stars

active regions within and provides few clues as to what’s going on inside. The advent of infrared astronomy, which enabled astronomers to study the dust itself and the processes occurring inside it, opened up the whole new research field of observing star formation. The first infrared telescopes looked at the shorter wavelengths, called nearinfrared, and only saw the warmest dust that is typically very close to stars that have already formed. But towards the end of the 20th century the technology behind infrared detectors developed in leaps and bounds, allowing astronomers to start observing longer wavelengths in the mid- and even far-infrared. These are wavelengths up 1,000 times longer than visible light, so much colder material could be seen.

“We now have a fairly good idea of how stars form, though the devil is in the detail”

Unfortunately, these all-important regions are blocked from view in visible light by the clouds of dust that surround them and those clouds are only seen in silhouette. Some of the clouds appear to shine in visible light, forming bright nebulae in the sky, but that is just the glow of hot, energised gas on the margins of skyatnightmagazine.com 2013

Þ This Hubble image shows

OF STARS AN INFRARED EYE Until its coolant ran out in March 2013, the Herschel Space Observatory was the most advanced infrared space telescope ever launched, thanks to its large, 3.5m-diameter mirror and advanced scientific instruments. Rather than stars, Herschel saw the gas and dust between the stars. This interstellar material can cool to temperatures as low as –260°C, where it is only visible in the long infrared wavelengths of light that Herschel’s instruments saw. Over its mission lifetime Herschel has shown us cold clumps of gas and dust in the process of forming new stars, the structure of dust in the spiral arms of nearby galaxies and the history of star formation throughout the Universe. To do this the instruments onboard Herschel had to be kept very cool, at just 0.3°C above absolute zero, or a chilly –273°C. Left to its own devices, the spacecraft only cooled to around –200°C, which was not nearly cold enough. A large black tank of liquid helium helped cool the instruments to their required temperatures, but in doing so the liquefied gas slowly boiled off into space. After four years in space, that helium has now run out, and Herschel’s instruments have warmed up and stopped working. But the data and images they have sent back will provide a huge archive for astronomers to analyse – work that will continue for years and decades to come.

Despite these technological milestones, there were a number of obstacles that were either difficult or expensive (or both) to overcome. Firstly, most of the detectors need to be very cold in order to operate and so require sophisticated cooling technology. Secondly, Earth’s atmosphere absorbs much of the infrared light we might like to observe and even emits its own. As a result, most mid- and far-infrared telescopes are positioned above Earth’s atmosphere, or at least above most of it. They can be flown onboard aeroplanes, dangled from high-altitude balloons or, as was the case with the Herschel Space Observatory, launched on a satellite. Advances in both satellite and rocket technology have meant that over time, the missions have become both larger and more complex – culminating thus far in Herschel, which provides the ability to see much fainter objects at higher resolution.

þ An artist’s impression of a young star surrounded by a protoplanetary disc

fragments, so a cluster of cold, dusty cores forms. The centre of each core will gradually increase in temperature and density, eventually reaching the conditions necessary for nuclear fusion to begin. At this point, a star is born. Typically, only about a tenth of the material in a gas cloud forms stars, so the newborn ‘protostars’ are embedded in cocoons of gas and dust. As they fire up their nuclear cores, these infant stars begin producing heat and light. Initially they burn very hot and very bright, and the intense visible and >

A star is born After a few decades of serious infrared astronomy, we now have a fairly good idea of how stars form, though as ever the devil is in the detail. It all starts with a cloud of gas and dust, drifting through the Galaxy. Typically, these clouds contain enough material to create a few hundred or a thousand stars, though some are much more massive. Initially, the pressure of the gas itself is sufficient to prevent the cloud collapsing under gravity and the cloud either continues to grow or just sits there drifting between the stars. Unless they’re being heated by a nearby star, these clouds cool and shrink into clumps. The clumps then break into skyatnightmagazine.com 2013

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THE LIFE

NASA/ESA AND THE HUBBLE HERITAGE (STSCI/AURA)-ESA/HUBBLE COLLABORATION, THINKSTOCK, ESO/Y. BELETSKY, ESO/P.CROWTHER/ C.J.EVANS, ESO/J. EMERSON/VISTA, ROB GENDLER/WWW.ROBGENDLERASTROPICS.COM, ESA/PACS/SPIRE/HOBYS CONSORTIA

The Jewel Box cluster, a young star grouping that will eventually disperse > ultraviolet light is enough to push away the surrounding gas and dust. What’s left at the end is a cluster of hot, bright, young stars blowing a cavity in their surroundings. A great example of this is the Eagle Nebula, at the centre of which is a cluster of a few hundred stars that formed a few million years ago. The light from these stars is eroding away the surrounding regions, leaving natural sculptures such as the famous ‘Pillars of Creation’. Although most stars form in groups of various sizes, it is rare for them to stay together indefinitely. Some will be captured by each other’s gravity, forming pairs, triplets, or even larger groupings, but most of the stars will drift away from each other over a few hundred million years.

Massive dilemma The brightest stars in a cluster are the most massive, but these are just the tip of the iceberg. For every star that is 10 times the mass of the Sun, there are hundreds of Sunlike stars, and even more that are smaller still. The current record for the most massive star is held by the unimaginatively named R136a1 in the Large Magellanic Cloud, which is almost 300 times as massive as the Sun. Although they are very rare, these massive stars have a huge impact on their environment. They burn incredibly brightly, at millions of times the luminosity of the Sun, creating skyatnightmagazine.com 2013

enormous bubbles in space. With much hotter, denser cores, they also form much heavier elements than lighter stars such as the Sun and end their lives in much more violent explosions. The powerful shockwaves these create distribute their material much further afield. Despite the significance of these massive stars, theories of star formation have generally struggled to explain how they can grow so large – their intense glow should have blown away the surrounding gas and dust long before they became so massive. Part of the reason for the puzzle over their formation is that these stars are incredibly rare and so it is hard to collect observational data about them. To see massive stars in their infancy, or even before they have fully formed, we need to stare deep within the dusty cocoons surrounding them. Some have postulated that these massive stars form from the merging of smaller stars, but recently the favoured theory has been that their formation is caused by the presence of other stars – a scenario called ‘triggered star formation’. Here the compression of gas and dust by the radiation from a pre-existing star, or cluster of stars, aids the formation of a new generation, often allowing them to grow more massive than they would otherwise.

“Although most stars form in groups, it is rare for them to stay together indefinitely” þ The centre of cluster R136

in the Large Magellanic Cloud is home to the most massive star yet detected

There are numerous examples of this triggered star formation in the catalogue of objects studied by Herschel. The region RCW 120, towards the constellation of Scorpius, is a 10-lightyear-wide bubble being blown in space by a star at its centre. Although the star itself is unseen by Herschel, the telescope can see a bright blob on the edge of the bubble – a dense clump of gas and dust with a protostar at its heart. That protostar is already around ten times the mass of the Sun, and is surrounded by enough gas and dust to make a thousand Suns. The bright light from the central star has not managed to blow this material away because the gas and dust is pushing against the bubble. The protostar’s formation is therefore only made possible by the presence of the bubble, making this the first confirmed observation of triggered star formation. By looking at much larger regions, including great swathes of the plane of our

OF STARS PEERING THROUGH THE DARKNESS In 1800, Sir William Herschel discovered light beyond the red end of the visible spectrum – light that we now call infrared. More than 200 years later, his namesake is the latest space telescope to have explored the Universe in infrared light. The longest wavelengths of infrared light are called far-infrared, with wavelengths hundreds of times longer than those of visible light. As well as stars, space is threaded with gas and dust, forming clouds and filaments that, in visible light, are silhouetted against the background starlight. But in infrared light these clouds of gas and dust are seen to glow with their own light. Using infrared telescopes, we can study the density and temperature of the dust, picking out the locations where stars are currently in the process of forming. The final, critical stages of star birth involve the coldest clumps of dust and therefore the longest wavelengths of infrared light. This makes Herschel’s instruments ideal for studying them.

Þ Two different shots of the Orion Nebula, M42. Note how the infrared image, left, shows up regions of star formation that are hidden by dust clouds in visible light, right own Galaxy, Herschel has allowed astronomers to look at where different types of stars form. The images have revealed the structure of interstellar dust in more detail than ever before, confirming that it forms filaments that thread between the stars, stretching over many lightyears. Over time, knots and clumps form along the filaments and it’s these that collapse under gravity to form small groups of stars. Where two or more filaments intersect, larger clumps are formed, leading to the formation of larger star clusters. The most massive stars in these clusters will live fast and die young, generating shockwaves upon their death that create a new network of filaments, thus restarting the stellar life cycle.

Mysteries remain While our picture of star birth is constantly improving, thanks in recent years largely to Herschel, there are still many questions that remain. For example, we don’t know for sure the exact processes that lead to the formation of the filaments mentioned earlier. And with so few examples to study, the formation of the most massive stars is still very much a matter of debate. Astronomers will continue to use data from space telescopes like Herschel to answer these questions, but there can be no doubt that any new information gleaned will raise a great many more. S ABOUT THE WRITER

Þ RCW 120 is a vast bubble being blown in space by a central star. On the bubble’s bottom fringes, a protostar is forming – an example of triggered star formation

Based at the University of Cardiff, Dr Chris North is an astronomer working with the Herschel Space Observatory. He is also a reporter for The Sky at Night.

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THE LIFE

STAR DEATH Zach Cano explains how we are uncovering the inner workings of supernovae, the incredibly powerful explosions at the end of stars’ lifetimes

Cassiopeia A is the remnant of a supernova explosion whose light first reached Earth 300 years ago

OF STARS

The story so far Despite the abundance of observations, there are still fundamental questions about what happens within a supernova, which supercomputer simulations are bringing us closer to answering. This much we do know: supernovae occur when certain stars explode violently, in the process ejecting a large amount of material into space in a brilliant and energetic display. Supernovae are classified into two types, depending on whether hydrogen can be detected in their spectrum: Type I has hydrogen, Type II does not. There’s another level of classification for Type I outbursts – into Type Ia, Ib and Ic – that’s applied by analysing the spectrum further. Type Ia >

NASA/ESA AND THE HUBBLE HERITAGE (STSCI/AURA)-ESA/HUBBLE COLLABORATION, THINKSTOCK, X-RAY: NASA/ CXC/SAO; OPTICAL: NASA/STSCI; INFRARED: NASA/JPL-CALTECH/STEWARD/O.KRAUSE ET AL.

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he end of a star’s life is a dramatic event. Stars like our Sun expand to become red giants and then blow their outer shells into space to create a planetary nebula. But there are others that go out with a bang, ending their lives in a supernova. Among the most powerful and brightest explosions in the Universe, these events can outshine even the host galaxy in which they occur. Their mysterious and spectacular appearance has fascinated humankind for centuries – the first recorded example was documented by ancient Chinese astronomers in 185AD. In subsequent centuries, astronomers could only record very luminous events that were visible to the naked eye: up to the 20th century, only seven supernovae were recorded. But in the past 113 years, 6,242 supernovae have been documented, and the vast majority (85 per cent) of these were recorded in the past 20 years, the total swelling as ever fainter events have been picked up – both by amateur astronomers and in automatic searches by professional telescopes.

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NASA/ESA AND THE HUBBLE HERITAGE (STSCI/AURA)-ESA/HUBBLE COLLABORATION, FRANK ZULLO/SCIENCE PHOTO LIBRARY, THINKSTOCK X 7, NASA/CXC/M.WEISS X 2

star’s nuclear fuel is exhausted, while the hydrogen layer still surrounds the star. Without the energy produced by consuming its fuel, the star is no longer able to counterbalance the force of gravity, and so it collapses under its own weight, eventually leading to a gargantuan explosion. Throughout its life, a star’s energy source arises from nuclear fusion. When a star is born, it is made mostly of hydrogen. In the stellar core, the temperature and pressure is so high that hydrogen fuses to form helium, as well as releasing a large amount of energy. The rate at which the hydrogen fuel is consumed depends on how massive the star is – very massive stars will burn through their nuclear fuel in a few million years, while smaller stars can take over 10 billion years.

The beginning of the end Þ An Anasazi Indian

petroglyph at Penasco Blanco in New Mexico, of a supernova observed in 1054. We see the remains of this supernova today as the Crab Nebula, inset

> supernovae are thought to occur in two rather

spectacular ways. The first scenario is when a white dwarf star in a binary system explodes after reaching a critical mass limit by pulling in too much material from its companion star. The second is when two white dwarf stars violently merge. These are also called thermonuclear supernovae. In terms of what we think causes them, Type Ib and Ic supernovae are closer to Type II supernovae than Type Ia. The former three are all thought to occur when a massive star comes to the end of its life and explodes violently, its core collapsing. In Types Ib and Ic, the core is thought to collapse after the star has burnt off its outer layer of hydrogen. In a Type II supernova, the core collapses when the

Once the hydrogen in the core has been exhausted, nuclear reactions cease. Throughout the star’s life, the only force that has stopped the star from collapsing under gravity has been the counter-balancing energy produced through nuclear fusion. When the hydrogen runs out, the star’s core contracts under the influence of gravity until the temperatures and pressures are so great that helium is fused into carbon. It is here that a star’s mass comes into play. For a star of relatively modest mass such as our own Sun, the contraction of the core will also cause the outer layers to expand and the star will enter a red giant phase. Eventually the helium will be entirely burned into carbon, resulting in a carbon core surrounded by an envelope of material that the star has blown off into space. The carbon core is known as a white

CORE-COLLAPSE SUPERNOVA Stars that are more than eight times the mass of the Sun live short, bright lives – only a few million years, compared to the expected 10-billion-year lifespan of the smaller Sun. When it is born, a massive star burns hydrogen in its core, where the temperatures and pressures are so high that the hydrogen is fused into helium. The massive star then burns heavier and heavier elements in its core, from

Protostar

Blue main sequence star

skyatnightmagazine.com 2013

Red supergiant

hydrogen to helium to carbon – all the way up to iron. Once a particular fuel has been consumed, the core contracts until it is hot and dense enough to burn the next heaviest element, while a shell of material forms around it. Over time, the star develops an onion-like structure. Eventually, when the star’s core is made up of iron and other heavier elements that can’t be burnt, the nuclear reactions within the star

Helium burning supergiant

cease. At this point, there’s no more pressure holding off the gravity of the outer layers, which subsequently begin to implode. Once this happens, the pressures in the core become so high that protons and electrons combine to form neutrons, and a neutron star is created. The remainder of the imploding material rebounds off this neutron star in the form of a catastrophic supernova explosion.

Neutron star or black hole Multiple shell burning supergiant

Supernova

Þ The life cycle of a star more than eight times the mass of the Sun, ending in a supernova that leaves a neutron star or a black hole behind

skyatnightmagazine.com 2013

OF STARS THERMONUCLEAR SUPERNOVA There are two possible triggers for a Type Ia supernova, both of which involve a binary star system. In the first scenario it is thought that a white dwarf slowly draws material from a larger companion star. Eventually the white dwarf accretes so much material, and its mass grows so large, that it starts burning

carbon in its core. From this carbon burning grow the seeds of the star’s eventual demise. Eventually a thermonuclear explosion leads to the total destruction of the star and the expulsion of its ashes into space. The second scenario thought to be behind Type Ia supernovae is when two white dwarf

Þ Type Ia supernovae occur when a star accretes matter from its binary partner… dwarf star, while the glowing shell of gas that surrounds it is called a planetary nebula. But in more massive stars the cycle of fusion continues, burning heavier and heavier elements until it forms an iron core with shells of different elements surrounding it like the layers of an onion. Once the iron core is formed, nuclear fusion ceases and the core contracts irrevocably. The collapse occurs very rapidly and so forcefully that electrons are smashed into protons to form neutrons, ultimately leading to the formation of an incredibly dense ball of neutrons known as a neutron star. The formation of the neutron star halts the core collapse, and the layers that once surrounded the core slam into it. The collision creates a shockwave that rebounds through the star and ejects the stellar material out into space. The trigger for a Type Ia supernova is also thought to be carbon burning within the star’s core, but it comes about in a different way. Here one model has a white dwarf star’s carbon core

stars merge. Here, stars that once existed in a binary system gradually twirl together over time until they collide violently. In this scenario, the accretion of material is thought to happen very rapidly, but the outcome is the same – the total obliteration of both stars, with their remains scattered into space.

Þ …or when the two stars collide

reigniting after it accretes material from its companion star in a binary system, eventually triggering a thermonuclear explosion. It is the consistency of this explosion’s light curve that makes Type Ia supernovae useful in measuring distances to their host galaxies. The second model for Type Ia’s also involves a binary system of two white dwarfs. Here the supernova is triggered when the stars violently collide and merge together.

Unanswered questions These current models may give the impression that astronomers have this area sewn up, but fundamental questions still remain. During a core-collapse supernova, quite how the shockwave ejects material from the star into space is a matter of debate, and it’s unclear what initially triggers the thermonuclear explosion of a Type Ia supernovae. While some astronomers are building bigger and more powerful telescopes to study supernovae, others are set on recreating them in a lab using > skyatnightmagazine.com 2013

THE LIFE

36 72

NASA/ESA AND THE HUBBLE HERITAGE (STSCI/AURA)-ESA/HUBBLE COLLABORATION, IMAGES COURTESY OF ARGONNE NATIONAL LABORATORY/S.COUCH, STAN WOOSLEY, LEONHARD SCHECK/SCIENCE PHOTO LIBRARY, ESO

models of the explosion that were spherically symmetric. In the 1990s, advances in numerical codes meant that it was possible to include two spatial dimensions, and more sophisticated models meant that scientists could simulate the elements of a star in motion during the explosions – so-called hydrodynamical mixing. This led to new insights. Core-collapse models showed that acoustic vibrations within the star, reinforced by turbulent mixing in the material flowing out, could play a key role in adding energy to the shockwave at vital moments. Another factor highlighted by these simulations was the energy contained in the huge outflow of neutrinos (energetic subatomic particles) created during the core collapse as electrons and protons are forced together. At the same time, improved computer technology allowed more and more physical processes to be included in the simulations. Teams of astronomers were finally able to use the world’s fastest supercomputers to run their simulations and model the explosions in ever more realistic conditions.

Þ A simulated supernova,

300 milliseconds after core collapse; the turbulence is caused by unseen neutrinos

Modelling supernovae > advanced computer simulations. The only

problem is that, after more than 50 years of trying, no-one has been able to successfully recreate a supernova in a simulation. From the 1960s to the 1980s, the computer simulations that could be carried out were very basic. Due to the limitations in available technology, many assumptions had to be made. Simulations were run in only a single dimension and, for reasons of simplicity, astronomers were limited to geometric

One such group has been led by theoretical astrophysicists Dr Hans-Thomas Janka at the Max Planck Institute for Astrophysics in Germany. They used a series of supercomputers in one of the first successful simulations of a core-collapse supernova. By working advanced models of the outflow of neutrinos from the stellar core into their two-dimensional simulations, they reproduced how the neutrinos interacted with matter within a dying star. The results supported theories that the

SUPERNOVA SIMULATORS

Þ Mira’s 3D simulation of a core-collapse supernova; the ‘bubble’ is the shock wave

skyatnightmagazine.com 2013

The computer simulations being used by astrophysicists today are vastly superior to those used only a decade ago. The greatest computational challenge is the successful reproduction of a supernova – a challenge that has not been adequately overcome in over 50 years of attempts. One of the key challenges is including very complicated yet fundamental physics in the simulations to make them as real as possible. Today, simulations need to reproduce the explosion in three dimensions, as well as accurately model the complex behaviour of the material in the explosion. To do this, simulations have to recreate dynamic movement within the star with hydrodynamical codes, as well as accurately describe the way neutrinos are generated during the explosion. This is the challenge for today’s nextgeneration supercomputers; machines like Mira at the Argonne National Laboratory

in the US, which can operate at 10 petaflops – meaning it can carry out 10 quadrillion (10 million billion) operations a second, and has 768 terabytes of memory. In comparison, the average desktop computer operates at a few gigaflops (handling a few billion operations a second), and may have only 6-8GB of memory.

Þ The Mira supercomputer, built by IBM and housed at the Argonne National Laboratory

OF STARS THE EXPERT Dr Stan Woosley, professor of astronomy and astrophysics at the University of California, Santa Cruz, uses computer simulations to simulate the deaths of massive stars What have been the key developments in simulating corecollapse supernovae over the past decade? I believe that it is a growing realisation that magnetic fields and rotation must be important in the deaths of some massive stars, which is based upon the connection of supernovae with gammaray bursts. Also key has been developing computer codes of increased realism and complexity to run on the exponentially advancing computer technology.

Why is it so difficult to explode a massive star in a simulation? The difficulty is that the simulations are very complex and the explosion itself is only a small fraction – about a thousandth – of the total energy being tracked. It is also hard because it is necessary to model the explosion in three dimensions and include many different aspects of fundamental physics including general relativity, rotation, and complicated equations of state. What does the future hold for our ability to simulate supernovae? In general I am optimistic about the future. The good news is that we’ve most likely

explosions of stars with 11 to 15 times the mass of the Sun receive a crucial boost in energy through hydrodynamic instabilities: the star’s layers were being heated, by neutrinos, into a bubbling mix. Similar developments have been made in simulations of Type Ia supernovae. A team of astrophysicists in the US has successfully modelled the stages before a thermonuclear explosion in the first three-dimensional simulation to incorporate complex hydrodynamics. Their results not only confirmed the results of earlier, less sophisticated attempts, but also revealed that the behaviour inside the white dwarf just before detonation is more complex than expected. The lead author of the study, Dr Michael Zingale of Stony Brook University, explains: “We focused on the early stages of the Type Ia explosion, trying to understand how the convective stage preceding the explosion ignites the initial burning front. Our results indicate that the ignition of the burning front is likely off-centre, which may lead to asymmetric explosions.” Dr Zingale’s simulations were performed on the supercomputers at the National Energy Research Scientific Computing Center in Oakland, California. Despite their huge power, each simulation still took over a million hours of processing time to complete. Research and simulations into supernovae are still ongoing. “We will need a couple of years before we solve the problem of supernova explosions,” says Dr Janke. Modelling a supernova is a grand computational challenge requiring very complicated simulations that incorporate many aspects of fundamental physics. With current technology, a single simulation that includes all three spatial dimensions and all of the key physical principles

pinned down the important basic physics, while computers and our codes are becoming equal to the challenge, and progress is being made. The calculations being done today could only have been dreamed about 10 years ago. More problematic are the codes needed to use those machines effectively. Certainly people are making advances, but no-one has yet produced a simulation that includes all of the necessary physics. They will, though. The real challenge may not be in just getting the right answer, but in convincing the community of people working on the problem that the answer, once it’s been found, is indeed correct and robust.

can take several weeks to run on a supercomputer; on a normal desktop computer they would take literally thousands of years to complete. Adding even greater optimism are developments in observing technology. When future supernovae occur, astronomers will be able to observe them at all wavelengths, as well as any change in neutrinos and maybe even gravitational waves. These observations will help us to further uncover the mechanisms and the structure of these enigmatic exploding stars. S

Þ SN 1987A was visible to the naked eye. When future supernovae occur, astronomers will be able to study them in greater detail than ever before

ABOUT THE WRITER Zach Cano is a post-doctoral research fellow investigating core-collapse supernovae and gamma-ray bursts at the University of Iceland’s Centre for Astrophysics and Cosmology.

skyatnightmagazine.com 2013

The glow

space FROM THE EDGE OF

PEKKA PARVIAINEN/SCIENCE PHOTO LIBRARY

The dark winter nights may be gone, but noctilucent clouds offer a visual treat for summer observers, says Tom McEwan

NLCs shine a distinctive blue against the dark twilight of a late evening in summer

A

s spring starts to give way to summer, observing the night skies becomes increasingly challenging as the hours of available darkness get shorter. From late May onwards, for instance, astronomers based in central Scotland experience twilight conditions throughout the night, and night-time skies continue to brighten as the solstice arrives on 21 June. Understandably, many of us – but especially those located at more northerly latitudes – regard this period as a summer shutdown and look forward to the return of genuinely dark skies

in early August. However, there is an intriguing and unusual observing target that is only visible in summer’s twilit skies – noctilucent clouds. Noctilucent clouds, more commonly referred to by the abbreviation NLCs, were only discovered in 1885, following the 1883 Krakatoa eruption. The massive explosion of this Indonesian volcano had an impact all over the world, generating eye-catching sunsets and leading to an increased awareness of related atmospheric phenomena. NLCs are located in the upper fringes of Earth’s atmosphere and are therefore a quite distinct and separate cloud type from the familiar weather or ‘tropospheric’ clouds of the lower atmosphere. More precisely, they form in the mesosphere, just below

the mesopause (the coldest part of the atmosphere), in a thin sheet at an average height of around 82km. Indeed, NLCs are found close to the edge of space, a fact impressively illustrated by photographs taken from the International Space Station (see overleaf) that show a thin line of NLCs in dark space, high above the Earth’s limb.

In the clouds The precise nature of these clouds is not yet fully understood, but they are thought to form when water vapour condenses onto minute atmospheric particles and freezes. The most likely sources of such particles would be meteor debris (meteors can vaporise at around 100km, above the NLC layer) or volcanic activity. Studies indicate that NLCs need extremely cold >

76

> temperatures, close to around –120 º C, to

form. Contrary to what may be expected, temperatures in the mesosphere are at their coolest over the summer, which explains why NLCs have such seasonal behaviour. Even when they’re at their most visible, the composition of NLCs is extremely tenuous. They only become visible against a twilight sky when the Sun lies between 6º and 16º below the horizon. Any less than 6° below the horizon and the Sun’s illumination of the background sky is too bright, swamping the fainter light of NLCs; on the other hand, if the Sun

Þ NLCs as seen from

the International Space Station in July 2012

PHOTO TIPS CAMERA Most compact or DSLR cameras are capable of capturing NLCs.

NASA, CANON, THINKSTOCK X 3, TOM MCEWAN X 3

TRIPOD NLCs are comparatively faint, so cameras will need to be mounted on a tripod with a remote shutter release cable attached. LENS The field of view of a standard-sized lens is usually sufficient, but extensive displays will require wide-angle or even fisheye lenses to capture them in full. EXPOSURE Accurate exposure guides are difficult to provide as the brightness of the twilight sky and NLCs is so variable. However, using a fully opened lens

skyatnightmagazine.com 2013

and ISO setting of 200-400, an exposure of 4-6 seconds would be a good starting point. Review your test image to see if you need to make the exposure longer or shorter. MOVIE An alternative photographic technique, commonly used when recording a series of images at regular intervals, is to set the camera to shutter priority. This fixes the exposure duration but allows the camera to assign the correct aperture value. Once a series of images has been recorded like this, they can be compiled into a movie. Replaying this will speed up the movement of the field, revealing changes in NLCs that the human eye is otherwise unable to follow in real time.

is more than 16º below the horizon, then the NLC sheet lies in the Earth’s shadow, becoming invisible. This ‘Sun-Earth-Observer’ geometry imposes geographic restrictions on NLC visibility, as does the physical location of the NLC sheet itself, which is generally located from 60° to 80 º latitude in each hemisphere. This explains why the bulk of NLC sightings are made from within the latitude band of 50° to 60 º, which conveniently encompasses the UK and Ireland. Nonetheless, NLCs can be, and are, observed from outside this area. Rare, isolated sightings have been made from as far south as 40 º latitude, both from Europe and the US.

When to observe Each year, NLCs become visible in a fairly predictable pattern. The earliest sightings usually come near the end of May or early June, when cooling of the mesosphere sets in. Early sightings are normally of weak, simple formations, but as the season progresses displays tend to be brighter, more complex, endure for longer and occupy larger areas of sky. Records show a clear peak in activity from around mid-June through to mid-July, by which time the season starts to gradually tail off. By early August the season is all but over, though rare sightings have been made later in that month. NLC frequency also varies from year to year, and there is some evidence to suggest that this is influenced by the solar cycle. NLC incidence is generally higher over the few years of solar minima, while it drops at solar maxima. The NLC season of 2009 is a case in point: NLC incidence was unusually high and this coincided with very low solar and auroral activity. It has been suggested that auroral heating of the upper atmosphere could perhaps account for this variability. However, NLC >

NOCTILUCENT CLOUDS MAY 77

CLOUD REPORT Amateur observations of NLCs are of great value to professional scientists and you only need a pen and paper to make them. Record the date, time and location from which the observations were made, and take note of the NLCs’ angular height above the horizon and its extent across the sky in azimuth, using an

outstretched hand is roughly equal to 20º. Also record the structures present in the clouds and estimate the brightness. Aim to record these details every 15 minutes – on the hour, at quarter past and so on. It’s also worth recording the absence of NLCs when skies are clear and the Sun is the requisite 6º-16º below the horizon.

NLC STRUCTURES

 Type I: Veil This type of NLCs appear as a patchy, fibrous sheet with little or no obvious structure, sometimes visible in the background of other forms. It can look like a glowing fog or mist.

▲ Type II: Bands These NLCs feature horizontal lines or streaks that can be sharp (Type IIa) or diffuse (Type IIb). The bands may be parallel, or meet and cross.

Com p le x s st ru c tu re

can’t be classified Often an NLC display is when four as only one type, which in useful. e com s ion extra classificat clumps. Type S - Bright knots or g a band. ssin cro s ow Bill P e Typ ven structure. Type V - Net-like, interwo any form that for k bac fall A – O e Typ . Written does not fit in Type I-IV of this type ges ima and s tion crip des define it. her furt are ver y useful to

▲ Type III: Billows A distinctive structure of rippled or wavy bands, Type III NLCs are often compared to the sand patterns formed on a beach at low tide.

NLC b ri g h t n e s s

The brightness of an NLC display ca n be measured again st a five-level sca le. 1. Weak, barely visible. 2. Clearly detected , low brightness. 3. Clearly visible, high contrast with twilight sky. 4. Very bright, co nspicuous to casu al observers. 5. Extremely brigh t, able to illumina te objects facing dis play.

▲ Type IV: Whirls Looped, curved or twisted forms. Small whirls can be classed as Type IVa, medium size as IVb and large scale loops as IVc.

skyatnightmagazine.com 2013

Exosphere

78 NOCTILUCENT CLOUDS MAY

WHY DO WE SEE NLCS?

600km ISS (400km)

180km

UK observers can see NLCs due to a bit of fortunate geometry. When the Sun is between 6º and 16º below the horizon, its light will hit any NLCs present in the mesosphere, making them visible from Earth at latitudes of around 60º to 80º. Beyond this range, NLCs appear much less frequently.

Sunlight path

Thermosphere

NLC visible due to reflection of sunlight

160km

140km

Aurorae

120km

100km

Tropospheric clouds in shadow

PEKKA PARVIAINEN/SCIENCE PHOTO LIBRARY

Sun at 6º below the horizon

> and aurora have been observed in the same sky so this relationship, if it exists at all, is clearly not a straightforward one. During the NLC season a display can appear at any time of night, but will not be visible on every night. If present, it can last for only a few minutes or be visible all night. A typical display will commence about an hour or so after sunset, initially appearing as faint, wispy streaks, perhaps extending only a few degrees above the horizon. As the night unfolds and the twilight sky darkens, the NLCs become more obvious and may rise higher in the sky, often developing more intricate structure and becoming noticeably brighter. As local midnight nears, NLCs may fade somewhat and shrink in size as the solar illumination becomes less favourable. But after midnight, this pattern of behaviour is reversed: NLCs get brighter and stronger again until they are swamped by the brightening sky, perhaps an hour or so before dawn.

Clouding the issue NLCs can, on occasion, be easily misidentified. The key thing to remember is that weather clouds generally appear dark, silhouetted against the twilight, whereas NLCs will always appear brighter than the background sky, often exhibiting a signature bluish tone. Nonetheless, thin streaks of cirrus cloud, especially if illuminated by moonlight, skyatnightmagazine.com 2013

Þ Once seen, these

beautiful twilight displays at the edge of space will never be forgotten

80km Meteors 60km

40km Weather balloon Weather clouds

Troposphere

Observer

Stratosphere

Mesosphere

NLCs

20km

0km

can bear a striking resemblance to NLCs, and low bands of horizon haze can also create false impressions of Type II NLC bands (see page 77). A good test to perform on any suspected NLCs is to examine the feature with binoculars. Tropospheric clouds tend to remain diffuse and blurred when magnified, while NLCs almost always reveal finer detail. When it comes to NLCs, there are still many questions left to be answered. Amateur astronomers have played, and continue to play, an important role in gathering observational data and contributing to the ongoing investigation and research into how displays are caused. So if you see NLCs in the UK this summer, note down the details of your sighting and email a report in to the Aurora Section of the British Astronomical Association at www.britastro.org/aurora, where it will be collected, collated and archived. Reports can also be submitted online to the Noctilucent Cloud Observers’ Homepage at www.nlcnet.co.uk. S ABOUT THE WRITER Tom McEwan has been observing NLCs for over 25 years, and in 1995 founded the NLC Observers’ Homepage – the first website dedicated to these phenomena.

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BIG IDEAS

TO EXPLAIN LIFE, THE UNIVERSE AND EVERYTHING

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AVAILABLE NOW - ONLY £8.99 PLUS P&P

www.buysubscriptions.com/20bigideas Or call: 0844 844 0254† and quote BIGSK13 Postage prices are as follows: £2.00 (UK), £4.60 (Europe), £4.80 (Rest of the world). All orders are subject to availability. Please allow 28 days for delivery. † Calls to this number from a BT landline will cost no more than 5p per minute. Calls from mobiles and other providers may vary.

80

Skills

Brush up your practical astronomy prowess with our team of experts

Contents The guide

How to

Sketching

Scope doctor Lost in space

80

82

85

86

Explore the electromagnetic spectrum in full

SKILLS

Observe the Sun safely and build a white light filter

Learn how to draw the Splinter Galaxy

Steve Richards answers your astro equipment queries

87

Keith comes to terms with his inability to catch comets

The guide

The electromagnetic spectrum With Olivia Johnson

There’s far more to astronomy than what the human eye can reveal VISIBLE LIGHT

RADIO

MICROWAVES

INFRARED

ULTRAVIOLET

X-RAYS

GAMMA RAYS

CHANDRA KEPLER PLANCK

HUBBLE SPITZER

FERMI

The spectrum in full: beyond the visible, a fleet of space probes – a feted few of which are shown above – are scouring the skies in most wavelengths

S

targazing far from city lights, you may be amazed by how much more you can see in a truly dark night sky. Or you might be dazzled by the clear, colourful views of space talented astrophotographers produce using sophisticated cameras and techniques. But even in the darkest conditions and using the best equipment, you won’t see the majority of light shining towards Earth.

skyatnightmagazine.com 2013

The rainbow of visible light we’re able to see makes up a tiny slice of a much broader continuum called the electromagnetic spectrum. Though you can’t see the rest, you’re probably familiar with many of them. Beyond the red end of the visible spectrum is the infrared light detected by night-vision cameras, the microwaves you use to heat your dinner and the radio waves used in media broadcasts. At the

other end is the ultraviolet light that causes sunburn, the X-rays used in medical imaging and the gamma rays used in some cancer therapies. All except gamma rays are subdivided further, into smaller slices of the continuum. All kinds of light are electromagnetic radiation, a form of energy made up of oscillating magnetic and electric fields, which spread like a wave. The length

SKILLS MAY 81

VISIBLE

of the wave determines the type of light, how energetic it is and how it interacts with matter. Visible wavelengths are measured in nanometres (nm), a unit of length equal to one billionth of a metre. The human eye can detect red light from about 700nm down to violet light at about 400nm, a very small section. At the extremes, the lowest-energy radio waves have wavelengths measuring thousands of kilometres, while the most energetic gamma rays have wavelengths that are smaller than an atom at a few trillionths of a metre.

FAR INFRARED AND X-RAY

The invisible cosmos The structure and extent of the Eagle Nebula, M16, appears quite different in non-visible light VISIBLE (HUBBLE PALETTE)

NEAR INFRARED

MID INFRARED

light, causing them to appear opaque, but in infrared light these stellar nurseries are near transparent, revealing the young stars forming within. On a larger scale, we can peer deeper into galaxy clusters: as well as using visible telescopes to see the galaxies themselves, astronomers can map the intra-cluster gas using X-rays and reveal the black-hole driven jets capable of excavating huge bubbles in this gas using radio waves. Exploring the electromagnetic spectrum has even helped us to understand the

Universe a bit better. Data from ESA’s microwave-focused Planck satellite has produced the most detailed map of the cosmic microwave background, the afterglow of the Big Bang. And in cosmological redshift – where the light from a deep-sky object increases in wavelength so it ‘shifts’ from its anticipated position towards the red end of the spectrum – we have one of the strongest pieces of evidence for the idea of an expanding Universe. Why bother with something you can’t see indeed. S

EXPLOITING THE VISIBLE SPECTRUM The visible part of the spectrum is small, but not insignificant – there is still a lot to see. One simple way you can make the most of this narrow slice is by controlling which wavelengths you see using filters. For example, light pollution filters transmit a broad band of wavelengths, but block the ones commonly produced by streetlights to give you a clearer view. Filters with narrower wave bands may only let through certain colours of light, which can be useful to increase contrast or enhance specific features on planets or in nebulae. For example, viewing Jupiter through a filter that only transmits blue light makes its red features, such as the Great Red Spot, stand out as dark shapes against a bright background. Even more precise filters are used to isolate individual wavelengths emitted by specific atoms, such as hydrogen, oxygen or silicon, and are particularly useful for observing emission nebulae. When it comes to the Sun, filters tuned to the deep-red wavelength of hydrogen alpha block out the brilliant photosphere to reveal solar prominences and other features in the chromosphere beneath.

Through a blue filter, Jupiter’s Great Red Spot appears much more distinct

skyatnightmagazine.com 2013

NASA/ESA/STSCI/HESTER & SCOWEN (ARIZONA STATE UNIVERSITY), VLT/ISAAC/MCCAUGHREAN & ANDERSEN/AIP/ESO, ESA/ISO/PILBRATT ET AL, PETE LAWREMCE

M16’s iconic Pillars of Creation: even a small jump from near to mid infrared has a dramatic effect ESO, FAR-INFRARED: ESA/HERSCHEL/PACS/SPIRE/HILL/MOTTE/HOBYS KEY PROGRAMME CONSORTIUM/X-RAY: ESA/XMM-NEWTON/EPIC/XMM-NEWTON-SOC/BOULANGER,

We can ‘see’ the non-visible wavelengths of the electromagnetic spectrum using dedicated professional telescopes. Radio waves can be recorded using single dishes or arrays spread over large areas, but most other wavelengths are heavily absorbed by Earth’s atmosphere and must be observed from balloons, rockets or satellites. Why bother? Because observing at multiple wavelengths provides astronomers with a more complete view of the cosmos. In fact, many types of celestial object can only be seen in non-visible light. An optical telescope, no matter how large, would not be able to detect gamma-ray bursts, the most energetic explosions in the Universe – as their name implies, astronomers need a dedicated gamma-ray telescope. Likewise, radio telescopes are required to detect the jets and lobes fired hundreds of thousands of lightyears into space by the supermassive black holes at the centre of radio galaxies. Even the objects we can see in the visible part of the spectrum benefit from further study. Clouds of cold dust and gas in the Milky Way and other galaxies block visible

82

SKILLS WARNING

How to

observe the Sun safely With Pete Lawrence

Do not look directly at the Sun with the naked eye or any unfiltered optical instruments

You don’t need a dedicated solar scope to explore our parent star

TOOLS AND MATERIALS

CARD

An A2 sheet of thin, bendable card cut into 50mm-wide strips forms the filter’s slip-on wall RULER AND PENCIL

Essential to enure you mark out the card and solar film to the correct size, making the filter safe to use SCISSORS

ALL PICTURES: PETE LAWRENCE

Make sure they are sharp so you don’t damage the solar film as you cut A white light filter reveals the majesty and wonder of our star without putting your eyesight at risk

STICKY TAPE

T

SOLAR FILM

he Sun is a very gratifying object to observe. It is dynamic, with features on its visible surface that sometimes appear to change over the course of just a few hours. It is also rather convenient in that you can only observe the Sun during the day when it is generally warm – this is the comfortable side of astronomy! Being so close, our star offers us a unique opportunity to study a stellar body in detail. However, this closeness also carries danger with it, so you need to be very careful when attempting to view the Sun through a telescope. There are various ways to do this, but the safest is to fit a full-aperture white light filter over the front end of your telescope tube. The skyatnightmagazine.com 2013

term ‘white light’ means that you’ll see the Sun as it is normally, but filtered and greatly dimmed to protect your eyes. The resulting view has good contrast and neutral colour. These filters can be bought ready-made, but they are relatively simple to make yourself using sheets of solar film cut to size. Baader Planetarium’s AstroSolar film is available in two grades: OD 3.8 is for imaging only, while OD 5.0 is suitable for visual observing and imaging. OD stands for ‘optical density’ – the higher the number the dimmer the image. Thousand Oaks Optical also supply solar film in sheets. Creating the filter will take about an hour. In addition to the solar film, you’ll

Both normal and double-sided tape are invaluable for easy construction The main filter material is generally available in A4 sheets, but is sometimes available in larger rolls

also need some thin card, sticky tape and double-sided tape. Once built, your solar filter will be able to convert a regular astronomical telescope into one suitable for white-light solar viewing. It’s worth checking the

SKILLS MAY 83

filter for pinprick holes and tears each time you’re about to fit it. To do this, simply hold it up to the Sun and inspect it visually. If you find any, discard the filter and make a new one. When you use the filter, it’s important to remove or cap your telescope’s finder. This prevents it from being damaged by the Sun’s intense rays and removes the urge to look through it to line up the main instrument! Always make sure the telescope is pointing away from the Sun before fitting the filter. When you’re done observing, do the same – aim the telescope away from the Sun before removing it.

STEP-BY-STEP GUIDE

STEP 1

STEP 2

If your telescope aperture is too big to entirely cover with solar film, you can use a mask made from stiff card to cover over it; then cut a smaller hole in this mask and cover that with solar film. Make sure that the mask fits over the entire aperture and that no light can leak around its edges. For telescopes with a central obstruction, such as reflectors or Schmidt-Cassegrains, cut the aperture hole off centre so the secondary mirror doesn’t block it. Once the filter’s fitted, you’re ready to view the beauty of the white light Sun. With it, you’ll see dark sunspots and bright faculae embedded within the shaded edges of the Sun’s disc, a real effect known as limb darkening. Sunspots generally occur in groups or active regions. A typical sunspot has a dark inner area, the umbra, surrounded by a lighter one, the penumbra. The visible surface of the Sun is called the photosphere. A 6-inch telescope should reveal it as a fine, rice-grain pattern called solar granulation. This represents the tops of vast energy-transferring convective cells working beneath the Sun’s surface. Keeping a daily record of the Sun’s activity is a great way to create a connection with our nearest star. Over the course of a few days, you’ll start to reveal the dynamic changing nature of its ‘surface’ features and reveal just how these features appear to rotate across the Sun’s disc. S

STEP 3

STEP 4

FIND OUT MORE

STEP 5

STEP 6

Keep it covered

◆ For solar film, check out www.baaderplanetarium.com/sofifolie/sofi_start_e.htm and www.thousandoaksoptical.com ◆ For daily updates of what the white light Sun looks light and notification of important activity, visit www.spaceweather.com

Mark a piece of card into 50mm-wide strips, then cut them out and tape them together end to end to form one long strip. Your combined strip needs to be long enough to wrap around your telescope tube at least three times.

Measure the outer diameter of your telescope tube. Sandwich the solar film between two pieces of thin card and mark a square with sides equal to the tube diameter plus 2.5cm. Cut out this layered square, then remove any protective sheet that may be on the film.

Cut out another set of 50mm-wide strips of card and join them end to end as in Step 1. Attach double-sided tape to this card and wrap it around the card ring and solar film assembly from Step 4. Tape down the end of the card strip to finish the filter off.

Place double-sided tape at regular intervals on one side of your card strip. Wrap the strip around the tube, tape facing outwards – the tape will stick it all together, creating a ring. Don’t make this overly tight as you need to able to slip it on and off the telescope.

Fit the card ring from Step 2 to the telescope and apply four pieces of double-sided tape to it. Point the scope skywards, carefully place the film over the card ring and press it down so it sticks. Use regular tape to secure the film to the card ring so there are no gaps.

Check filter for holes by holding it up to the Sun. Discard and remake if you find any. If it’s good, point the scope away from the Sun, fit the filter and remove any finderscopes. Aim the scope at the Sun using its shadow as a guide – then you can insert an eyepiece.

skyatnightmagazine.com 2013

Astronomy

Friendly Advice and After-Sales Service. Buy online with confidence or visit our well stocked showrooms. Birstall, West Yorks WF17 9ES 01924 477719

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Sussex Astronomy Centre Meade Advanced Product Dealer

Free Parking Friendly personal service for ALL your astronomy needs. Celestron, Sky-Watcher, Meade main stockist for Sussex Beginners most welcome! A large range of telescopes and accessories from the world’s leading suppliers. Tel: 01903 247317 • 16 Mulberry Lane, Goring-by-Sea, Worthing, West Sussex

www.sussex-astronomy-centre.co.uk

SKILLS MAY 85

SKILLS

Sketching Splinter Galaxy

With Carol Lakomiak

NEED TO KNOW STEP 1 With an HB pencil, draw a light dot in the middle of your sketch circle and blend it with a blending stump. This represents the centre of the galaxy’s core. Then draw the brightest stars, using the patterns they form to help you judge the angles and distances between them.

NAME: Splinter Galaxy, NGC 5907 TYPE OF OBJECT: Edge-on spiral galaxy CONSTELLATION: Draco RA: 15h 15m 53s DEC.: +56° 19’ 44” TIME TO SKETCH: 1-14 May, 12am BST till 2am BST EQUIPMENT: 8-inch reflector; blending stump; H and HB pencils; kneadable art eraser FIELD OF VIEW: 30 arcminutes; 166x magnification

ALL PICTURES: CAROL LAKOMIAK

T

he Splinter Galaxy in Draco was discovered by William Herschel in May 1788; it can be found about 3º southwest of mag. +3.3 star Ed Asich (Iota (i) Draconis). You’ll need to use averted vision to sketch the Splinter Galaxy. This merely means that you shift your gaze slightly to the side of your actual target. The reason it works so well is that our central vision is dominated by colour-sensitive ‘cones’ that need light, whereas our peripheral vision is dominated by light-sensitive ‘rods’ that excel under low-light conditions. By using your peripheral vision, you’ll be able to see the galaxy better. It will look ‘bloated’, but just draw what you see – you’re detecting as much light as possible and that’s good. It takes a bit of practice to see something without looking directly at it, but after a while it becomes second nature. Before you begin, study the galaxy for a while. Take note of how long it is, how thick it is, and what its angle is in relation to the surrounding star field. Also look for the difference in brightness between the central core and the tapered edges.

Work out where the core’s brightness begins to fade and how far it actually extends towards the tips of the disc. Next, study the star field. See if there are any stellar patterns that can help you place the stars accurately and try to detect as many of the faint stars as you can. Because you’re sketching a negative image, the brighter core needs to be drawn darker than the outer edges. But under the red light it’s quite easy to apply too much graphite to nebulous objects like this one. If this happens, fix it by flattening a kneadable eraser and pressing it against your sketch. Lifting the eraser will gently remove a layer of graphite, so the galaxy will appear dimmer and less intense. Remember that graphite smudges easily, so be careful not to rub your hand on the galaxy while populating the star field. There are actually two ways to coat the tip of your blending stump with graphite. The first is to apply it directly. The second is make a swatch of graphite on a separate piece of paper and then rub the stump on it. Try each one in advance and pick the one that works best for you.

STEP 2 Coat the tip of your blending stump with HB graphite. Starting from the central dot, apply the graphite using small circular motions until you complete the galaxy’s core. Draw the edges by pulling some graphite outwards, fading it as you move away from the core.

STEP 3 With a sharp H pencil, add as many stars as you can detect while using averted vision. Pencil sharpness is important because faint stars need to be drawn smaller than bright ones – the same way they’re illustrated on the star charts in The Sky Guide.

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86

SKILLS

SCOPE

doctor

Our resident equipment specialist Steve Richards cures your optical ailments

I have a 3-inch Hilkin refractor from the late 1960s. Can I upgrade it for deep-sky imaging with a new Go-To mount, or is it best to buy a new scope? JIM LECKIE

PAUL WHITFIELD X 2

The Hilkin brand was indeed a popular one, manufactured in Japan – mostly likely by either Swift or Carton – and imported into Britain by the Hilkinson company of London. This 3-inch scope has good-quality achromatic lenses but a focal length of 1,000mm, giving it a slow focal ratio of f/13. The focuser is a rather basic rack and pinion type, with a focus tube designed for use with older style 0.965-inch eyepieces. Although the brand is now owned by a subsidiary of Viking Optical called Claritas Online, this specific instrument was discontinued many years ago. While its optics and long focal length make it a nice telescope for observational use, it doesn’t lend itself to deep-sky imaging. It is best used for observing the Moon and planets, and perhaps imaging these objects with a webcam. The telescope could be upgraded with a 0.965-inch to 1.25-inch eyepiece adaptor, but you would still be limited in

terms of deep-sky imaging because of the small diameter of the focus tube itself, which will introduce vignetting. A shorter focal length telescope with a larger diameter focus tube would be a far better bet for you. An excellent start for deep-sky imaging would be either a Sky-Watcher Evostar 80ED DS-Pro f/7.5 doublet refractor mounted on an HEQ5 Go-To mount or an Altair Lightwave 80ED f/6.25 doublet refractor mounted on a Celestron CGEM Go-To mount. The Sky-Watcher 80ED, left, and an HEQ5 mount, below

With Steve Richards Our Scope Doctor and all-round gear guru is a keen amateur astronomer and astrophotographer. He loves nothing more than tinkering with telescopes and accessories.

STEVE’S TOP TIP

telescope tube? Is it worth flocking the inside of a can reduce Stray light and unwanted reflections cope, but teles any ugh thro view the the contrast in g these misin especially Newtonian reflectors. Mini rving. obse your problems can certainly improve with ted pain lly usua is The inside of a telescope er furth but on, reas this just for finish a matt black e insid the ing improvement can be made by flock peel a lying app by of the telescope tube. Do this inner surface and stick black velour material to the light being of risk a is there r reve of the tube whe . reflected off it and into the eyepiece

I’m looking to buy my first telescope, but I’m confused by the amount of information online. Can you suggest something simple for £150? THOMAS PETER

With the bewildering amount of information available online, choosing a first telescope can be a confusing experience. Aperture is very important: the larger it is the greater the amount of light collected and the more objects you will be able to see. A reflector, which uses mirrors rather then lenses to focus the light from celestial objects, will give you the most aperture for your money – and the more of your money that goes into the optics, the better. It is for this reason that Dobsonianmounted telescopes [Dobsonian refers to amateur astronomer John Dobson who popularised this simple style of wooden mount] are such a good buy. Typical instruments within your budget include the Sky-Watcher Heritage 130P Flextube Dobsonian (pictured above) or – if you prefer having a reflector on a more conventional equatorial mount – either the Celestron Astromaster 130EQ or Sky-Watcher Explorer 130P EQ2.

Email your queries to [email protected] skyatnightmagazine.com 2013

SKILLS MAY 87

SKILLS

LOST IN The trials and tribulations of a novice astronomer

With Keith Hopcroft

Comet 2P/Encke making a welcome return as a support act, too. This should provide some compensation for all those uninformed,

is the difference between a meteorite and a comet?” (durr). Or “How come comets don’t move?” (double-durr). Or “Why is Comet C/2012 S1 ISON not called Comet Nevski-Novichonok?” (OK, that one is a good question – so good, in fact, that I can only respond by offering to buy a round). But the truth is, as with any febrile illness, Comet Fever bestows me with highs and lows – moments of flushed excitement, but also some shivering horror. The latter relates to the nadir of my astronomy life: 1997 and Comet Hale-Bopp. It was the most spectacular to grace our skies for decades and I was looking anywhere but up. I still have no rational explanation for this. Sure, my kids were young and distracting, my own childhood astro-interest hadn’t yet been fully rekindled, I was grumbling about being the wrong side of 35 and so on. But it is inexcusable that I didn’t see it. Not once. It was such a stunning and longstanding sight that you’d have thought I’d at least have stumbled across it inadvertently. Nope. I must have been staring at my shoes the whole time. I made up for it in October 2007 when Comet 17/P Holmes suddenly and unexpectedly went mental. My viewing notes from 29 October were ecstatic: “Extraordinary sight in Perseus. Comet visible as fuzzy star to the naked eye. No tail through scope. Hard to describe, but basically looks like a fried egg.” Even more excitement the following evening, when I claimed that it was the most amazing thing I’d ever seen - and bear in mind I once worked in an STI clinic. Maybe Comet ISON will be even more spectacular. Then again, we’ve already been spoiled by/deserve something better than C/2011 L4 PANSTARRS. Right?

“It was the most amazing thing I’d ever seen – and I once worked in an STI clinic” near-closing-time, one-too-manyshandies questions I’ve had to endure from my glassy eyed friends when they suddenly remember that I have an interest in astronomy. Such as, “So what

Keith Hopcroft is a GP and a national newspaper columnist skyatnightmagazine.com 2013

WILL HOPCROFT, ILLUSTRATION BY JEFF PARKER

H

ow are you enjoying the year of the comet? Trouble is, I’m writing so far in advance of the event (that’s magazine deadlines for you) that Comet C/2011 L4 PANSTARRS will have been and gone by the time you read this. So please delete as applicable. Wasn’t it marvellous/a complete let down? Weren’t those images amazing/ frankly disappointing? And doesn’t it make you glad to be an astronomer/rue the day you ever set eyes on a telescope? Anyway, there’s more to come/all is not lost. Because we still have the potentially uber-spectacular Comet C/2012 S1 ISON to look forward to in November, with

Astronomy insurance as little as £20 per year Protect your equipment in case of damage or theft Low excess • Specialist policy No need to claim on household policy protecting NCD

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REVIEWS MAY 89

Reviews Bringing you the best in equipment and accessories each month, as reviewed by our team of astro experts

98

HOW WE RATE Each category is given a mark out of five stars according to how well it performs. The ratings are:

★★★★★ Outstanding ★★★★★ Very good ★★★★★ Good ★★★★★ Average ★★★★★ Poor/Avoid

Find out why the chunky Orion Optics AG12 continues to impress astro imagers

This month’s reviews

PAUL WHITFIELD X 4

First light

90

Sky-Watcher Heritage-90 Virtuoso scope

94

The new Celestron AVX Go-To mount

Tried & tested

Books

Gear

98

102

104

Orion Optics AG12 12-inch Newtonian astrograph

We rate four of the latest astronomy titles

Including this Vixen Polarie polar scope

Find out more about how we review equipment at www.skyatnightmagazine.com/scoring-categories skyatnightmagazine.com 2013

90

SKY SAYS… Simplicity is the key with this altaz mount and anyone looking for a first scope will appreciate this

FIRST light Sky-Watcher

Heritage-90 Virtuoso An easy to use starter scope that promises a great deal – but doesn’t quite deliver WORDS: ANDREW PHETHEAN

VITAL STATS • Price £199 • Optics MaksutovCassegrain • Aperture 3.5 inches • Focal length 1,250mm (f/13.9) • Finderscope Red-dot • Mount Tracking altaz • Eyepieces 10mm and 25mm, 1.25-inch fit • Extras 90° mirror diagonal, camera bracket, shutter release cable for Canon DSLRs • Weight 5.1kg • Supplier Optical Vision • www.opticalvision. co.uk • Tel 01359 244200

M

any new telescope owners soon realise that setting up and storing a scope and all the associated paraphernalia is not necessarily straightforward. Thankfully, not all instruments fall into this category: the Sky-Watcher Heritage-90 Virtuoso is all about simplicity and portability. Its maintenance-free 3.5-inch Maksutov-Cassegrain telescope is complemented by a minimalistic altaz table-top mount. All you need to get going is a power supply and a suitable table to put it on. The whole setup can be stored fully assembled and ready to use, and is so compact it can be kept almost anywhere. On studying the manual, we were surprised to find that while it covered the mount’s operation in detail, there were no instructions for setting up and using the telescope itself. For a scope particularly suited to beginners, this is an unfortunate oversight. We struggled to set the latitude because the instructions for the mount were not particularly clear, but we managed to get it tracking correctly eventually. We slewed to Jupiter and centred it in the included 25mm eyepiece, giving 50x magnification. The scope showed the gas giant’s bands and the four Galilean moons. To get a closer look, we switched to the other supplied eyepiece, a 10mm, increasing the magnification to 125x. We found it difficult to snap to a clear focus as the movement was quite coarse and the focus knob rather small, but it became easier with practice. The scope is

PAUL WHITFIELD X 2, STEVE RICHARDS

SIMPLICITY ITSELF Simplicity is the key with this table-top altaz mount and anyone looking for a first scope will appreciate this. No faffing with extending tripod legs – just place it on a table small enough that you can get to the scope from every side. Aligning it couldn’t be simpler: if you are in the northern hemisphere, just point it at Polaris then turn it on. To point the scope, all you do is loosen the axis clutches and swivel the scope in altitude (up and down)

skyatnightmagazine.com 2013

or azimuth (left to right) to where you want the scope to point, then re-tighten; the mount automatically starts tracking. You can then fine-tune the position with the keypad. The axis clutches have generous grips, so they are easy to use with gloves on, and the swivelling movement is smooth and easy to control. You need to level each time you set up, but a circular spirit level and the threaded levelling feet make this a simple process.

factory collimated and non-adjustable, but assuming the telescope doesn’t suffer any serious knocks, the optics should retain alignment.

Table-top tour We noticed that although the tracking was helping to keep Jupiter in the field of view, over a few minutes it drifted out and we had to re-centre it. Tracking is set to stop automatically after 30 minutes, which can be inconvenient if you want to take a break and come back to an object. Using the keypad to change speed settings and slew the scope was straightforward and soon became second nature. At the highest slew speed, the mount was reasonably quiet, so your neighbours should sleep soundly when you stay up into the small hours. As a bonus, the mount has a port for a SynScan AZ handset, giving you the option to turn this into a full Go-To mount. Next we slewed to the first quarter Moon to explore the craters along the terminator. Although enjoyable, the view was not quite as sharp as we would have liked, showing minor astigmatism. The mount tracked reasonably well even though we slewed manually: the dual-encoder technology does its job. We then centred the Orion Nebula and were treated with a satisfying rendition of this famous view – swirling nebulosity surrounded the four stars in >

FIRST LIGHT MAY 91

KEYPAD Just nine buttons control all of the mount’s functions and settings. At first you will need to refer to the instructions regularly for the key combinations, but for the basic functions this is quick to master. The chunky buttons are backlit and easy to use while wearing gloves.

VIXEN DOVETAIL SADDLE The mount possesses a standard Vixen dovetail saddle to hold the scope. This is a versatile fitting, which means you could also use the mount for binoculars or a short refractor. It was easy to adjust the scope’s balance thanks to the secure thumbscrew.

SYNSCAN PORT The mount automatically tracks objects, but it can be upgraded to a full Go-To by connecting a SynScan AZ hand controller. With this attached, the mount will be able to automatically point at any of 40,000-plus objects in its database or take you on a tour of the best objects in the night sky.

skyatnightmagazine.com 2013

92 FIRST LIGHT MAY

FIRST light

RED-DOT FINDER The finder projects a red dot onto a glass screen, making it appear as if the dot is superimposed on the night sky. Once aligned, this is a very intuitive tool for placing objects in the field of view and is surprisingly reliable. Just remember to switch it off after use to avoid wearing down the battery.

SKY SAYS… Now add these: 1. Sky-Watcher 2x Deluxe Barlow lens 2. 7Ah power tank 3. Electronic shutter release cable

A camera can be attached to the mount using the supplied bracket, which will support a lightweight DSLR setup. The mount also offers some nifty userprogrammable photography functions and automatically triggers the camera shutter via a SNAP port.

skyatnightmagazine.com 2013

VERDICT BUILD AND DESIGN EASE OF USE FEATURES OPTICS TRACKING ACCURACY OVERALL

★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★

ALL PHOTOS: PAUL WHITFIELD

CAMERA MOUNT

> the trapezium at the nebula’s core – showing what this telescope’s modest aperture is capable of. Unfortunately our fun was cut short when the front lens began to frost up. This is because the lens is very close to the front end of the scope, so it is completely exposed. Sky-Watcher could have remedied this by including a detachable dew shield. The mount itself is built from substantial laminated chipboard. It is very sturdy, but needs to be stored in a dry environment to prevent water damage. The mount has several extra photography and video recording features. For example, it can choreograph panoramic shots, so you can photograph a wide landscape with multiple panes, or it can pan gradually through up to six programmable positions. We had to study the manual carefully to set these up, but they worked well in general. None of these features are really relevant to astronomers and, as it is an altaz mount, it is not suitable for long-exposure imaging, but no doubt some will find these extras useful. Accompanied by more complete instructions or a knowledgeable friend, the Heritage-90 Virtuoso would make a good first scope for a budding astronomer. Its simple operation makes for a gentle learning curve, and its 3.5-inch aperture is sufficient to reveal a wealth of detail within the Solar System and beyond. S

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94

FIRST light Celestron AVX

Go-To mount

SKY SAYS… The mount feels substantial and well designed, with all of its electronics integrated apart from a short lead

An exceptionally solid mount with outstanding Go-To capabilities WORDS: STEVE RICHARDS

VITAL STATS • Price £839 • Load capacity 13.6kg • Hand controller NexStar+ EQ08 • Database 40,000-plus objects • Flash upgradable Yes • Autoguider port ST4 • Tripod Two-inch tubular steel • Weight Mount: 7.7kg plus counterweights Tripod: 8.2kg • Supplier David Hinds • www.celestron.uk.com • Tel 01525 852696

C

elestron’s AVX mount is a significant update to the popular CG5-GT. Attractively finished in the familiar black and orange livery, the mount feels substantial and well designed, with all of its electronics integrated apart from the short lead that connects the declination axis to the main controller. It arrived in a single large cardboard box, which contained the mount head, tripod, counterbalance weight, hand controller, cables, 33-page manual and a copy of Software Bisque’s planetarium software TheSkyX First Light Edition. Assembly was straightforward – the mount attached to the heavyweight tripod with a single central bolt that also supports the tripod’s metal leg spreader. An alignment peg to work the azimuth adjustment bolts against can be placed either above one leg or in between two legs. We chose the former position so that we had a north-facing leg, allowing us to perform a quicker rough polar alignment and making it easier to kneel behind the mount to sight Polaris through the right ascension axis. The declination axis has a 105mm Vixen-style dovetail clamp, with two bolts to hold a telescope’s dovetail bar solidly. We used our own Vixen-toLosmandy saddle clamp adaptor to attach our own telescope, a William Optics FLT 98 refractor, which has a Losmandy dovetail bar.

ALL PHOTOS: PAUL WHITFIELD

ALL-STAR SOLUTION Precise polar alignment is vital for accurate Go-Tos and long-term tracking, but using a polarscope can be uncomfortable, and involve kneeling on the cold ground while squinting though the polarscope at an awkward angle. The AVX solves this very neatly with a routine called ‘All-Star’. All-Star polar alignment is an extension of the normal two-star alignment process. Start by performing a rough visual polar alignment – we found Polaris through the empty polarscope slot. Carry out a

skyatnightmagazine.com 2013

standard two-star alignment using the direction keys, then choose a third star on the opposite side of the meridian to align on, called a ‘calibration star’. Slew to it and centre using the direction keys again. Finally, choose another bright star, slew to it, select Polar Align and centre it. The mount will re-slew to this star while applying a pointing correction and request you to re-centre it using the altitude and azimuth adjustment bolts. The mount is now polar aligned.

The main body of the right ascension axis contains an on-off switch and five RJ-type ports. Three are for the hand controller, ST4 guider and the declination axis connection, while the remaining two are auxiliary ports. We were pleased to see that the supplied cigarette lighter-style power lead had a locking collar on the mount end, ensuring that it can’t be pulled out in error. The NexStar+ hand controller has an RS232 port for PC connection, though bizarrely the version of TheSkyX software supplied does not support mount control.

Altitude adjustment The mount’s altitude can be adjusted to match a given latitude using two substantial opposing hand bolts, which have good grips. These were a little tight in operation, but they did allow for accurate adjustment and setting. There are also substantial hand grips on the azimuth bolts, which were much appreciated when setting up in the cold. The etched latitude scale accurately displayed our true latitude following polar alignment. With our refractor weighing in at 5.2kg, plus the weight of an Altair Astro 60mm finderscope, the single 5.4kg counterbalance weight was only just enough to balance the right ascension axis when positioned at the very end of the counterbalance bar. Both axes had excellent and solid clutch actuation >

FIRST LIGHT MAY 95

COUNTERWEIGHT The 20mm diameter counterweight bar is non-retractable and attaches firmly to the base of the right ascension axis with a heavy-duty thread. The single 5.4kg weight has a simple sculpted finish rather than the usual plain cylindrical design. There’s also a substantial ‘toe protector’, which screws into the end of the shaft in case of any mishaps.

ST4 PORT Even periodic error correction doesn’t remove all the mount’s tracking errors, so there is an industry-standard ST4 guide port built in. This, coupled with an off-axis guider or guide scope, will correct any residual tracking errors and ensure that stars appear sharp and well-shaped in your images.

HAND CONTROLLER The NexStar+ hand controller has backlit buttons and a two-line red LED display. It has an excellent database of more than 40,000 objects and a back-up battery that maintains a real-time clock – so you don’t have to re-enter the date and time each observing session.

TRIPOD The supplied tripod is very substantial, with heavyweight two-inch tubular stainless steel legs and a robust head. Even with the legs fully extended, the mount remains rigid in use – something helped by the metal leg spreader, which doubles as an accessory tray. It holds two 2-inch eyepieces and five 1.25-inch eyepieces.

skyatnightmagazine.com 2013

96 FIRST LIGHT MAY

FIRST light

ALTITUDE AND AZIMUTH ADJUSTMENT KNOBS It’s very important to obtain an accurate polar alignment but getting this right requires very small mechanical adjustments. The AVX’s large, chunky adjustment knobs, which move the mount in both altitude and azimuth, help in this task enormously, especially when wearing gloves.

SKY SAYS… Now add these: 1. Aux port splitter cable 2. StarSense accessory 3.17ah power tank

> knobs that could be operated while wearing gloves. The hand controller’s well-established two-star alignment routine works very well indeed, but the addition of All-Star polar alignment simplifies the whole alignment process even further, removing the need for a polarscope. We were impressed with the high level of accuracy of each Go-To after we had carried out the alignment process, and the motors were reasonably quiet when slewing and silent once tracking. Both deep-sky and Solar System objects, no matter where they were located in the sky, appeared very near to the centre of our 17mm eyepiece after each Go-To request. Even with our 5mm eyepiece, each Go-To resulted in the object appearing comfortably within the field of view – even when a meridian flip was required to reach the object. Tracking accuracy was excellent, with our test star remaining in the centre of our 17mm eyepiece for well over an hour. The heavyweight tripod made the whole system very solid and helped to dampen any vibrations, which made focusing our refractor very easy. We very much enjoyed using the AVX and would recommend it to both beginners and intermediate observers looking for a solid, accurate but transportable mount. S

VERDICT ALL PHOTOS: PAUL WHITFIELD

ASSEMBLY BUILD AND DESIGN EASE OF USE GO-TO ACCURACY STABILITY OVERALL

skyatnightmagazine.com 2013

★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★

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5 Individual secluded lodges in Mid-Wales hill top setting. Exceptional views across tranquil valley and dark night sky. Realistic rates for your telescope and you. Lat 52.355209, Long -3.294268

01597 840308 ✴ www.radnor-revivals.co.uk

98

TRIED & tested

We review well-established equipment that’s stood the test of time

VITAL STATS

PAUL WHITFIELD X 3, MICHAEL SODONIO X 2

• Price £5,995 telescope only, £7,870 including Losmandy G-11 mount • Aperture 12 inches • Optical design hand-figured primary mirror corrected to one-eighth of a wavelength, 4.5-inch secondary mirror • Focal length 1,140mm (f/3.8) • Focuser Crayford-style Baader Steeltrack with 1:10 microfocuser • Weight 28.1kg • Extras Tube-rings, mounting plate • Supplier Orion Optics • www.orionoptics.co.uk • Tel 01782 614200

SKY SAYS… The fidelity was very impressive, with sharp stars visible right across our camera’s frame

Orion Optics AG12

12-inch astrograph The shots from this cannon-sized scope will blow you away WORDS: PETE LAWRENCE

T

he AG12 is a Newtonian astrograph, an instrument designed specifically for imaging stars and deep-sky objects. It has a generous 12-inch aperture, making it a veritable light bucket, and a focal length of 1,140mm – this a fast scope with a focal ratio of f/3.8. The full AG series includes models with apertures ranging from 8 inches to 16 inches. All come with hand-figured primary mirrors, corrected to one-eighth of a wavelength. The primary and secondary mirrors have Hilux-enhanced aluminium coatings, offering 97 per cent reflectivity across most of the visible spectrum. Reflectors are ideal if you want a large aperture instrument at relatively low cost, but they can suffer from poor off-axis performance, resulting in badly shaped stars towards the edge of the field of view. Orion Optics address this issue in the AG12 with a custom field flattener, the design of which is based on what’s known as a Wynne Corrector – named after the huge 200-inch reflector on Mount Palomar in California that used such a device to provide a corrected wide-field view. The corrected field flattener supplied with the AG12 is 180mm long, 85mm in diameter and weighs 1.3kg. It slides into the supplied Baader Steeltrack focuser, screwing securely into position. A custom adaptor, also supplied, allows you to connect the field flattener to a DSLR or cooled CCD camera. The AG12 can also be used visually without it.

Weighty beast The scope arrived in a deconstructed state, so we had to do a bit of simple assembly to connect the primary mirror cell, secondary mirror and focuser to the sturdy carbon-fibre optical tube. Assembly was pretty straightforward and we soon had the scope sitting on our own Losmandy G-11 mount, chosen because the AG12 is also available as a package including this accessory. The optical tube attaches to the mount using a tube-ring cradle, supplied as standard. skyatnightmagazine.com 2013

Collimating the reflector was a relatively easy task, although having a second pair of hands is a great help here. The secondary mirror is held in place by three adjustment screws and is simple to orientate. The primary mirror is supported by a nine-point suspension unit and adjusted using three pairs of lockable bolts. There did seem to be a minor issue with the paint on the ring holding the primary in place within its cell – several small black specks of it had fallen on the mirror surface. Three 12V cooling fans on the base of the mirror cell help to rapidly bring the scope to observing temperature. A heating band is also built into the carbon-fibre tube to help keep dew from forming on the primary mirror. A 315mm extension tube is provided as well; it’s fitted to >

TRIED & TESTED MAY 99

OWNER’S OBSERVATIONS Name Michael Sidonio Location Canberra, Australia Equipment Orion Optics AG12 Newtonian astrograph Owner since March 2011 I like to be able to tackle wide fields to image larger nebulae and star clusters, but I also like to be able to capture fine details in galaxies and planetary nebulae if I choose. Over the past 18 months the AG12 has proved to be a reliable and versatile instrument. With my large FLI PL16803 CCD chip I have a whopping 2.6º diagonal field of view at an ideal image scale of 1.6 inches per pixel, so I can take both wide-field and

high-resolution images. Because this is a fast astrograph, I have found that in exposures collected in half a single clear night I can go as deep as the largest Schmidt-Cassegrain telescopes at professional observatories did just a generation ago, while the focal length and resulting resolution is more than sufficient to reveal fine details in distant galaxies. This versatility has revolutionised my imaging and has made me very happy. The scope is beautifully constructed, easy to collimate and considering its aperture is very portable. To me the AG12 Michael’s stunn ing truly is a shot of the Eta Carina Nebul dream scope. a

PRIMARY MIRROR The 12-inch parabolic primary mirror is hand-figured to an accuracy of one-eighth of a wavelength or better. As is the case with the flat secondary mirror, this mirror is Hilux-coated to give up to 25 per cent better reflectivity than conventional coatings.

MIRROR CELL The primary mirror cell provides a strong, adjustable support for the main mirror. The mirror itself is held in place by a nine-point suspension cell, which balances the weight of the mirror better than a conventional three-point cell, providing results that are better defined. Collimation is performed using three pairs of adjustment screws at the rear of the cell.

skyatnightmagazine.com 2013

100 TRIED & TESTED MAY

TRIED & tested FOCUSER The mechanism of the supplied Baader Steeltrack focuser is based on the Crayford design and provides smooth focusing action throughout its 115mm of travel. A 1:10 fine-focus mechanism is provided, as well as a locking screw.

TELESCOPE TUBE The AG12’s optical tube is made from a carbon-fibre sandwiched material and provides a strong support for the telescope’s optical components. This choice of material removes focus problems caused by thermal expansion and is virtually flex free. The inside of the tube is matt black, reducing internal reflections. The AG12 captured the majesty of the Orion Nebula in a single shot exposed for the core only

CORRECTED FIELD FLATTENER The corrected field flattener is an optical device designed to compensate for the aberrations inherent in the reflector design. It works with both DSLRs and cooled astronomical CCD cameras.

SKY SAYS… Now add these: 1. Dew shield

PAUL WHITFIELD X 2, PETE LAWRENCE

2. FLI Atlas digital focuser 3. FLI ProLine cooled CCD camera

skyatnightmagazine.com 2013

> the main tube to further reduce the likelihood of internal dewing. The scope is heavy – it appears to be fractionally over the limit of the Losmandy G-11’s 27.2kg stated instrument weight capacity. Our measurements put the assembled telescope, including tube rings and the corrected field flattener, at 28.1kg. Attaching a camera, guide scope and finder would all add additional weight. After some careful balancing to secure our own DSLR and guide scope, we focused the AG12 and started imaging. The field around open cluster M35 in Gemini gave us a good spread of stars right to the corner of our DSLR’s sensor. The fidelity was also very impressive, with sharp stars visible right across the frame.

With its 12-inch aperture, the AG12 can really pull in a lot of light quickly. We couldn’t resist using it on a couple of popular nebulae, including the Orion Nebula and its close neighbour, the delightful Running Man Nebula. These bright objects pose no problem for the AG12, but we were nonetheless impressed by the amazing amount of peripheral nebulosity brought out from a single 18-second DSLR exposure originally set to record just the core of the Orion Nebula. With rich star colours in the heart of clusters like M35, the superb corrected field flattener appears to produce no noticeable chromatic aberration. Weighty though it is, the AG12 is a superb deep-sky imaging platform with impressive optical performance. On a heavy-duty permanent observatory mount, it represents a tough act to follow. S

VERDICT BUILD AND DESIGN EASE OF USE FEATURES IMAGING QUALITY OPTICS OVERALL

★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★

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102

Books New astronomy and space titles reviewed

Are We Being Watched?

THINKSTOCK

Paul Murdin Thames and Hudson £16.95  HB This century, says Are We Being Watched? author Paul Murdin, is the one in which we will find life on other worlds. Astrobiology is the name of the science engaged in this search, though as Murdin rightly points out, it is a science The final chapters take us on a tour of that has yet to demonstrate its subject the Solar System, examining some of the matter even exists. In this book, he other planets and moons that have the explains the latest discoveries that potential to harbour life. We look at the nonetheless give us cause to hope. story of Mars’s past climate, peer under Murdin explores how life might have Europa’s surface shell of ice to the dark got started on planet Earth: were the ocean sloshing beneath, admire crucial organic molecules the extraordinary fountains perhaps delivered from of water jetting from the outer space aboard interior of Enceladus, asteroids and comets, and visit the frigid, or the result of home methane-soaked cooking, possibly landscape of Titan. within hydrothermal What book could vents deep on the have benefitted from, sea floor? He also however, is a stronger discovers how sense of structure. terrestrial life and the Topics seem scattered world we live in have into chapters without evolved together over much sense of each chapter billions of years; ways in which life has modified If there is life elsewhere, building on the one before. For is it intelligent enough example, the possibility of alien the atmosphere, oceans to spy on us? intelligence and what it might and land – the fabric of the look like is discussed before simpler, planet itself – and conversely what hardier single-celled life and there is little effects changes on Earth have had on feeling of an argument gathering the life smeared across its face. momentum to the conclusion. Threats to life on a planet include violent stars, asteroid impacts and ice ages ★★★★★ that cause the surface of the entire planet to freeze over – all of which have affected LEWIS DARTNELL is an astrobiology Earth. Murdin also provides an updated research fellow at the University of Leicester summary of the hunt for planets orbiting other stars, as we get ever closer to Reader price £14.99, subscriber price £13.99 locating Earth’s twin. P&P £1.99 Code: S0513/1 skyatnightmagazine.com 2013

RATINGS ★★★★★ Outstanding ★★★★★ Good ★★★★★ Average ★★★★★ Poor ★★★★★ Avoid You can order these books from our shop by calling 01803 865913

2 MINUTES WITH PAUL MURDIN What inspired you to write this book? I am an astronomer and I am wedded to the idea that I am a part of the Universe, not apart from it. I wanted to explore the concept of planetary systems like ours as ecosystems, providing the environment in which life has developed, on Earth and possibly other planets too. Did anything surprise you while you were researching the book? I had not realised that we had got so close so many times to proving that life exists elsewhere in the Universe and then had to draw back from certainty. Early radio experiments, Martian soil chemistry, Martian meteorites, the Wow! radio signal – they looked promising and then hope dissipated. I also realised that we have been concentrating too much on the physical circumstances where we might find life and not enough on the time it takes for life to evolve. It seems to me that there are lots of places where life could exist, but generally there has been too little time for intelligent life to evolve there. Where in our Solar System should we be looking for extraterrestrial life? Undoubtedly Mars, in some niche environments into which early Martian life took refuge. Enceladus is also a good place to look, in the spray from the geysers. Are we close to finding life elsewhere? I doubt we will find life outside the Solar System for a very long time, if ever, not because life doesn’t exist there but because it is so hard to find it. PROF PAUL MURDIN is an astronomer at the Institute of Astronomy at the University of Cambridge

BOOKS MAY 103

Spacesuit: a History Through Fact and Fiction Brett Gooden Tattered Flag Publishing £16.99  HB Astronauts make spacewalking look easy. Donning the one-man spacecraft that make spacewalks possible is anything but. In fact, astronauts start the training exercises to build the extra muscle power needed to work inside a spacesuit a year before an assignment begins. This authoritative but readable book recounts the origin and tangled evolution of spacesuits, while also making it clear why they remain so hard to wear. Fundamentally, spacesuits have two contradictory tasks to accomplish: keep the human body pressurised in a vacuum; and allowing as much movement as possible. The first task requires a balloon-

The Universe Within: A Scientific Adventure Neil Shubin Allen Lane £20  HB

OKE BO F TH

O N TH MO

Have you ever felt deeply connected to everything else in the Universe? If not, you could visit a spiritual coach. Or you could read American palaeontologist Neil Shubin’s marvellous book about the relationship between our own existence and the cosmos we inhabit. Shubin wields a lucid, captivating pen. Weaving together personal field notes of his expeditions to the Arctic, historical anecdotes, the latest scientific insights and almost philosophical musings, he takes his readers on a fascinating trip through the history of the Universe, the geology of our home planet, and the rise and evolution of complex organisms like Homo sapiens.

like bladder, which is where the difficulty comes in. Simply bending a balloon takes a lot of effort. Get the pressure too high and the wearer could find themselves immobilised like the first spacewalker Alexei Leonov, who had to partially deflate his spacesuit just to fit back inside his spacecraft. The second task implies an extra constraining layer, plus flexible joints – not to mention several insulating and protective coatings. Engineers have been tackling this challenge for eight decades. Spacesuit author Brett Gooden argues that early science fiction helped inspire actual suit designs – with sci-fi authors Robert Heinlein and L Sprague de Camp working on secret flying suits during World War II. The result is a lavishly illustrated publication put together with palpable enthusiasm, incorporating pulp art as well as rare aerospace photos – recounting the strengths and weaknesses of the real and imaginary suits on show.

★★★★★ SEAN BLAIR is a space writer and journalist Reader price £15.99, subscriber price £14.99 P&P £1.99 Code: S0513/2

The recurring lesson: we are what we are because our physical environment changed the way it did. Supernovae produced the elemental building blocks of life; drifting continents and cosmic impacts opened up new evolutionary alleys; ice ages promoted the development of stable societies. One surprising example is the ‘invention’ of colour vision, some 40 million years ago. It enabled primates to select the most nutritious leaves, which was very important during periods of huge change in climate and flora. “Every time you admire a richly colourful view, you can thank India for slamming into Asia, continents for retreating from Antarctica and the poles for becoming frozen wastes,” writes Shubin. While this book is more about our planet (and its inhabitants) than about stars and galaxies, it’s a worthy read for any astronomy aficionado. It will change your perspective on our own place in the bigger Universe.

Total Addiction Kate Russo Springer £16.95  PB Kate Russo is an eclipse chaser. Having been bitten by the bug after witnessing her first total eclipse from France in 1999, she has gone on to observe seven more totalities. As a psychologist, Russo was struck by what drives and motivates eclipse chasers to “stand under the shadow”, and that is the basis for her book. Russo explores the subject matter with passion and enthusiasm. There is a breakdown of how total eclipses occur and the basic science behind them, although it would have been nice to see more diagrams in this section. What follows are interviews with nine eclipse chasers of varying degrees of experience, the first being the late Sir Patrick Moore. She then offers an insight into the context, comparing how we view an eclipse both spiritually and scientifically in an attempt to decipher why totality has such a powerful effect on some people. Her journey ends with information for upcoming eclipses and her final conclusions as to why some people dedicate so much time to chasing them. Reading this book brought back strong memories of the eclipses that I have been lucky enough to see – it is certainly a book from which nonstargazing friends and family would gain a greater understanding of why eclipses hold such allure. Although words will never fully capture the magic of this phenomenon, Total Addiction is the closest you can get to understanding the power of totality without actually being there.

★★★★★

★★★★★

PAUL MONEY is Sky at Night Magazine’s reviews editor

GOVERT SCHILLING has written more than 40 astronomy books

Reader price: £14.99 subscriber price: £13.99 P&P £1.99 Code: S0513/3

Reader price £14.99, subscriber price £13.99 P&P £1.99 Code: S0513/4

skyatnightmagazine.com 2013

104 GEAR MAY

Gear EYEPIECES FOR ILLUSTRATIVE PURPOSE ONLY

Vincent Whiteman rounds up the latest astronomical accessories

1

4 1 Q-Turret Quadruplet Eyepiece Revolver

Price £70 • Supplier The Widescreen Centre 020 7935 2580 • www.widescreen-centre.co.uk Attach this four-position eyepiece holder to your setup and you’ll be able to switch between fixed focal length eyepieces on the fly. Eyepieces shown are not included.

2 Baader 6mm Classic Series Orthoscopic Eyepiece Price £49 • Supplier First Light Optics 01392 826133 • www.firstlightoptics.com

This 6mm orthoscopic (distortion free) eyepiece offers a 50º field of view and has an inset rubber eye cap.

5

3 Vixen Polarie Polar Scope

2

Price £176 • Supplier 365 Astronomy 020 3384 5187 • www.365astronomy.com Designed to accompany Vixen’s Polarie Star Tracker, this red LED illuminated 6x30mm polar scope features a spirit level, time and date circles, and a meridian offset scale for different time zones.

4 Universal Dovetail Mounting Plate

Price £22.99 • Supplier Nipon Scope and Optics 0844 3187890 • www.nipon-scope.com This plate features adjustable screw positions, allowing you to secure a telescope to an equatorial tripod.

5 Outdoor Sports Mitten

3

Price £45 • Supplier SealSkinz 01553 817990 • www.sealskinz.com Keeping your hands toasty is critical for a good night’s observing. These mittens are designed for warmth, comfort and strength, with a fingerless option for when you need to adjust your setup.

6 Orion Deluxe Mini Guide Scope with Helical Focuser Price £169 • Supplier SCS Astro 01823 665510 • www.scsastro.co.uk

Featuring a helical focuser for accurate guide star focusing, this 50mm guide scope also doubles as a finderscope. It attaches to telescopes through a dovetail bracket.

skyatnightmagazine.com 2013

6

106 EXPERT INTERVIEW MAY

WHAT I REALLY WANT TO KNOW IS…

Can aurorae help us find exoplanets? Jonathan Nichols believes he has hit on a new way to detect alien worlds around nearby stars INTERVIEWED BY PAUL SUTHERLAND

A

urorae have put on spectacular sky shows on Earth throughout history. But we had to wait for the Space Age to find out that they also occur on the gas giants Jupiter and Saturn – thanks to the ultraviolet detectors on NASA’s Pioneer and Voyager probes. These days we rely on the Hubble Space Telescope – it’s very useful being able to keep track of what’s going on in their magnetic fields without needing to maintain a spacecraft out there. Aurorae are caused by charged particles being funnelled along a planet’s magnetic field towards its magnetic poles. When these particles collide with atoms in the atmosphere they release light in much the same way that a neon light bulb glows. If you imagine looking down on such a planet, you would see a ring of aurorae around the poles. Just above the aurorae in the magnetic field, beams of radio waves are being emitted. Jupiter’s aurorae are about 100 times more powerful than Earth’s because its magnetic field is much stronger than our planet’s. Strangely, we knew that Jupiter had a magnetic field in 1955, three years before the Van Allen radiation belts – which form the natural magnetic shield that protects us from space weather and helps to produce the Northern and Southern Lights – were found around Earth. That was thanks to its radio emissions, which can be as strong as the Sun’s when our star is quiet.

JPL/NASA/STSCI

Deviant waves The radio emissions from Jupiter and the Sun are different. In the case of Jupiter, the electric and magnetic fields that make up the radio waves are twisted – ‘circularly polarised’ to use the technical term. Some have radiation that is comparable to that from a star, yet easily distinguishable. With that in mind, looking for radio waves should be a good way of searching for exoplanets. skyatnightmagazine.com 2013

Hubble has spotted aurorae at Jupiter’s north and south poles, inset, in ultraviolet light

ABOUT JONATHAN NICHOLS Dr Jonathan Nichols is a lecturer and research Fellow in the University of Leicester’s Department of Physics and Astronomy, with a special interest in aurorae in our own Solar System and beyond.

Radio emissions from stars can be detected right throughout the Universe. In terms of the exoplanets we are looking for around nearby stars, the radio sources will be very dim. That’s the reason why we haven’t detected any exoplanets in this way in the past. We’re only just developing instruments sensitive enough to find them, such as the LowFrequency Array (LOFAR) for radio astronomy in the Netherlands, the UK and across Europe. What we will look for are radio emissions that are twisted first of all, but also pulsing at a rate we might expect a planet to spin. Earth spins once every 24 hours, Jupiter once every 10 hours, but the Sun spins once every 25 days or there about. So we are expecting signals that pulse every few hours rather than every few days. That will indicate whether an exoplanet is present. The type of stars we are interested in checking are the ones shining very brightly in the ultraviolet and X-ray parts of the spectrum, hotter and probably younger than the Sun with a strong magnetic field. We have time allocated on LOFAR, so we’ll soon be able to conduct a survey to see if we can find any exoplanets. There are two types we think will be detectable. One is a ‘hot Jupiter’, a planet that orbits very close to its star. On those worlds you would expect aurorae to exist as the magnetic field is buffeted by a strong stellar wind, just as on Earth. The other type is like our Jupiter, sitting farther away from its parent star, with aurorae generated not by the solar wind but by energy from the rotation of the planet itself. We don’t expect to see the aurorae visually; it is the radio signals that will beam out across space that we’re looking for. This should be a useful way of finding new exoplanets because it doesn’t rely on the planet transiting in front of its star – and we won’t have to wait 20 or 30 years for radial velocity data to confirm an orbit. S

SOUTHERN HEMISPHERE IN MAY With Glenn Dawes

00:00 23:00 22:00

HE

RC

> 1 May > 15 May > 31 May

H E AS T

The chart accurately matches the sky on the dates and times shown. The sky is different at other times as stars crossing it set four minutes earlier each night. We’ve drawn the chart for latitude –35° south.

RT O N

WHEN TO USE THIS CHART

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Many of the stars in our southern skies are not visible from mid-northern hemisphere latitudes and hence don’t have names steeped in ancient legends. The lead star in the Southern Cross asterism, mag. +1.3 Acrux, is named for a simple contraction of ‘Alpha’ and ‘Crux’. Atria is a lesser-known example, but one that makes sense looking at its name, Alpha Triangulum Australis. Some just lack imagination. Consider mag. +1.9 Peacock, the alpha star in Pavo – you can guess the animal the constellation represents.

Summer γ Triangle

On 10 May an annular eclipse will be visible from northern Australia. In this type of eclipse the Moon’s apparent size is smaller than the Sun’s, so a bright ring – an annulus – is visible during the event. The eclipse path is pretty isolated: Tennant Creek in the Northern Territory will be the most accessible spot. The rest of Australia will see partial phases, with maximum in Melbourne at 08:52 EST, Sydney at 08:57 EST, Brisbane at 08:58 EST, Hobart at 08:59 EST, Adelaide at 08:15 CST and Darwin at 08:07 CST.

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CHART CONVERSION BY PAUL WOOTTON

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skyatnightmagazine.com 2013

ASTEROID TRACK

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STAR BRIGHTNESS:

DIFFUSE NEBULOSITY

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CHART KEY GALAXY

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Look 2.2° north-northeast of Birdun to reach double star M Centauri. The primary orange star is mag. +4.5 and has a mag. +11.0 companion separated by 44 arcseconds. Only 4 arcminutes northwest is globular cluster NGC 5286, left (RA 13h 46.4m, dec. -51° 22’). This mag. +7.4 cluster shows broad central brightening; you’ll need a 6-inch scope to resolve some of the stars within it.

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with Venus being the brighter. They set early, however, and are only a few degrees above the horizon at 17:30 EST. Saturn is well placed throughout May, appearing late in the evening in the northern sky and remaining visible for most of the night.

EAST

Jupiter is in the evening twilight, shining away brilliantly low in the northwest. The end of the month sees Venus and Mercury rise out of the Sun’s glare, passing Jupiter. From the 26th to the 31st, Jupiter and Venus are less than 3° apart,

α

THE PLANETS

Centaurus is home to several lesser known but easy to find gems. Look 1.1º south of mag. +2.3 star Birdun (Epsilon (e) Centauri) to find the impressive mag. +5.2 double star Q Centauri (RA 13h 41.7m, dec. -54° 33’). You’ll need a magnification of about 150x to separate its blue mag. +5.2 and white mag. +6.2 components, just 5.5 arcseconds apart, but the view is worth it.

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skyatnightmagazine.com 2013

OFFICIAL GUIDE 17 and 18 May 2013 Warwickshire Exhibition Centre

2,000 free car parking spaces 200-seat restaurant 50 astronomy trade stands 9 amazing talks Easy access by road, rail and bus Shuttle bus from Leamington Spa train station Exhibition space all on one level

ORGANISED BY in association with

ABOUT THE SHOW THE VENUE Warwickshire Exhibition Centre is located between Leamington Spa and Coventry, and is the ideal venue to hold an astronomy exhibition. It offers: ◆ 2,000m2 of exhibition space, all on the ground floor ◆ 2,000 free car parking spaces ◆ A 200-seat restaurant

TRAVELLING TO THE VENUE UK Astronomers Ltd, in association with Sky at Night Magazine, are pleased to present the brand new International Astronomy Show. The event will be held in the heart of the West Midlands on 17 and 18 May, at the Warwickshire Exhibition Centre between Leamington Spa and Coventry. The show aims to be the biggest organised outside of London. Around 40 astronomy dealers and specialists will gather under one roof, and some of the country’s best known astronomy speakers will give talks and live demonstrations to add to the fun. The aim is to provide a value for money show, without the stress of having to travel into the centre of London. The Sky at Night Magazine team will also be on hand, so come and say hello and get the copy of the latest magazine, plus a lot more besides.

The venue’s address is: The Fosse, Fosse Way, Leamington Spa, Warwickshire, CV31 1XN There is easy access by road from the M1, M40 and M6. Typical drive times are: Birmingham: 45 minutes London: 1 hour 30 minutes Manchester: 1 hour 45 minutes Liverpool and Bristol: 2 hours Leeds: 2 hours 15 minutes The nearest train station is Leamington Spa. Warwickshire Exhibition Centre is only five miles away and we have arranged for a 26-seat shuttle bus to ferry visitors to and from the exhibition. A return ticket on the shuttle bus costs just £7. The shuttle bus will run at hourly intervals from Leamington Spa train station on Friday 17 May and Saturday 18 May, as follows: Depart Leamington Spa Station

Arrive Warwickshire Exhibition Centre

Depart Warwickshire Exhibition Centre

Arrive Leamington Spa Station

8.30 am

8.50 am

9.00 am

9.20 am

10.00 am

10.20 am

10.30 am

10.50 am

11.00 am

11.20 am

11.30 am

11.50 am

12.00 noon

12.20 pm

2.00 pm

2.20 pm

2.30 pm

2.50 pm

3.00 pm

3.20 pm

3.30 pm

3.50 pm

4.00 pm

4.20 pm

4.30 pm

4.50 pm

5.15 pm

5.40 pm

5.45 pm

6.10 pm

All times are approximate

For those travelling from further afield, Birmingham City airport is just 20 miles away. If you fancy visiting the show on both days or don’t want to travel, there are many B&Bs and cheap hotels in the area. There is also a campsite just two miles from the venue.

TICKETS There are two easy ways to purchase tickets for general entry to the show and for individual talks: 1. Online at our ticket sales website: www.international-astronomy-show.com/ticket-sales 2. At the show from the ticket kiosk. Please note: cash only (no credit cards accepted). Spaces at the talks will be limited to 100 people per session, so book early to avoid disappointment. Astronomy societies and groups can get a group discount when ordering more than 10 tickets (see website for details).

OPENING TIMES AND PRICES

BBC TV’s The Sky at Night The Sky at Night’s famous double-act reporters, Pete Lawrence and Dr Paul Abel, below, will be opening the show for us and remaining as our guests. They will be joined on the Saturday by Dr Chris Lintott, who is giving one of our talks. Chris is one of the main presenters of The Sky at Night, and co-author of the book Bang! – The Complete History of the Universe with Sir Patrick Moore and Queen guitarist Brian May. Chris, Pete and Paul will all be on hand to sign copies of their books – and maybe answer some of your questions!

The show opens at 9am and closes at 6pm on each day. The talks begin at 9.30am. Adult general admission (Fri 17th) Adult general admission (Sat 18th) Adult general admission (Both days) Under-16s general admission (Fri 17th) Under-16s general admission (Sat 18th) Under-16s general admission (Both days) Entry to each talk

£7 £7 £14 £3 £3 £6 £6

Buy your tickets online NOW!

EXHIBITION FLOOR PLAN 1 Ian King Imaging

30 British Astronomical Association

2 Astro Hutech / Borg

31,32 Modern Astronomy

3 AWR Tech / Astromount

33 Altair Astro & iOptron / Sky Shed POD

4,5,6 David Hinds Ltd, Celestron, Baader Planetarium

7,9,10,11 Telescope House 8 The Widescreen Centre 12 Starlight Xpress 13 Society for Popular Astronomy 14 APM Telescopes / Astrographs 15 SkyLight Telescopes 16 WEX / Canon 17 WEX Photographic 18 NM Southern Skies 19 Green Witch 20 Peak 2 Valley Instruments / Istar Telescopes UK 21 TBC 22 Liverpool John Moores University 23 SkyVision 24 Hitec Astro 25 Solarscope Ltd

Observatory

34 Astronomia / Home Farm Roll-Off Observatories

35 Canopus Books 36 The Sky at Night Presenters 37 Shelyak 38 Webb Deep-Sky Society 39 Astroparts / House of Optics 40 Nik Szymanek 41,42 Dr Stuart Clark / Jerry Stone 43 Space Station – Space Rocks UK 44

Pulsar Observatories Ltd

45 Cambridge University Press 46 The Open University 47 ATIK Cameras 48 Sky at Night Magazine studio 49 Sky At Night Magazine 50 StarDome Planetarium

26,27 365 Astronomy / Moravian Instruments

TABLES

28

◆ British Interplanetary Society

Vixen/Opticron

29 Explorers Astronomy Tours

◆ BAA Radio Society ◆ Moon Raker Telescope ◆ Campaign for Dark Skies

TALKS AND SPEAKERS The International Astronomy Show is delighted to welcome six key speakers to add to your enjoyment! You can purchase tickets for any of the talks from our website. Entry to each talk is £6. Friday 17 May 9.30am

1

Jerry Stone

Let’s go to Mars!

11.15am

2

Olivier Thizy

Spectroscopy with a very small telescope

2pm

3

Dr Stuart Clark

Do we need a new theory of gravity?

3.30pm

4

Nik Szymanek

Guide to CCD imaging

Saturday 18 May 9.30am

5

Dr Chris Lintott

Beyond Galaxy Zoo – amateur astronomy on a cloudy night

11.15am

6

Dr Stuart Clark

The day without yesterday

12.30pm

7

Jerry Stone

Life in the Universe

2pm

8

Nik Szymanek

Photographing the night sky

3.30pm

9

Ray Wilkinson

Rocket propulsion

Dr Stuart Clark

Dr Chris Lintott

Dr Stuart Clark writes the Guardian science blog Across the Universe and acts as astronomy consultant for New Scientist. He’s written many books during the past two decades, including a trilogy of novels about astronomy for Birlinn Polygon: The Sky’s Dark Labyrinth (2011), The Sensorium of God (2012) and The Day Without Yesterday (2013). Stuart’s articles have been published widely in newspapers, magazines and online.

Best known as co-presenter for the past decade on the BBC’s The Sky at Night, Dr Chris Lintott is also a researcher at the University of Oxford specialising in galaxy formation and evolution. He is also involved in the development of citizen science, leading to him receiving the Kohn Award for Public Engagement from the Royal Society in 2011. Chris co-authored two books with Patrick Moore and Queen guitarist Brian May, most recently The Cosmic Tourist: Visit the 100 Most Awe-Inspiring Places in the Universe.

Friday 17 May at 2pm 3 Do we need a new theory of gravity? Saturday 18 May at 11.15am 6 The day without yesterday

Saturday 18 May at 9.30am 5 Beyond Galaxy Zoo – amateur astronomy on a cloudy night

Buy your tickets online at www.international-astronomy-show.com/ticket-sales

Jerry Stone

Nik Szymanek

Jerry Stone has given lectures on space since 1969 and has held public exhibitions since 1975. In the 1980s he was on the curatorial staff at the Science Museum, where he covered the astronomy, space and exploration collections, including the Apollo 10 spacecraft. He is a fellow of the British Interplanetary Society and the Royal Astronomical Society, and a director of the Mars Society UK. He speaks all over the UK and abroad.

Nik Szymanek has been imaging the sky since 1985 using film, digital and CCD cameras. He has appeared on the BBC’s The Sky at Night TV programme and has written for astronomy magazines including Astronomy and Sky & Telescope. Nik received the Astronomical Society of the Pacific’s amateur achievement award in 2004 and is a visiting research fellow at the University of Hertfordshire’s Centre for Astrophysics Research.

Friday 17 May at 9.30am 1 Let’s go to Mars!

Friday 17 May at 3.30pm 4 Guide to CCD imaging

Saturday 18 May at 12.30pm 7 Life in the Universe

Saturday 18 May at 2pm 8 Photographing the night sky

Olivier Thizy

Ray Wilkinson

In the 1990s, Olivier Thizy bought himself an 8-inch equatorial telescope and a CCD camera; he mixed deep-sky imaging with photometry work on variable stars and asteroid light curves. He moved into spectroscopy to broaden his spectrum of tools to study the stars and participated in the development of the Lhires III high-resolution spectrograph. In 2006, he co-founded Shelyak Instruments, which now produces a full range of spectrographs specially designed for astronomy.

Ray Wilkinson is the aerospace group leader at the University of Hertfordshire. He teaches a number of aerospace subjects, including rocket propulsion. Students from the university have built and tested a rocket sled that reached over 1,900km/h in one-third of a second, and constructed a rocketpowered sports car in only five weeks. Ray has been involved in a variety of rocket-related TV features for programmes including Bang Goes the Theory, Scrapheap Challenge, Mission Implausible and Beat the Ancestors.

Friday 17 May at 11.15am 2 Spectroscopy with a very small telescope

Saturday 18 May at 3.30pm 9 Rocket propulsion

Buy your tickets online at www.international-astronomy-show.com/ticket-sales