BBC Sky at Night 2013-04

SOUTH POLE SPECIAL: ASTRONOMY IN ANTARCTICA

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SATURN The only guide you need to observe and image the Ringed Planet PLUS

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Green beans in deep space

The far-off galaxies with a curious glow

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ALSO IN THIS ISSUE Our brand new binocular sky tour

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How to pick out this month’s lunar eclipse APRIL 2013 #95 www.skyatnightmagazine.com

LETTER FROM THE EDITOR APRIL 03

Welcome

This month’s contributors include... SAMANTHA CRIMMIN

Saturn is at opposition in April – there’s no better time to observe it

ASTROPHOTOGRAPHER

S

aturn has slowly been moving into the early evening skies this year, and this month’s opposition makes it prime time for HAZEL MUIR observing the Ringed SCIENCE WRITER Planet. With its ring Newshound Hazel gives system beautifully angled and a following of us the latest moons, Saturn is a target not to be missed, so on the take this opportunity to view the planet at its meteor that best since being last on show in summer 2012. exploded over Russia in February, rare supernovae Find out how best to see it on page 32. Binoculars also reveal the wonders of the and more on page 11. Ringed Planet, but that’s not all you can see GOVERT SCHILLING with them, as we reveal in a new regular ASTRONOMY AUTHOR Sky Guide section starting this month, the Govert reports Binocular tour. Stephen Tonkin is your guide on the to six of the best sights visible each month unique and all you need is a pair of medium-sized astronomy experiments that can only binoculars. Join his adventures on page 58. That’s not the only change you’ll see in be performed from the this issue: from page 78, you’ll find our new South Pole on page 65. seven-page Skills section. It’s the place to go STEPHEN TONKIN for practical observing techniques and BINOCULAR OBSERVER knowledge, whatever your level of experience. You don’t need a scope Inside, you’ll find refreshed familiars as well to appreciate as a new section, The guide. the beauty of Onto the features: science writer Govert the night Schilling visited the South Pole late last year skies – Stephen picks out in austral summer to investigate astronomical the month’s best binocular research. His report from the bottom of the sights on page 58. Samantha’s best images and top tips, sent via satellite from the Antarctic, are in our South Pole gallery on page 72.

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world is on page 65 and we find out just how dark Antarctic winter skies can be in a gallery of stunning South Pole astrophotos on page 72. Turning to skies closer to home, features editor Will Gater examines the state of light pollution in the UK on page 40 – food for thought during Dark Skies Week, which runs from 5-11 April. Enjoy the issue!

Chris Bramley Editor

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In the magazine ON THE COVER 32

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NEW TO ASTRONOMY? See The guide on page 78 and our online glossary at www.skyatnightmagazine.com/dictionary

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SPECTACULAR SATURN

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EYES ON ANTARCTIC SKIES

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40 106 16 58 62

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FEATURES

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06 Eye on the sky

11 Bulletin

The latest astronomy and space news.

80 How to

32 Spectacular Saturn

18 What’s on

Set up a dual imaging system, part 2.

The latest stunning space images.

78 The guide Picking the right accessories.

Prepare for opposition with our ultimate guide, packed with charts, observing checklists and more.

Astronomy events from around the UK.

83 Sketching

40 Light revolution

20 Sky at Night diary

85 Scope doctor

Your backstage pass to the TV show.

Our special report examines how changes to streetlighting and council initiatives could affect the UK’s night skies.

62 Rise of the Newtonian

The origins of the most famous reflector design, beloved by amateur astronomers worldwide.

65 Astronomy in Antarctica

We explore the many and varied science experiments that are only possible on this frozen continent.

72 Eyes on Antarctic skies

We asked three astro imagers in Antarctica to send us their best shots – the results are simply stunning.

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Your letters, emails and tweets.

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28 Hotshots

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47 THE SKY IN APRIL 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…

Lunar crater Albategnius. We solve your equipment woes.

87 Lost in space The trials of a novice astronomer.

89 Reviews

First light 90 iOptron Smart EQ Go-To mount. 94 Revelation 25x100 binoculars. 98 StarTools software. 102 Books 104 Gear

106 What I really want to know is…

What makes a green bean galaxy glow?

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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

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Cosmic

collaborators Hubble data has been combined with groundbased observations to reveal a galactic maelstrom

NASA/ESA/THE HUBBLE HERITAGE TEAM (STSCI/AURA)/R GENDLER

HUBBLE SPACE TELESCOPE, 5 FEBRUARY 2013 You could easily mistake this stunning image of spiral galaxy M106 for the work of an artist’s brush, but the subtle hues in the arms and hazy glow at the centre are all the products of real photographs. This impressive creation is the result of a partnership between amateur and professional astronomers, a montage created by acclaimed astrophotographer Robert Gendler. He made this image by combining data from the Hubble Space Telescope and ground-based observations from fellow astrophotographer Jay GaBany with his own. Located 23.5 million lightyears from Earth in the constellation of Canes Venatici, this vast galaxy is over 40,000 lightyears in diameter. Although a spiral like our own Milky Way, the centre of M106 is far more violent, with a supermassive black hole so powerful it has begun to suck part of the galaxy in to it.

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 An emerald basin MARS RECONNAISSANCE ORBITER, 30 JANUARY 2013 NASA’s Mars Reconnaissance Orbiter snapped this infrared image showing the edge of a young impact crater, about 5km wide, using its HiRISE camera. The northern slope of the crater is a blue-green colour, suggesting the presence of minerals commonly found in lava, while the yellow area is typical of dust expelled during an impact.

A Venusian adventure VENUS EXPRESS 21 JANUARY 2013 Venus’s terminator separates day and night in this atmospheric new image from ESA’s Venus Express spacecraft. The photograph is a screenshot from a new animation that shows the spacecraft undertaking a single orbit of the planet.

 Drilling for victory MARS SCIENCE LABORATORY, 28 JANUARY 2013 NASA’s Curiosity rover uses one of its hazard avoidance cameras to capture final preparations before the percussion drill, located at the end of the rover’s robotic arm, breached the rocky Martian surface for the first time. Drilling began in Gale Crater on 8 February.

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The fire that burns cold HERSCHEL SPACE OBSERVATORY, 28 JANUARY 2013 Although fiery in appearance, this infrared image of the Andromeda Galaxy from ESA’s Herschel Space Observatory actually shows bands of newly forming cool stars – just a few degrees above absolute zero. The blue region in the centre is the galaxy’s warmer central bulge.

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NASA/JPL-CALTECH, ESA/HERSCHEL/PACS & SPIRE CONSORTIUM/O. KRAUSE/HSC/H. LINZ

NASA/JPL/UNIVERSITY OF ARIZONA, EESA/MPS/DLR/IDA, M PÉREZ-AYÚCAR & C WILSON,

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BULLETIN APRIL 11

Bulletin The latest astronomy and space news written by Hazel Muir

PLUS

CUTTING EDGE

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

14 16

Comment

by Chris Lintott

A car dashboard camera cought the moment the fireball blazed across the sky

Spectacular meteor rattles Russia

RIA NOVOSTI/SCIENCE PHOTO LIBRARY X 2

The exploding space rock damaged buildings and injured hundreds A DRAMATIC METEOR fireball occurred over the Chelyabinsk region of Russia’s Ural Mountains on 15 February. Entering Earth’s atmosphere at about 65,000km/h, the meteor became brighter than the Sun before exploding. Shock waves damaged numerous buildings, shattering windows and injuring around 1,000 people. Infrasound stations around the world recorded disturbances from the meteor and allowed scientists to estimate the rock’s size. They calculate that it was a whopping 17m wide and had a mass of roughly 10,000 tonnes. “We would expect an event of this magnitude to occur once every 100 years on average,” says Paul Chodas from NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory in California. “When you have a fireball of this size, we would expect a large number of meteorites

One meteorite fragment left this 6m hole in a frozen lake; more fragments, 0.5-1cm wide, were found nearby

to reach the surface and in this case there were probably some large ones.” A large chunk of the meteorite seems to have punched through the surface of a frozen lake, leaving a 6m hole in the ice. Scientists discovered dozens of small fragments of the meteorite in the same area, and provisional analysis suggests they are stony meteorites that contain about 10 per cent iron. Several hours later, an asteroid 50m wide passed within 27,700km of Earth – the closest approach on record for a rock this big; however there was no connection between the asteroid and the meteor strike, as the two had completely different trajectories. > See Comment, right

This dramatic event is probably the most spectacular since the legendary 1908 Tunguska impact, which flattened around 80 million trees over an area of more than 2,100 square kilometres. So why does it always seem to be poor old Siberia that gets hit? It’s partly that there are people around to notice; seismographs and the network designed to monitor nuclear tests, both of which recorded the recent impact, tell us that large events happen more frequently than you might think. The reason we don’t hear about them is because when they occur over the ocean – and bear in mind that most of Earth’s surface, a little more than 70 per cent, is ocean – no one pays any attention. Siberia is also a large target, far larger than Europe. However, its recent role as a bullseye shouldn’t allow the rest of us to relax. If the meteor had swung by a few hours earlier, it might well have scored a direct hit on Europe. CHRIS LINTOTT presents The Sky at Night on BBC TV

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Rare supernova puzzles astronomers

X-RAY: NASA/CXC/MIT/L.LOPEZ ET AL/INFRARED: PALOMAR/RADIO: NSF/NRAO/VLA, ESO/RADIO: NRAO/AUI/NSF/GBT/VLA/DYER/MADDALENA & CORNWELL/X-RAY: CHANDRA X-RAY OBSERVATORY/NASA/CXC/RUTGERS/G. CASSAM-CHENAÏ/J. HUGHES ET AL/VISIBLE LIGHT: 0.9-METRE CURTIS SCHMIDT OPTICAL TELESCOPE/NOAO/AURA/NSF/CTIO/MIDDLEBURY COLLEGE/F. WINKLER AND DIGITIZED SKY SURVEY, ALEJANDRO BENITEZ LLAMBAY X 2, NASA/JPL-CALTECH/MSSS, DSI

Odd explosion may have created the youngest black hole in our Galaxy

News in brief YOUNG STELLAR DUO PUT ON A STROBE SHOW

NASA’s Spitzer and Hubble Space Telescopes have revealed a pair of newborn stars shrouded in dust – shown below – which are regularly emitting bright flashes of light every 25.34 days. Astronomers think the flashes are due to material suddenly being dumped onto the growing stars each time they get close to each other in their orbit, unleashing a blast of radiation. No one has seen such regular, bright flashes from young stars before. “The large brightness variations with a precise period are very difficult to explain,” says team leader James Muzerolle of the Space Telescope Science Institute in Maryland.

A nascent black hole could be lurking in this X-ray, infrared and radio composite of the unusual supernova remnant

A STRANGELY ASYMMETRIC supernova remnant may contain the most recent black hole to have formed in the Milky Way. The remnant, called W49B, lies about 26,000 lightyears away. It is thought to have been created in a rare type of explosion in which the original star ejected jets of matter from its poles of rotation at enormous speeds. Supernova explosions are usually fairly symmetrical, with the stellar atmosphere blasting away evenly in all directions. But W49B is curiously elongated and it’s this that hints that the star could have suffered an unusual demise. Now a team of astronomers have confirmed this theory by analysing observations from NASA’s Chandra X-ray Observatory. They showed that the distribution of elements such as sulphur, silicon and iron in the remnant matched theoretical predictions for an asymmetric explosion. “W49B is the first of its kind to be discovered in our Galaxy,” says team leader Laura Lopez of the Massachusetts Institute of Technology (MIT). skyatnightmagazine.com 2013

“It appears its parent star ended its life in a way that most others don’t.” Why the explosion was asymmetrical is not absolutely clear. But it is hoped that W49B will be useful for detailed studies of the aftermath of such explosions because it’s relatively nearby. Astronomers are also intrigued by what lurks at the remnant’s centre. During a supernova explosion, a massive star’s core usually collapses to form a superdense ‘neutron star’, which can be detected in X-rays. But Lopez’s team did not find a neutron star in W49B, which suggests the star’s core collapsed completely into a black hole with such strong gravity that nothing – not even light – can escape from it. “It’s a bit circumstantial, but we have intriguing evidence the supernova also created a black hole,” says Daniel Castro, also from MIT. “If that is the case, we have a rare opportunity to study a supernova responsible for creating a young black hole.” www.nasa.gov/chandra

SATURN STORM CHOKES ON ITS OWN TAIL

A violent thunderstorm on Saturn churned around the entire planet before encountering its own tail and sputtering out, NASA’s Cassini spacecraft has shown. “Even the giant storms on Jupiter don’t consume themselves like this, which goes to show that nature can play many aweinspiring variations on a theme and surprise us again and again,” says Andrew Ingersoll from the California Institute of Technology in Pasadena. His team has completed a detailed analysis of the storm, which began in December 2010.

BULLETIN APRIL 13

MEDIEVAL SUPERNOVA SEEDS COSMIC RAYS News in brief A STUDY OF a supernova witnessed in medieval times has established it as a source of cosmic rays, high-energy particles that bombard our atmosphere. It has long been suspected that shock waves in supernova remnants accelerate cosmic rays to huge energies. Now astronomers have confirmed this after using the Very Large Telescope in Chile to study the remnant of a supernova recorded in 1006, catalogued as SN 1006. They discovered highenergy protons in the shock region where material from the supernova explosion ploughs into interstellar gas. These protons probably act as ‘seed particles’ that help to generate cosmic rays. “This is the first time we have been able to take a detailed look at what’s happening in a supernova shock front,” says Sladjana Nikoli from the Max Planck Institute for Astronomy in Heidelberg, Germany. www.eso.org/paranal

CURIOSITY DRILLS ROCK SAMPLE

Astronomers analysed the shock front, inset, of SN 1006

Cosmic web blamed for dwarf shortage

NASA’s Curiosity rover has, for the first time, used a drill on its robotic arm to bore into bedrock on Mars and collect a small sample of material. Curiosity’s analysis of the rock could reveal evidence about the Martian environment in ancient times, when water is thought to have flowed on the surface in the area it is exploring. “The most advanced planetary robot ever designed is now a fully operating analytical laboratory,” says John Grunsfeld from NASA headquarters, Washington DC.

Large-scale structures in the Universe rob small galaxies of their gas The cosmic web strips gas from a dwarf galaxy, inset, in this simulation – leaving them too small for us to detect

AN EFFECT CALLED ‘cosmic web stripping’ could explain a long-standing mystery – why are there so few dwarf galaxies in the Universe? On large scales, galaxies and matter clump into an intricate network of filaments and voids known as the cosmic web. Computer simulations of how this structure evolved predict that our cosmic neighbourhood should contain a vast number of dwarf galaxies much smaller than the Milky Way. Yet only a handful of these galaxies are observed in our local Universe. Now a team led by Alejandro

Benítez-Llambay from the National University of Córdoba in Argentina has explained this using a computer analysis of the positions and speeds of galaxies up to tens of millions of lightyears away. The results suggest that some dwarf galaxies move so fast that the cosmic web strips off their gas. “Even the weakest membranes of the cosmic web can rip off their gas,” says Benítez-Llambay. Without a large gas supply to form new stars, these dwarf galaxies would simply remain too small and faint to see. www.unc.edu.ar

SPACECRAFT FLEET TO PROBE ASTEROIDS

Virginia-based Deep Space Industries has announced plans to launch a fleet of spacecraft to study asteroids from 2015. The ultimate goal is to find ways to mine asteroids for materials useful for space technologies. The ‘FireFly’ spacecraft will weigh only about 25kg. “This is the first commercial campaign to explore small asteroids that pass by Earth,” says company chairman Rick Tumlinson. “Using low-cost technologies, we will do things that would have been impossible just a few years ago.”

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CUTTING EDGE

Our experts examine the hottest new research

Revelations from runaway stars A new way of studying stars could help to end the debate over the structure of our Galaxy WORDS: CHRIS LINTOTT This is what we think our Galaxy looks like, but it’s hard to be sure from within it

This sounds promising, but the best data available at the moment isn’t quite up to the job. It comes from ESA’s Hipparcos satellite, which recorded highly precise position and velocity measurements for more than 100,000 stars (along with less precise measurements for another two million). Despite the size of Hipparcos’s legacy, only 50 or so stars suitable for this sort of analysis were found – not enough to do the job.

MARK GARLICK/SCIENCE PHOTO LIBRARY

O

ne recurring theme of this column has been the difficulty of viewing the structure of our own Galaxy. It’s almost maddening that the very thing that makes the Milky Way of particular interest – our position in it – makes it so hard to study. Nowhere is this seen more clearly than in the ongoing argument about the Milky Way’s spiral arms; while there is something of a consensus settling on a four spiral arm structure, some scientists, such as the University of Sao Paulo’s Jacques Lepine, have suggested something weirder – a structure of squarer spiral arms that would make the Milky Way something rather special. To resolve this confusion, a paper by a pair of University of Hertfordshire astronomers suggests making use of special stars within our (potentially) special galaxy. Most star formation within a spiral galaxy takes place within the spiral arms. This behaviour gives the arms their distinctive blue colour in optical images – they are lit up by bright blue stars, stars that are so massive that they will not hang around for long. To determine the position of the spiral arms and to record how they have changed over time, all we need to do is to track each star back to its birthplace. This has been tried for single stars before, but among the hustle and bustle of the Milky Way’s disc it’s a little too chaotic to do easily. Instead, the authors look at an unusual population of runaway stars that exist above the disc itself. They are particularly suitable because their position makes them easier to see – they are moving quickly, so have travelled a long way from their nurseries – allowing us to trace spiral arms far from the solar neighbourhood. skyatnightmagazine.com 2013

“To find out how a spiral arm has changed over time, all we need to do is to track each star back to its birthplace”

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

All is not lost, however. European astronomers are looking forward to the launch of Gaia, a successor to Hipparcos, later this year. Relying, like its predecessor, on careful measurement of parallaxes – the apparent shift in position of a star due to Earth’s movement around the Sun – Gaia will provide ridiculously accurate positions for objects brighter than mag. +15.0. The accuracy of their positions will be 24 microarcseconds – the width of a human hair 1,000km away. This data will enable a host of scientific projects, ranging from studies of stellar evolution through to the detection of exoplanets and probing the dark matter distribution of the Milky Way. Thanks to this paper, we can now confidently expect that it will also shed light on the spiral structure of our Galaxy; let’s hope for a successful launch.

CHRIS LINTOTT was reading… High Galactic latitude runaway stars as tracers of the spiral arms by H D V Silva and R Napiwotzki. Read it online at http://arxiv.org/abs/1302.0761

BULLETIN APRIL 15

News in brief

Alien ‘Earth’ may lurk in our backyard Habitable worlds could circle the nearest red dwarfs

A team of astronomers in Spain have announced that ESA’s Gaia spacecraft, due for launch this year, is likely to find many ultra-cool dwarf stars, ones that have a surface temperature below about 2,200ºC. Gaia will conduct a census of roughly a billion stars in our Galaxy, charting their positions, distances, speeds and variations in brightness with unprecedented accuracy. The team’s analysis has shown that the spacecraft should detect tens of ultra-cool dwarfs in the process, revealing their temperatures and surface gravity. Because these stars are among the most ancient objects in the Milky Way, studies of them should clarify our Galaxy’s early chemical composition.

STILL NO WORD

Fewer than one in a million stars in our Galaxy host alien civilisations advanced enough to transmit signals detectable on Earth. University of California, Berkeley scientists came to this stunning conclusion after failing to detect alien transmissions using the 100m Green Bank (radio) Telescope in Virginia, below.

Around six per cent of red dwarfs, the most common stars in the Milky Way, could possess an Earth-sized world

for Astrophysics in Massachusetts. “Now we realise another Earth is probably in our own backyard, waiting to be spotted.” www.nasa.gov/kepler

VENUS SPROUTS A COMET-LIKE TAIL

Venus’s ‘tail’ appears during periods of weak solar wind

Looking back

ESA, PETER BASSETT/SCIENCE PHOTO LIBRARY, DAVID A. AGUILAR (CFA), ESA/WEI ET AL. (2012), RIA NOVOSTI/SCIENCE PHOTO LIBRARY

GAIA PREPARES TO HUNT ULTRACOOL DWARFS

THE CLOSEST EARTH-like planet to us could only be around 13 lightyears away, a study has suggested. Astronomers reached this conclusion after studying observations from NASA’s Kepler space telescope, which suggest that six per cent of red dwarf stars have habitable, Earth-sized worlds. Red dwarfs are the most common stars in our Galaxy and make up around 75 per cent of the stars closest to our Solar System. “We thought we would have to search vast distances to find an Earth-like planet,” says team leader Courtney Dressing from the Harvard-Smithsonian Center

ESA’S VENUS EXPRESS spacecraft has revealed that when the solar wind is weak the planet’s ionosphere balloons out like a comet’s tail. Venus’s ionosphere – a region of electrically charged gas high in a planet’s atmosphere – is shaped by the solar wind streaming out from the Sun. During an unusually calm period of solar wind activity, Venus Express showed that the ionosphere forms a long night-side tail. “It stretched at least two Venus radii into space,” says Yong Wei from the Max Planck Institute for Solar System Research in Germany. www.esa.int/venusexpress

The Sky at Night April 1961 On 24 April 1961, The Sky at Night celebrated the stunning achievement of Soviet cosmonaut Yuri Gagarin earlier that month, when he became the first man in space and completed an orbit of Earth in the spacecraft Vostok 1. Patrick Moore predicted that it would only be a matter of time before people walked on the lunar surface. “It’s quite on the

cards that the first explorers who really reach the Moon, as they will do in the foreseeable future, are in for a great many surprises,” he said. But he quashed any possibility of carbon-based animal life existing on the airless, waterless Moon, and predicted that alternative forms of life, or primitive plants, were unlikely.

t is one Gagarin’s orbi ilestones m t ea gr e th of ation in space explor In time, he was proven correct on both counts – men first walked on the Moon in July 1969 and they found it to be completely lifeless.

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CUTTING EDGE

Our experts examine the hottest new research

We need a Moon base to explore the stars Space travel is challenging and perilous, but our satellite could be the perfect training ground WORDS: LEWIS DARTNELL A lunar training base could also help us to develop techniques to colonise new worlds

such as a medical emergency, it’s virtually impossible to get back to civilisation due to the weather – whereas the Moon is just a three-day flight home. But the South Pole doesn’t recreate the microgravity conditions and so is not a good test site for biological effects. On the other hand, the International Space Station offers weightlessness, as well as an internal architecture more similar to any interplanetary

THINKSTOCK

S

pace is a pretty unforgiving and hostile place to travel through. Discounting the chance of a catastrophe, like a micrometeorite impact depressurising your vessel, there are a number of hazards inherent to the environment within the spacecraft itself. The human body attempts to remodel itself to the microgravity, causing core support muscles to dwindle; your heart deteriorates; even your bones begin to weaken. These are just the effects astronauts are aware of as soon as they return to Earth. Nandu Goswami and colleagues from the Medical University of Graz have put together a good case for going back to the Moon to overcome these concerns – and many others. Astronauts also experience psychological difficulties from being cooped up in a spacecraft with the same small bunch of people day in, day out. And though the view out of the window from low Earth orbit may be stunning, combating sensory deprivation and keeping yourself engaged can be a real struggle. The crew of the Earth-based Mars500 experiment, for example, found they were listless and slept badly for most of its duration. All of these issues need to be addressed if future long-term space missions – a human visit to Mars, or a nearby asteroid to investigate the mining potential, perhaps – are to be successful. Efforts to understand and so prevent these issues are based on studies in situations similar to interplanetary space missions. For example, staff overwintering in Antarctic research bases provide a good insight into the psychological factors – in fact, in some ways they are in a far more remote and isolated situation than even on the Moon. If anything were to go wrong in the winter months, skyatnightmagazine.com 2013

“The Moon is an invaluable test site for all of the necessary technologies needed to keep astronauts healthy”

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

spacecraft, but is still shielded from the full cosmic radiation by Earth’s magnetic field. Goswami et al argue that the Moon is a “high-fidelity long-duration space exploration analogue”, which to the rest of us means: a good place to practice long space missions. A Moon base, they say, offers the perfect opportunity for us to learn about the physiological and psychological issues of an interplanetary mission, while keeping relatively close to Earth in case of an emergency. Thus, the Moon offers a great staging post for further space exploration, but is also an invaluable test site for all of the necessary technologies needed to keep astronauts healthy, both in body and mind. And it’s not just the medical element. A Moon base would also allow us to develop other crucial skills for colonising outer space, such as constructing habitats and growing food.

LEWIS DARTNELL was reading… Using the Moon as a high-fidelity analogue environment to study biological and behavioral effects of long-duration space exploration by N Goswami et al. Read it online at http://dx.doi.org/10.1016/j.pss.2012.07.030

BULLETIN APRIL 17

Super-Earths aren’t all they seem

News in brief

Thick atmospheres may make these worlds more akin to little Neptunes

COSMIC-RAY BALLOON BREAKS FLIGHT RECORD

Famous super-Earth 55 Cancri e could be less like Earth than previously thought

SO-CALLED ‘SUPER-EARTH’ planets orbiting stars beyond the Sun may turn out to be far less Earth-like than their name suggests. A new study suggests that rather than being rocky worlds with potentially habitable surfaces, they are more like miniature Neptunes, smothered by vast envelopes of hydrogen-rich gas. Hundreds of possible super-Earth candidates have been identified by NASA’s Kepler spacecraft, launched in March 2009. Theoretical models suggest many planets form with thick hydrogen atmospheres. On Earth, heating from the Sun and low gravity meant that much of this atmosphere escaped into space. But the jury was out on how much gas would be retained by super-Earths, which have stronger gravity. To find out, a team led by Helmut Lammer from the Space Research Institute in Graz, Austria, studied the

properties of seven super-Earths whose masses and sizes are fairly well known. Their calculations suggested that six of the seven planets would retain most of their atmospheric shrouds during the entire lifetime of their parent stars. “Although material in the atmosphere of these planets escapes at a high rate, many of these super-Earths may not get rid of their hydrogen-rich atmospheres,” says Lammer. In that sense, most super-Earths would be more like small Neptunes. All the planets studied move around their stars in hot, close orbits. If they were farther from their stars with hospitable temperatures for life, they would even more efficiently cling onto their thick gas shrouds, making them extremely unlikely to host life as we know it. www.nasa.gov/kepler

NASA/JPL-CALTECH/R. HURT (SSC), ESA–C. CARREAU/NAZÉ ET AL, NASA, ESO/P. BARTHEL

SMOOTH STELLAR WIND

GIANT STARS BLOW GUSTY WINDS ESA’S XMM-NEWTON SPACECRAFT has shown that the fierce winds blowing out from massive stars are unexpectedly clumpy, with material fragmenting into countless sections that continually collide. Analysis by Yaël Nazé from the University of Liège in Belgium revealed clumps in the wind streaming out from the massive naked-eye star Zeta Puppis. “New XMM-Newton data reveal hundreds of thousands of individual hot and cool pieces,” says Nazé. His team also discovered large, possibly spiral structures in the wind, but new models will be needed to explain the observations. http://xmm.esac.esa.int

ZETA PUPPIS

A huge NASA science balloon launched in Antarctica in December broke the flight duration record for a balloon of its size, staying aloft for more than 55 days. Super-TIGER’s instruments detected millions of cosmic rays, high-energy particles from deep space.

BLACK HOLES FEED FAST

The giant black holes that lurk in the centres of most galaxies grow faster than expected, a study suggests. Astronomers thought these supermassive black holes mainly grow following galaxy collisions, when large concentrations of gas ‘feed’ the black hole. But now a team led by Victor Debattista from the University of Central Lancashire has analysed black hole masses in different galaxies. They found that mergers alone can’t account for the rapid growth phases of supermassive black holes in spiral galaxies such as M104, below. “It’s no longer possible to argue that black holes in spiral galaxies do not grow efficiently,” says Debattista.

The stellar wind streaming from Zeta Puppis, illustrated here, appears to contain hot (red) and cool (blue) clumps

skyatnightmagazine.com 2013

18 WHAT’S ON APRIL

What’s on

Our pick of the best events from around the UK

MAD about space Spaceport, Liverpool, 27 April, 10am

PICTHKE

Medieval astronomers Clanfield Hall, Waterlooville, 12 April, 7.45pm From Islamic astronomy in Arabia to Hellenistic astronomy and the role of Ptolemy, the medieval era revealed a great deal about our Universe. Hear astronomy and space technology writer Dr Mike Leggett discuss the development of medieval astronomy at the Hampshire Astronomical Group and discover more about this fascinating period in the history of space science. Free for members, £3 for non-members. www.hantsastro.org.uk

60 years of radio astronomy

OF MONTH

University of London, London, 27 April, 2pm Dr Tim O’Brien of the University of Manchester’s Jodrell Bank Observatory looks back at 60 years of radio astronomy in this talk for the Society for Popular Astronomy. As well as considering the advancements made, he will look forward to the future, anticipating the arrival of the Square Kilometre Array, illustrated above, with construction due to begin in 2016. www.popastro.com/meetings/index.php

Liverpool’s docks are preparing for another astronomy extravaganza

THINKSTOCK X 2, SKA ORGANISATION/TDP/DRAO/SWINBURNE ASTRONOMY PRODUCTIONS, © JAMIE COOPER/THE NATURAL HISTORY MUSEUM/LONDON

This month sees the annual Merseyside Astronomy Day (MAD) return for an eighth year. Hosted by Liverpool John Moores University’s Astrophysics Research Institute and Spaceport, where the event is also held, MAD VIII will include interactive displays, simulator rides, virtual wormholes, 3D shows and more. These serve as entertaining asides to the collection of talks scheduled for the event, from astrophysicists including Prof Carole Mundell, Dr Ben Davies

and Dr Chris Davis from Liverpool John Moores University and Dr Ross McLure from the University of Edinburgh. Their lectures will cover subjects ranging from supernovae to the legacy of Hubble, black holes and the early Universe. The talks are free, but the usual prices to enter Spaceport apply – £8 for adults, £4.50 for children and £5.50 for concessions. For more details call 0151 231 2900 or email [email protected]. www.astro.ljmu.ac.uk/MAD

BEHIND THE SCENES THE SKY AT NIGHT IN APRIL and

One, 7 April, around midnight (repeated Two, 13 April, midday)*

Four, 8 April 8pm;

THEY FALL TO EARTH Lucie Green and Chris Lintott visit the Natural History Museum (NHM) in London to look at its meteorite collection and discuss the recent Russian impact. Jon Culshaw goes on a meteorite hunt, and Pete Lawrence and Paul Abel give a beginners’ guide to observing Saturn. The Barwell meteorite, part of NHM’s collection, is the biggest found in Britain

skyatnightmagazine.com 2013

*Check www.radiotimes.com as times may vary

A weekend of discovery University of Oxford, Oxford, 19-21 April, 6pm New Perspectives in Astronomy is a weekend course aimed at serious amateur astronomers keen to familiarise themselves with the cutting edge areas of science. Using images from far-flung space probes and ground-based scopes, you’ll learn what the latest astronomical discoveries mean to our understanding of the cosmos. Tickets start at £120. www.conted.ox.ac.uk/courses/details.php?id=F900-18

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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20

diary The Sky at Night heads to Kielder to hunt for a near-Earth asteroid and check out the results of the Moore Winter Marathon, reports presenter Paul Abel

F

ebruary 15th heralded an event of some minor cosmic significance, scheduled by the machinery of nature. Late that evening, a small piece of Solar System debris with the glamorous name of 2012 DA14 made a close pass of the Earth. Very close in fact. The asteroid passed some 34,000km above us – that’s nearer than the satellites that circle our planet. It was visible in UK skies as a binocular object after 8pm, and with this in mind The Sky at Night set off to the Kielder Observatory in Northumberland to try and film the event, as well as present the results of the Moore Winter Marathon. The asteroid caused quite a stir. I’d already done some radio interviews for BBC Leicester and BBC Bristol discussing its significance, and the

Asteroid 2012 DA14 was a hard spot for Chris North and Lucie

energy (equivalent to 500,000 tonnes of TNT) it was still powerful enough to shatter windows and damage buildings.

BBC, PAUL ABEL X 2

“You wonder how the search for nearEarth objects might be stepped up if the meteor had taken out a large city” reasons why we needn’t run to the hills screaming “We’re doomed!” just yet. More alarmingly, news of a different rock also caused a storm – a large meteor exploded some 15km above the Russian city of Chelyabinsk. Although the atmosphere absorbed much of the skyatnightmagazine.com 2013

It serves as a powerful reminder that our stay on this planet is still very much at the mercy of nature; the Solar System is not always as benign as it appears. You can’t help but wonder how the search for near-Earth objects might be stepped up if the meteor had taken out a large city.

This time, thankfully, it didn’t, but what else is out there?

North by northwest Kielder Observatory is a splendid place, and houses two impressive telescopes. The turret holding the largest, a 0.5m Newtonian reflector, was renamed ‘The Patrick Moore Observatory’ in honour of our late presenter that very afternoon. The observatory is located near Kielder Water and is rather remote. I’d arranged to meet Pete Lawrence for the journey north from Leicester, but thanks to some interesting directions from a local chap (which omitted a T-junction and a right turn), we arrived a little late. Well actually, very late.

>

BEHIND THE SCENES APRIL 21

VICTOR DE SCHWANBERG/SCIENCE PHOTO LIBRARY

Jon takes a breather after unveiling the plaque for the Patrick Moore Observatory

Series producer Jane Fletcher literally grabbed us as we got out of the car and plonked us in front of the cameras, where Lucie Green and Chris Lintott had been patiently waiting to record the opening of the show. After we had filmed the opening we were amazed to see the clouds begin to clear – something almost unheard of on a Sky at Night shoot. The stars of our Galaxy shone forth and it wasn’t long before Kielder’s telescopes were being pointed at some interesting corners of the cosmos. As the skies continued to clear we realised that seeing the asteroid had now moved from theoretical absurdity to being quite likely, and in fact, we realised we’d better start looking for it. By 8.30pm it was well above the horizon and we all began to search for it. A large group of amateurs had collected at Kielder and there were plenty of telescopes and binoculars scanning the sky looking for the elusive chunk of rock. Pete was the first to spot it in his binoculars. I asked him for a reference but the thing was moving too quickly. All he could do was shout out how amazed he was to see it! I grabbed a pair of binoculars and fairly soon – and quite by accident I must admit – I stumbled across it: a faint, star-like point moving rapidly towards Ursa Major. Shortly after I heard Chris Lintott triumphantly declare that he had found it, followed quickly by Jon Culshaw, who had joined us for filming and also unveiled the plaque dedicating the Patrick Moore Observatory. Lucie managed to catch sight of it in a telescope set up by one of the amateurs, but the asteroid stubbornly eluded Chris North. We were all surprised by how quickly 2012 DA14 was moving. I’d hoped to make a drawing showing its change in position over time, but it was travelling far too quickly for that. By 9.30pm it would be near the star Alioth in Ursa Major, but by now it was fading fast. I lost it sometime after this, but Chris North finally managed to catch a glimpse of the little space rock just before it passed into obscurity once

more. We were all elated to have seen it – Jon in particular, who had kept the faith alive all evening by insisting nature would

After we had closed the show, a girl and her family came up to ask Lucie how you go about becoming an

“We were amazed to see the clouds begin to clear – something almost unheard of on a Sky at Night shoot” deliver for us. For me, it’s the most memorable Sky at Night event to date.

Winter’s bounty We retired to a nearby B&B to prepare for the next day’s shoot, which would focus on the Moore Winter Marathon. Chris North had a brainwave: why not get all the people who took part in the Moore Winter Marathon to put up the objects they saw on a big star chart. Our assistant producer Keaton Stone had worked hard grabbing suitable pictures of all the objects so they could be assembled into a large map. We would film this with Chris Lintott and Lucie talking us through the objects, and Jon reading out some of the viewer’s comments. It was great to watch our viewers putting up the objects they had seen and this for me is one of the reasons The Sky at Night is such a success – how many other shows actively seek out the audience and make them part of the show? At the end of it Jon remarked that we had made the first Sky at Night advent calendar!

astronomer. Young amateur Daniel Monk promised to make a start on visual observing while others wanted advice on starting in astrophotography. It seemed we had drawn lots of new people to astronomy at Kielder that day – the Moore Winter Marathon being a great way to make a start on exploring the Universe, and The Sky at Night doing what it does best. New stars in the making, I’m sure. S

THE SKY AT NIGHT IN APRIL One, 7 April, around midnight (repeated Four, 8 April 8pm; and Two, 13 April, midday)*

THEY FALL TO EARTH Lucie Green and Chris Lintott visit the Natural History Museum in London to look at its meteorite collection. Jon Culshaw goes on a meteorite hunt, and Pete Lawrence and Paul Abel give a beginners’ guide to observing Saturn. *Check www.radiotimes.com as times may vary

skyatnightmagazine.com 2013

22

Interactive EMAILS • LETTERS • FACEBOOK • TWEETS

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 Stars and Planets. Stargazing with Binoculars by Robin Scagell and David Frydman contains equipment and observing guides, and you’ll be viewing planets in no time with Peter Grego’s Solar System Observer’s Guide.

MESSAGE OF THE MONTH Don’t worry, Mr Lawrence After reading Vincent Whiteman’s excellent article on using smartphones for astrophotography (January issue, page 87) I decided to put his advice to good use. I had already modified a Celestron Travelscope 70 for solar observing by purchasing a full aperture filter and solar finder. I drilled the dew shield and fitted some thumbscrews so that I can be sure the filter won’t dislodge – I’m quite attached to my retinas and would like to remain so! I bought an adaptor as you recommended and I was stunned at the improvement over my earlier attempts at holding the phone. I selected an app called TopCamera, which allows a lot of control over the camera (shutter speed and lots more – I’m still experimenting). I also discovered that the iPhone (iOS5 or greater) allows the shutter to be triggered by pressing the Volume+ button and this also works when using headphones with inline volume controls. In effect, the headphone cable becomes a remote control for the camera shutter and it allows much steadier images. I believe that some other smartphones have this feature too. My images here are straight from the iPhone with no processing at all. It won’t give Pete Lawrence sleepless nights, but it does show what can be done with very modest equipment. The speed and ease allows me to make a quick and accurate record, which I use to make my observation report for the

Raining rocks þ The speedy asteroid was

hard to image, appearing as a streak in this shot

skyatnightmagazine.com 2013

On the day that Russia was unexpectedly bombarded with a rock from space, members of the Norman Lockyer Observatory (NLO) were more prepared for the flyby of asteroid 2012 DA14. Although the skies were partly cloudy at first, by 8.15pm a clear patch appeared and we were able to observe the object with binoculars and also record images of its passing. It was travelling so fast that even 5-second exposures left a trail on each image. “It looks just like a grain of rice” commented one young member of the NLO Space Cadets. This was the closest approach ever predicted for an object of that size and was considerably larger than the rock that hit Russia earlier in the day. These two events

Mark’s setup and, below, two of his smartphone solar shots

BAA Solar Section. Thanks for a very useful article and a wonderful magazine, long may it continue. Mark Tissington, London

Great to hear you’re submitting your solar reports to the BAA, Mark. I’m sure many will find your advice about using headphones as a remote shutter control useful too. – Ed happening within 24 hours must surely serve as a wake-up call to continue the search for potentially hazardous objects out there in space. David Strange, Chairman, Norman Lockyer Observatory

You’re quite right, David, the unexpected appearance of a 17m-wide space rock over Russia shows we must improve our monitoring of near-Earth objects. – Ed

Pleasing gloom In these days of doom and gloom it is pleasing to give good news. Birmingham City Council has started on a programme of replacing street lighting, of which the city has 95,000. They are replacing 41,500 lights in residential streets by

LETTERS APRIL 23

The big debate Have your say at http://twitter.com/ skyatnightmag @skyatnightmag asked: Were you lucky enough to spot asteroid #2012 DA14 on Friday night? What did you think? @csfnorthcott Missed 2012 DA14 but going out tonight to search for galaxies. @scarbastro As usual British weather ruined any chance of #2012 DA14. However, we did enjoy a talk by Paul Money on Messier Marathon. @RockersAndrew Clouded out but have hopes for Comet PANSTARRS unless it turns into totally Pants starrs! @3picklesmith No. Didn’t see it through the cloud and the wine was more interesting! @dumbasslst I was lucky enough... to stare at thick white clouds, all night long. All. Night. Long. Gotta love living in London. @matttheaviator The clouds were out of the way so I followed it for quite a bit. It doesn’t make up for missing the transit of Venus though.

Viewers of the BBC’s The One Show may have seen features editor Will Gater on the programme back in February. Will joined presenter Lucy Siegle and 20 amateur photographers (who, mostly, had never tried astro imaging) in the Brecon Beacons

2015. The new streetlights will be state of the art LEDs, which illuminate the road and pavements very well but have reduced light pollution. There is also the plus side of cutting carbon emissions and reduced energy bills. I am very pleased to see the city I live in going down this path. Will Birmingham be the first city in this country to go dark? I hope so very much and will it stimulate other cities and towns to embark on similar programmes. We will have to wait and see. Alan York, Birmingham

Turn to page 40 to read more about the impact of LED lighting on skyglow from our urban areas. – Ed

East meets west? Having just read the Sky at Night Magazine booklets in the Daily Telegraph, I am somewhat perplexed. I am keen to know why the sky charts show the east and west positions to be opposite the norm. North is usually at 0 º/360 º, east at 90 º, south at 180 º and west at 270 º. Why is east in the 270 º position and west in the 90 º position? If your publication says to look to the east to see a particular star do I look to my normal east at 90 º or to my normal west at 270 º? Please advise – I am confused. Les Wild, Bournemouth

The star chart is a map of the sky above, not of the ground below. So if you’re facing north, holding the

for an evening of astrophotography under dark night skies. As part of the programme Will judged a competition to find the best astro image taken by the photographers during the live show. We’re delighted to publish John Fawcett Wilson’s winning image, a wide-field shot of Orion, here in the magazine. Congratulations John!

map above your head with the word north pointing in the right direction, east will be in the normal (90º) position. Avoid aching arms by holding the chart so the direction you’re facing is at the bottom (it will be upside down if you face north) and the compass points will be positioned normally. – Ed

Following his example The sky was clear on the early evening of 17 January. I was intrigued by features of a lunar crater so got out paper, pencil and torch to sketch it and its surroundings (shown right). The impression was of a ditch inside the crater wall, with two large blocks at one side. The raised, smooth floor had a small crater off-centre. There were several other small craters on the wall. A long sinuous fold ran off over the smooth surface of a mare. It took some searching of lunar maps to identify the crater as Posidonius. Remembering Patrick Moore’s lunar series in Sky at Night Magazine, I thought to leaf through my pile of back issues in the hope of finding Posidonius. What luck! In the January issue (page 63) he covered the very crater, describing the features much better than I could and explaining their significance. Patrick was always there to help amateurs. We skyatnightmagazine.com 2013

24

SPA celebrates 60 years

From our fans on This month, we gave our Facebook fans a guide to observing asteroid 2012 DA14. This is how they got on before and after the historic event. Jonathan Hall Beautiful clear night, already got some images of the Moon. I’m going to try to get a long exposure of it flying through the handle of the Plough. John Iddon Wouldn’t you know it! The sky’s clouded over at just the wrong moment. Neil Walters Clear viewing here tonight in South Wales. Tom Roberts So EXCITING!!! Going to have the 250 EQ6 working tonight. Jilly St John You sure this didn’t explode over Russia this morning? Lol hope I see something! Conor McLennan Cook Was working, completely gutted.

Back in 1953, a group of amateur astronomers decided that not enough was being done for beginners to astronomy. The result was the Junior Astronomical Society. Today it has a different name – the Society for Popular Astronomy – but it’s still going strong, celebrating its 60th anniversary in January with a meeting in London. The original intention was for its last surviving founder member, Sir Patrick Moore, to attend the meeting, but with his death in December 2012 plans were rearranged and instead the meeting heard reminiscences of the great man from a group of his colleagues and guests on The Sky at Night. Chris Lintott reported on various incidents that had taken place over the years of the programme. One early success was the showing of the first-ever pictures of the far side of the Moon, which Patrick had not seen when he went on air. The only warning he got was a voice in his earpiece saying ‘First pictures of the far side of the Moon coming in 3... 2... 1... good luck! Fortunately, Patrick’s knowledge of the Moon enabled him to recognise features straight away. David A Hardy related how he started his career in 1954 by illustrating a book by Patrick, while John Zarnecki gave a flavour of what it was like to appear on The Sky at Night. Paul Abel looked at Patrick’s observing work, including how the Great Meudon Refractor caught fire as he used it! Ian Morison reminded the meeting of another of Patrick’s legacies, the Caldwell Catalogue, while in a

will miss him but trust that others will continue to follow his magnificent example. Dermot Stewart, Canterbury

You’ll be pleased to hear that Pete Lawrence is continuing to highlight fascinating lunar features in The Sky Guide each month, Dermot. – Ed

The right kind of pedantry The Big Questions series was enthralling. In Dr Mike Evans’s piece ‘Where was the Big Bang’ (January issue, page 81), his use of analogy certainly helped amateurs like me grasp most of the concepts. But there is one aspect that still bothers me. Maybe I am just a rather dumb pedant, but my understanding of an infinitesimally small point – the singularity – is that it has no structure. If it does have structure then it is not actually an infinitesimally small point. If the Big Bang ever was such a thing, then would this require something to happen as it came into existence to provide the structure that goes on to expand into the cosmos? And if so, what forces were at work? David Tart, via email

Glad you enjoyed The Big Questions. There are two separate aspects to your query, both of which are still areas of research. The development of structure from an initially featureless state requires some randomness in the laws of nature – an idea that remains difficult to interpret. The second aspect of your question is about the existence of a singularity at the beginning of the skyatnightmagazine.com 2013

Þ 60 years on and the SPA is still going strong

Þ Friends and colleagues shared their anecdotes recorded contribution Peter Cattermole described his lifelong friendship with Patrick. Following the break, Robin Scagell and Derek WardThompson looked back at 60 years of both the society and astronomy. Videos of the meeting can be viewed on the SPA website at www.popastro.com/meetings. Robin Scagell, SPA vice-president

Universe. However tiny the early Universe was, it’s easy to imagine it being magnified into the present-day structure. But a tiny thing is fundamentally different from a zero-size point. No matter how much you magnify a point, it remains zero-size. So no theory can describe the universe smoothly developing from a point into a thing with size, and that’s a big unsolved problem for theorists. Your query is far from dumb; it’s exactly the right kind of pedantry! – Mike Evans

One of a kind I felt a great loss in hearing that Sir Patrick Moore had died. He inspired my interest in astronomy (that and the Apollo Moon landings). I became interested around 1969 or so, when I was about eight years old. Of course, when I was a child, The Sky At Night was broadcast too late for me to watch, but once I was old enough to do so, I faithfully watched virtually every programme. I envied his big telescopes but it was many years before I could get a decent-sized one! I did see him in person a number of times – in 1998, giving a lecture in Sutton; another time he came to my school, long after I had left there as a pupil. I saw him give a concert on the xylophone in the main hall there in 1995. He was a one-off and the world will never see his like again. Gary Walker, Banstead, Surrey

It was nice to hear in February that Kielder Observatory had renamed its largest turret in honour of Patrick. His memory lives on! – Ed

LETTERS APRIL 25

ASTRO CROSSWORD Number 35. 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, Adam Crute, Lewis Dartnell, Glenn Dawes, Alastair Gunn, Keith Hopcroft, Carol Lakomiak, Pete Lawrence, Chris Lintott, Hazel Muir, Kate Oliver, Jeff Parker, Steve Richards, Govert Schilling, Giles Sparrow, 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 1 Jewel of the Southern Sky – a globular cluster or a galaxy remnant? (5,8) 6 How many meteors would you see with clear, dark skies if the radiant of a meteor shower was directly overhead (acronym)? (3) 7 A unicorn chases this hunter across the sky. (5) 8 Comets may have two of these. (4) 10 Colour commonly seen in modest aurorae. (5) 11 Home of the south celestial pole. (6) 14 A meteor can leave a persistent, glowing one of these as it passes through Earth’s atmosphere. (5) 15 Prestigious astronomical society (acronym). (3) 16 A star in the handle of the Plough asterism. (6) 17 NASA’s Glenn Research Center is located in this US state. (4) 18 Brian __ wrote the music for Al Reinert’s documentary about the Apollo missions. (3) 19 The site of the Prime Meridian (acronym). (3) 21 You’ll find this star in the Teapot asterism. (5) 24 Astronomers keep an eye on these space rocks as they can come close to our planet (acronym). (3) 25 Right ascension and declination scales are scribed onto these. (7,6) 28 M101 is known as the ________ Galaxy. (8) 29 The Caldwell catalogue was created by this famous British astronomer (surname). (5) DOWN 1 Another name for one of the large seas on the Moon, caused by a massive asteroid impact. (9,5) 2 The best time to see Mercury is when it is at greatest western (or eastern) __________. (10) 3 Meteor Crater is located in _______. (7) 4 Phenomena produced by gravitational lensing. (8,4)

5 Saturnian moon with hydrocarbon lakes. (5) 9 Incredibly volcanic moon of Jupiter. (2) 10 Famous manufacturer of the 28-inch refractor at the Royal Observatory Greenwich (surname). (5) 12 Famous orbiting solar observatory (acronym). (4) 13 Instrument on the forthcoming James Webb Space Telescope, built in the UK (acronym). (4) 20 Name of Apollo 10’s lunar module. (6) 22 Astro imagers constantly try and reduce this in their pictures of celestial objects. (5) 23 You might use one of these to bring out detail on a planetary disc or when viewing a nebula. (6) 26 Optical aberration seen in some telescopes. (4) 27 Many amateur observatories use a roll-off ____ design. (4)

The solution to this crossword will be published in the May 2013 issue. Astro Crossword number 34 solution

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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.

The publisher, editor and authors accept no responsibility in respect of any products, goods or services that may be advertised or referred to in this issue for any errors, omissions, mis-statements or mistakes in any such advertisements or references.

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Hotshots This month’s pick of your very best astrophotos PHOTO OF THE

MONTH

p The aurora over Thurso Bay GORDON MACKIE THURSO, 20 NOVEMBER 2012 Gordon says: “I wasn’t expecting much of a display with the Kp index only at 2, but as the skies were really clear and there was a low green arc to the north I decided to head for a suitable spot to enjoy the view. To my surprise and delight the arc burst into life and gave a bright dynamic display that lasted a good 30 minutes, providing a truly memorable evening viewing nature’s great light show.” Equipment: Canon EOS 650D DSLR camera, zoom lens set at 29mm Sky at Night Magazine says: “With this year’s anticipated solar maximum all eyes are on the northern skies for signs of the elusive aurora. Gordon’s stunning image captures a truly magnificent display and

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shows that you don’t necessarily have to venture into the Arctic Circle to get a glimpse of this beautiful phenomenon.” About Gordon: “Like so many I became interested in astronomy at an early age after first seeing Sir Patrick Moore on The Sky at Night. This interest remained over the years. Latterly a modest telescope upgrade and the capability of DSLR cameras have allowed me to explore the Universe in more detail than ever before and capture the many wonders visible in the dark skies above the Highlands of Scotland.”

The Crescent Nebula  IAN DUNBAR BRITTANY, FRANCE AUGUST 2012 Ian says: “This picture is composed of 12 hours of 600 second sub-exposures and was taken over three nights at the end of August. It was my first attempt at imaging the region of the Crescent Nebula and I was pleasantly surprised at the amount of nebulosity I managed to capture in the surrounding areas.” Equipment: Modified Canon EOS 450D DSLR camera, William Optics ZS80 FD refractor, EQ6 Pro mount

HOTSHOTS APRIL 29

 Jupiter DENNIS BOON SUFFOLK 23 NOVEMBER 2012 Dennis says: “The first clear night for a couple of weeks and with Jupiter nearing opposition it was a great opportunity for some imaging. I particularly like this shot, showing the Great Red Spot and Red Spot Junior. They were well placed and the equatorial belts showed lots of detail as well.” Equipment: Imaging Source DFK 21AU618.AS CCD camera, Orion Optics OMC200 Maksutov-Cassegrain telescope, TeleVue 2x Powermate

 Mercury, Venus and the Moon at sunrise STEFANO DE ROSA, CASTELNUOVO DON BOSCO, ITALY 11 DECEMBER 2012 Stefano says: “Near the bottom left of the frame, just above the colourful twilight show, is Mercury; Venus is shining left of the Moon’s sunlit crescent.” Equipment: Canon EOS 5D MkII DSLR camera, EF24-105mm L IS USM lens set at 105mm

 Total solar eclipse ROBERT B SLOBINS, QUEENSLAND, AUSTRALIA, 13 NOVEMBER 2012 Robert says: “The seeing at our site was rather poor, but my mission did not require perfection. We were more than grateful that we saw all two minutes and two seconds of totality, whereas most on the windward side of the Great Dividing Range [an Australian mountain range] were lucky to have seen anything at all.” Equipment: Canon EOS 5D DSLR camera, Tamron 300mm lens

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 The Sun in hydrogen alpha JOHN CHUMACK, OHIO, US, 5 DECEMBER 2012 John says: “There is something mesmerising about viewing the Sun in hydrogen-alpha light. From hour to hour you can see sunspots develop, and watch prominences and filaments change. Some of the prominences resemble animals or creatures too! The tremendous amount of detail visible never fails to amaze me.” Equipment: Imaging Source DMK 31AF04 CCD camera, Lunt 60mm/50F hydrogen-alpha solar telescope

The Andromeda Galaxy  JAMES STANNARD, SUFFOLK, 11 NOVEMBER 2012 James says: “I like this wider perspective of the Andromeda Galaxy. This was taken with my little EQ3-2 mount – I hope it brings inspiration to others wanting to take images on a limited budget.” Equipment: Modified Canon EOS 1000D DSLR camera, Canon 200mm L lens, Shoestring Astronomy modified EQ3-2 mount with dual axis motors

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HOTSHOTS APRIL 31

 Kemble’s Cascade BILL MCSORLEY, LEEDS 12 OCTOBER 2012 Bill says: “Kemble’s Cascade is such a simple, beautiful asterism. Its size alone is impressive – even with my relatively widefield telescope and large CCD camera, it needed a three-panel mosaic to capture it all. I particularly like the star colours and the dark dust lanes that have shown through against the backdrop of a very crowded Milky Way.” Equipment: QHY8L cooled one-shot colour CCD camera, Sky-Wacther 150P Newtonian reflector, EQ5 Go-To mount

 The Rosette Nebula TERRY HANCOCK, MICHIGAN, US, OCTOBER AND NOVEMBER 2012 Terry says: “Using 10-minute exposures for RGB, five-minute exposures for the luminance channel and 30-minute exposures for hydrogen alpha, my goal was to go very deep so that I could capture some of the beautiful cosmic sculptures and globules of dark dust in detail.” Equipment: QHY9M monochrome CCD camera, TMB 92SS apo refractor, Paramount GT-1100S mount

 The Milky Way and a meteor LUIS ARGERICH, ARGENTINA, 24 NOVEMBER 2012 Luis says: “This is a shot of the summer Milky Way as seen from the southern hemisphere. The bright nebula at the top is the Eta Carina Nebula; I also captured a meteor and some lightning near the horizon.” Equipment: Canon EOS 60Da DSLR camera, 14mm Bower lens, Vixen Polarie star tracker

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

At opposition this month, Saturn presents an inspirational sight. Pete Lawrence tells you how to get the best views and images

NASA AND THE HUBBLE HERITAGE TEAM (STSCI/AURA)ACKNOWLEDGMENT: R.G. FRENCH (WELLESLEY COLLEGE), J. CUZZI (NASA/AMES), L. DONES (SWRI), AND J. LISSAUER (NASA/AMES)

A

sk an amateur astronomer what got them into astronomy and there’s a good chance that they’ll tell you about their first look at the planet Saturn through a telescope. If you’ve ever done this yourself, you’ll know exactly why, but if you’ve never had this particular pleasure now is a good time to try. If you don’t have a scope of your own, get in touch with your local astronomical society and see if they can help. Saturn’s good at the moment because it’s at opposition, the time when it’s in the opposite part of the sky to the Sun, on 28 April. At opposition, Earth and Saturn are at their closest, so the Ringed Planet looks brighter and bigger than at any other time. As Saturn is naturally a fair distance away, roughly 1,340 million km (9 times farther from the Sun than Earth is) the difference is actually quite modest. At opposition Saturn will shine at mag. +0.3 and will show a globe that appears to be 18 arcseconds across. For a bit of context, by November 2013, when both Earth and Saturn find themselves on opposite sides of the Sun, Saturn will have dimmed to mag. +0.8 with a globe just 15 arcseconds across. To the naked eye Saturn resembles a bright star and can be located by using a real star of similar brightness which lies nearby. First locate the familiar pattern of the Plough. Extend the arc of this asterism’s handle away from the bowl and you will eventually arrive at the bright orange, mag. +0.2 star Arcturus in Boötes. Keep following the arc and you’ll arrive at the bright white, mag. +1.0 star Spica in Virgo. Look for a similarly bright star to the left of Spica and that will be Saturn. Study it carefully and you should see that Saturn is marginally brighter than Spica and appears yellowish in contrast to the white star. >

Jupiter may have clearer belts, but Saturn’s rings are unparalleled

34

SATURN’S FEATURES North Polar Region

Shadow cast by the globe on the rings

Shadow cast by the rings on the globe A Ring (14,600km wide)

Encke Minima (subtle contrast darkening inside the A Ring)

Encke Division (325km wide) Cassini Division (4,700km wide) North Equatorial Belt B Ring (25,500km wide)

Equatorial Zone South Polar Region

C Ring (17,500km wide)

OBSERVING CHECKLIST

DAMIAN PEACH, NASA/JPL-CALTECH/SPACE SCIENCE INSTITUTE X 3, NASA/JPL/STSCI X 2, PETE LAWRENCE X 2

WHITE SPOTS White spots represent storms in Saturn’s atmosphere. In 2011 a huge white storm encircled the planet.

SHADOWS Saturn’s globe casts shadows on the rings and vice-versa. It’s thrilling to watch how these change over time.

BELTS The easiest ones to see are the North and South Equatorial Belts, and the North and South Polar Regions.

> Saturn is in Libra at opposition but crosses into Virgo on 14 May. It then slowly drifts westward toward the mag. +4.2 star Kappa (k) Virginis, passing less than 0.5º from it mid-July. After this the planet switches direction and heads east.

Inside the gas giant Normal binoculars will not show the planet’s rings but may, if held steady, show the largest moon Titan when it’s at its farthest from the planet. Check our moon position chart on page 52 for the best times to look. Using a telescope, the rings start to become visible at around 25x magnification and are quite obvious at 100x. For a full-on Saturn experience, magnifications of 250x and up are recommended. skyatnightmagazine.com 2013

INTENSITY ESTIMATES Use a scale of zero (brightest) to 10 to estimate the relative brightness of parts of the Ringed Planet.

MOONS Eight of Saturn’s moons are visible in amateur scopes – we reveal how to get the best views of them on page 52.

For the best results you’ll need a minimum scope size of 6-8 inches and good seeing. Saturn is a gas giant planet, the second largest in the Solar System, and consists mainly of hydrogen and helium in a 3:1 ratio. Small amounts of other substances including water-ice and methane are also present. It’s believed the planet has a rocky core, perhaps up to 22x the mass of Earth and between 15,000-25,000km across. Surrounding this is a layer of liquid metallic hydrogen out to a radius of 30,000km, which is in turn covered by a liquid layer of helium-saturated molecular hydrogen. The final gaseous atmosphere is estimated to be around 1,000km deep. From Earth the visible cloud deck we see sits approximately 100km

RING SPOKES Probes have recorded radial spokes racing around the B Ring. A large scope and good seeing are essential.

SATURN OPPOSITION APRIL 35

below the outer edge of Saturn’s troposphere. Here the upper clouds consist of ammonia crystals, with clouds of ammonium hydrosulphide and water vapour below. Saturn radiates nearly three times the amount of energy it receives from the Sun. The most likely explanation for this is helium precipitation. Within Jupiter, liquid helium dissolves in liquid hydrogen. However, inside Saturn, cooler overall temperatures mean that helium remains in droplet form. As these droplets ‘rain’ towards the centre of the planet they get compressed and heat up. This mechanism also explains why there is an apparent deficiency of helium in Saturn’s outer layers. The planet’s core is estimated to be around 12,000-15,000 º C. The fluid metallic hydrogen layers within Saturn generate a magnetic field which, like the one surrounding Earth, creates a ‘bubble’ – a magnetosphere within the solar wind. And like on Earth, interactions between Saturn’s magnetosphere and the solar wind eventually give rise to aurorae around Saturn’s magnetic poles.

Observing at opposition The Ringed Planet has a short day, lasting just 10 and a half hours. The planet’s equatorial regions bulge due to this rapid rotation and the globe looks slightly squashed when seen through a telescope. Its atmosphere is bland compared to that of dynamic Jupiter. There are belts visible, but they are quite subtle, and the colours present tend to be pale

VIRGO

Spica

κ Saturn

yellows, greens, reds, purples and blues. Filters can help bring out features on the globe; we’d recommend you use an 8-inch or larger scope to ensure the view is bright enough to see them. A yellow filter will give a more defined view of the planet, helping to bring out some of the belts. Red, orange and green filters may also make certain belt structures clearer. A light green or magenta filter can reveal detail in the ring system, >

Þ Saturn will appear as a small dot to the naked eye on 28 April

þ The planet will cross into Virgo in the coming months

109 CU

ζ

μ

β

VIRGO

ι

Zubeneschamali

κ

Saturn (NOT TO SCALE)

31 Jul

1 Apr

λ

LIBRA γ

Spica

α

α Zubenelgenubi

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IMAGING SATURN

Þ An afocal setup – camera pointing down eyepiece – resulted in a fuzzy shot of Saturn Þ This hexagonal cloud system rings Saturn’s north pole; each straight edge is longer than our planet is wide > while bright clouds in the planet’s atmosphere benefit from a green or blue-green filter. Closer in, Saturn’s atmosphere is more interesting. Large storms pop up occasionally and these can be seen from Earth as bright spots. A particularly large storm that occurred in 2010 and 2011 was eventually seen to encircle the entire globe. In the early 1980s the Voyager mission detected an odd hexagonal feature surrounding the north pole of the planet. Subsequently imaged by the Cassini spacecraft 32 years later, it appears to be a hexagonal standing wave with jet stream winds travelling at 360km/h. The whole feature rotates in 10 hours, 39 minutes and 24 seconds, the same period as radio emissions from the planet, which in turn are linked to Saturn’s interior. Each straight edge of the hexagon measures approximately 14,000km, larger than the diameter of Earth.

ASA/JPL/SSI/JASON MAJOR, PETE LAWRENCE X 5, ILLUSTRATION BY PAUL WOTTON

Ring dynasty Undoubtedly, Saturn’s main attraction when viewed through a telescope is its impressive ring system. There are three main rings visible through amateur telescopes. The outermost A Ring is separated from the marginally brighter B Ring by a ‘narrow’ 4,700km-wide gap known as the Cassini Division, though spacecraft images of the gap show it to be populated with material and ringlets of its own. The formation of the Cassini Division is linked to resonant gravitational forces caused by Saturn’s 400km diameter moon Mimas, and it can be seen with a 4-inch scope if the conditions are steady. The third main ring visible from Earth is the C Ring, sometimes called the Crepe Ring. It sits inside the B Ring and can be quite tricky to detect. Numerous other rings have been recorded by spacecraft close to the main ring system. There’s also a bizarre diffuse feature known as the Phoebe Ring, first detected using the Spitzer Space Telescope in 2009. It lies at a distance of 12 million km from the planet, is tilted to the equatorial plane by 27º and orbits backwards. skyatnightmagazine.com 2013

Þ Using a monochrome high frame rate camera with filters gave a crisper image Saturn is a rewarding planet to image but it’s dim compared to Jupiter or Mars at opposition, so it can sometimes be a challenge. Afocal imaging, which is where you point a camera down the eyepiece of a telescope, can produce acceptable results – but you may find that delicate structures are lost if you use this technique. For best results, you need to keep the planet bright in the image. To do this you may need to turn the ISO up and extend the exposure time, something that makes keeping everything still just that little bit harder. Earth’s atmosphere isn’t the most stable thing to look through and wobbles caused by turbulence really interfere, so a single image will always be worse than one

taken with a high frame rate camera. The reason for this is that high frame rate cameras take lots of shots in rapid succession. The best ones are extracted and averaged together to produce a smoother end result, which can be sharpened to bring out detail. Picking the best images from a set of thousands of shots can be done relatively easily by using one of several programs designed for the task. These include AutoStakkert!, RegiStax and AviStack, which are all free. RGB-filtered images taken with a monochrome camera tend to be better than those taken with a one-shot colour camera. A limit of two to three minutes per channel should avoid excessive blurring due to Saturn’s fast rotation.

The rings are composed of separate bodies, ranging in size from 1cm up to 10m across, all in orbit around Saturn. It’s estimated that if you gathered all the ring material together you could form a body similar in size to the moon Mimas. The A Ring has a maximum diameter of 274,000km, but the rings are only thought to be between 10m and 1km thick. Close to the outer edge of the A Ring is the Encke Gap. At just 325km wide, this thin, dark streak is regarded as a bit of a test for high-resolution imagers. It can be seen visually when the rings are wide open and the conditions steady, so long as you

SATURN OPPOSITION APRIL 37

Rings seen edgeon from Earth

Top of rings seen from Earth Earth

Underside of rings seen from Earth

Rings seen edgeon from Earth

Our view of Saturn’s rings depends on where the planet is in its orbit

have a 10-inch or larger scope at a magnification of 450x or more. At opposition, the shadows cast by the ring ‘particles’ on one another are hidden from view and the rings can appear to brighten for a few days either side of opposition date. This is known as the Seeliger effect and you can find out more about it – including how to catch it on camera – on page 60. Saturn is tilted relative to the plane of the Solar System by nearly 27º and, like Earth, experiences seasons. The planet takes around 29.5 years to orbit the Sun, and over this period we get to see two Saturnian solstices, when each pole alternately points towards us, and two equinoxes, when Saturn appears side on. During an equinox, the rings become edge-on to us and all but fade from view unless you’re using a large telescope. The last so called ‘ring-plane crossing’ occurred in September 2009. The next one is due to take place in March 2025. The rings also cast and receive shadows. Before this year’s opposition, we’ll see the planet’s globe cast a shadow onto the western part of the rings as they pass behind the globe’s upper-right (northwest) edge. As opposition approaches, the shadow decreases in size until it becomes a sliver of darkness symmetrical on each side of the globe. After 28 April and opposition, the shadow on the rings will grow behind the upper-left (northeast) edge of the globe. The shadows cast by the rings aren’t always that easy to see – sometimes they become hidden beneath the rings. Before opposition, you may just be able to glimpse a dark ring shadow on Saturn’s globe to the north of where the rings pass in front

of the disc. After opposition, this should become easier to see to the south of the edge of the A Ring. At the moment, Saturn is heading towards its northern summer solstice, which occurs on 25 May 2017. This means that the rings will continue to tilt open to us right up to that date. At present they are tilted open by around 18º. Despite relatively low altitudes from the UK, Saturn still presents one of the most beautiful sights in the entire sky. Make sure you don’t miss the view. S

Þ Saturn’s rings will be tilted open by 18º when at opposition

ABOUT THE WRITER Pete Lawrence is an experienced imager, presenter of The Sky at Night and writer of our monthly sky guide – see page 52 for top tips on spotting the Ringed Planet’s moons.

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36

Light

revolution Will Gater investigates how new technology and a fresh approach to lighting our roads will affect the future of our night skies

NASA EARTH OBSERVATORY/NOAA NGDC

F

rom its orbit 824km above Earth’s surface, the Suomi National Polarorbiting Partnership (NPP) satellite has an incredible view of our planet. In images returned from the spacecraft since its launch in 2011, brilliant white wisps of cloud drift over dazzling azure oceans while major landmasses stand out in spectacular detail, many outlined by swirling, turquoise coastlines. Look closely at the pictures and intricate river systems, verdant forests and vast deserts become clear. It’s fair to say that the NASA/NOAA satellite is one of our most powerful eyes in orbit. But one particular Suomi NPP image – released late last year – shows something that doesn’t impress most astronomers one bit: light streaming into the night sky. Suomi NPP’s instruments had captured our planet at night, the lights of the world’s scattered towns and sprawling cities glowing against a deep-blue Earth swathed in darkness. Just as in daylight Suomi NPP revealed impressive detail on the surface of our planet, at night its imaging suite picked out the lights from individual roads and villages. The M25 motorway around London is clear to see encircling the capital. Farther afield, the northern end of the River Nile and the roads branching out from Moscow stand out with remarkable clarity. In fact the outline > ABOUT THE WRITER Will Gater is Sky at Night Magazine’s features editor and a keen amateur astrophotographer. He holds a degree in astrophysics from University College London.

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YOUR FIRST TELESCOPE JANUARY 37

Europe’s biggest cities shine brightest in this Suomi NPP shot, but the glow from towns and roads is unmistakable

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> of the whole of northern Europe is clearly defined by a speckled patchwork of myriad lights. “To many people, the lights visible from space, strewn across the Earth, at night are a symbol of the dynamism of the human race,” says Bob Mizon, from the British Astronomical Association’s Campaign for Dark Skies. “However, all the light that travels above the horizontal is in effect wasted, and when we consider that Europe alone spends about £1.5 billion lighting up the sky every year, we might revise our view.”

level of light pollution at their observing sites. “Because this sideways directed light is not easy to measure from above, the ground truth of sky brightness monitoring is a very valuable complement to the data from satellites,” Kardel says. In the UK, the Campaign for Dark Skies and the Campaign to Protect Rural England have been running an annual ‘star count’ since 2006. The survey happens around January and February time, when amateur astronomers across the country are asked to count how many stars they can see within the rectangle marked by the stars Betelgeuse, Bellatrix, Rigel and Saiph in Orion. “The Star Count isn’t an exact science. It is subjective and factors such as eyesight come in to it,” says Emma Marrington from the Campaign to Protect Rural England. “But it does give an indication of the light pollution that is masking the night sky in many locations. We say that if people can see fewer than 10 stars in the constellation, then that illustrates severe light pollution. In a truly dark sky you could see more than 30.” In the 2012 Star Count – which had 981 participants – 39 per cent of respondents counted between six and 10 stars, while 14 per cent recorded seeing five or less stars. With over half of the respondents recording what the Campaign to Protect Rural England

“It is clear from the 2012 Star Count that much of our night skies are far from pristine”

The dying of the night Many of the bright, densely populated regions in Suomi NPP’s image are indeed badly light polluted, says the International Dark Sky Association’s Scott Kardel. But, he adds, since the image shows upwardly directed light, we shouldn’t assume that necessarily translates to a glowing night sky. “Upwardly directed light certainly contributes to light pollution, but relatively recent work shows that it does so over a much smaller area than light that is directed just above the horizontal,” he says. “The sideways-directed light contributes to glare as well as sky glow and is not easily measured by satellite.” It’s for this reason that, in recent years, amateur astronomers have been called upon to survey the

þ Light pollution is a

problem across much of the northern hemisphere

SPECIAL REPORT APRIL 43

calls “severe light pollution”, it is clear that much of the UK’s night skies are far from pristine. So what does the future hold for our view of the heavens and how will amateur astronomers be affected in the decades to come? It’s possible there’s good news on the horizon.

Technological gains

Þ Surveys like the Orion Star Count can help monitor light pollution þ The LED streetlights being installed in Sheffield should scatter less light upwards

But how will the new LED technology affect light pollution levels more generally? “LEDs offer both promise and peril,” says Kardel. “On one hand it is now cheaper and easier to create light than ever before. That can lead to excessive use of light at night. On the other hand LEDs are very >

NASA EARTH OBSERVATORY/NOAA NGDC, WILL GATER, AMEY

In the UK there’s been something of a minor revolution in our streetlighting in recent years. The most visible manifestation of this transformation has undoubtedly been in the form of a new generation of LED (light-emitting diode) streetlights that are popping up all over the country. In Sheffield, the city council is upgrading 68,000 streetlights to the new LED technology in order to save energy and cut carbon emissions. “The LED lanterns were chosen as they are a very energy efficient and reliable light,” says Graham Scragg from Amey, the contractor that is installing the streetlights on behalf of the council. “The nature of the lights means that we are putting the right light at the right place at the right time. The lights themselves have very advanced optics so are very targeted to the footprint of the highways boundary. This means that light points downward and virtually none is emitted upwards, so glare over the city will be significantly reduced.” The effect of this change for astronomers living or observing in the Peak District could be dramatic. “After five years, when the lights are fully installed, Sheffield will no longer be visible from the Peak District,” says Scragg.

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44

GETTY, AMEY, ALAMY

particularly in the middle of the night. But they could also choose to install far brighter lights than those that existed before, or to light up new areas that were unlit before, and this would make the sky brighter. We need to monitor the changes.” LED lighting technology also presents another issue for astronomers: LED lighting fixtures generally emit much bluer light than the old-style streetlighting, which tends to be a more yellowy-red colour. That might not seem such a big issue until you consider what would happen if the LED lights weren’t shielded, or directed, effectively and light escaped into the night sky. “In general blue light is worse for astronomers because the sky is good at scattering blue light. That’s why it’s blue in the daytime,” says Kyba. “The total amount of light returned to Earth from a blue light will be larger than for a red light. The only caveat is that red light can travel farther through the atmosphere, so it depends on how close the observing site is to the city. For amateur astronomers who are likely to observe near cities blue light is much worse.” > directional, so it is easy to ensure that light is properly pointed downward.” Not only that, but the new LED streetlights give more control to those operating them. “This allows them to be used with more advanced controls that can allow them to be turned off or dimmed when not needed,” Kardel notes. Yet while where the new LED lights shine is much easier to control, if any light does escape into the night sky from them it’ll cause considerable problems for astrophotographers. Traditionally, amateur astronomers have been able to use specialist filters to reduce the effects of light pollution in their images. These filters work by allowing through the wavelengths of light associated with astronomical objects while blocking several specific wavelengths that are emitted from streetlamps. But while older streetlamps emit light at specific, narrow wavelengths, for example that of glowing sodium, the new white LED lights shine across a wider swathe of wavelengths. “The wide spectrum of white lights is bad news for filter users,” says Mizon. “However, the vast majority of people who enjoy the night sky have no filters, nor even cameras or telescopes, and where the light goes (or doesn’t go!) is more important to them than its colour.” To Dr Christopher Kyba of the Freie Universität Berlin, who studies light pollution, it’s not yet clear what overall effect the new LED streetlighting technology will have on our night skies. “There are too many things changing at the same time and we don’t know how communities will choose to light the streets,” he says. “If they make use of the dimming capabilities of LEDs then the sky could get darker,

skyatnightmagazine.com 2013

Þ The orange haze of current streetlights – this is the view over Birmingham

þ Although LED lights, left, cause less light pollution than their older counterparts, they could still affect astro imagers

Flicking the switch It’s not just new technologies that are changing the face of the UK’s streetlighting. Other subtle changes are occurring too: for example numerous county councils are now turning off streetlights in the small hours. And it’s not only astronomers, observing in their gardens, who benefit from a nearby streetlight turning off late at night. These schemes save considerable amounts of money too. Nottinghamshire County Council estimates it will save £1.25 million (at 2010/2011 electricity prices) each year by turning off or dimming sections of street lighting, either between certain times or, in some cases, permanently. The Highways Agency too has implemented a programme of switching off the lighting on certain stretches of England’s motorway network, a move that was driven mainly by a desire to cut carbon emissions. “On the one hand there are the environmental benefits, but on the other hand we had to consider the road safety side of things. We needed to make sure it was safe to do this,” says Stuart Thompson from the Highways Agency. “In 2007 the Highways Agency revised the standards for lighting and we looked at the safety case for where lighting was required. Prior to that all the policy on lighting had been developed in the 1970s.” Motorway lighting was deemed to provide a safety benefit of roughly 30 per cent in the 1970s, Thompson explains. “In 2007 we looked again at the safety benefit of lighting, factoring in advancements in vehicle [technology]. Partly because of those advancements and also the ways roads are constructed these days, we found that lighting has about a 10 per cent benefit on safety. So >

YOUR FIRST TELESCOPE JANUARY 37

LIGHT POLLUTION IN THE UK

KEY

Apparent magnitude of the faintest stars visible to the naked eye

Where to find the darkest skies the UK has to offer

+3.75 to +4.0

+5.0 to +5.25

+4.0 to +4.25

+5.25 to +5.5

+4.25 to +4.5

+5.5 to +5.75

+4.5 to +4.75

+5.75 to +6.0

+4.75 to +5.0

The apparent magnitude of a star is a measure of its brightness as seen from Earth. The brighter a star, the lower its magnitude. Areas where the faintest stars (mag. +5.75 to mag. +6.0) are visible have the darkest skies and are shown in grey. In these areas these stars are at the limit of visibility for the naked eye; to see anything fainter, you would need binoculars or a telescope. At the other end of the scale, areas where only the brightest stars (mag. +3.75 to mag. +4.0) can be seen, are shown in red.

Aberdeen

Glasgow

Edinburgh

Newcastle Middlesbrough

Belfast

Leeds Manchester Liverpool

Dublin

Nottingham Norwich Birmingham Cambridge Cork Swansea

Oxford Cardiff

London

Bristol Southampton

Exeter

Portsmouth

Eastbourne

Plymouth

LIMITING MAGNITUDE OVERLAY: P CINZANO (1), F FALCHI (1) AND CD ELVIDGE (2): ‘NAKED EYE STAR VISIBILITY AND LIMITING MAGNITUDE MAPPED FROM DMSP-OLS SATELLITE DATA’, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY (2001), VOLUME 323, PP 34-46, WILEY-BLACKWELL. (1) DIPARTIMENTO DI ASTRONOMIA, UNIVERSITÀ DI PADOVA, ITALY, (2) OFFICE OF THE DIRECTOR, NOAA NATIONAL GEOPHYSICAL DATA CENTER, BOULDER, CO; MAP CONVERSION BY PAUL WOOTTON

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46 SPECIAL REPORT APRIL

> there are other ways of achieving safety that give us a greater benefit.” The Highways Agency project began in 2009 by switching off the lights between midnight and 5am on parts of the M2, M4, M5 and M27. Careful consideration went into deciding where the switchoffs would happen and if the light was required. “We looked at traffic levels and did a whole load of safety analysis before we decided to switch off the lights,” Thompson explains. “We found six sites where the traffic volumes dropped significantly between midnight and 5am and where there weren’t a lot of accidents, which allowed us to switch off the lights between those hours.”

Þ The M5 is one place where lights are switched off during the small hours

But some are nevertheless concerned about the effect of these switch-offs on drivers. “Motorways research has shown that 2.6 per cent of accidents are fatal where street lighting is present, compared to 4.3 per cent of accidents where it is not,” says Paul Watters, head of roads policy at the AA. “The AA believes motorway lighting provides an additional safety margin particularly at times of bad weather and also improves driver ‘comfort’, with motorways being generally featureless, and with relatively high incidences of tiredness and sleep accidents. Drivers tend not to like frequent transmission between lit and unlit sections, which increases stress and fatigue. Ideally the AA would like to see energy efficient, full cut-off, dimmable lighting in preference to switch-offs. Clearly the Highways Agency will need to monitor the impact and respond quickly to any adverse effect on safety.” As with LED technology, it’s not immediately clear if the street and motorway lighting switchoffs are having a noticeable effect on overall light pollution levels. And it’s certainly not obvious what the future holds for our night skies. Who knows what the successors of Suomi NPP will see when they gaze down at Earth at night. Even if light pollution does increase, one thing’s for certain: it won’t stop astronomers looking up. S

“It’s not clear if lighting switchoffs are having a noticeable effect on light pollution”

ALAMY

Road to ruin? Since 2009 the project has expanded to several other sites and has resulted in permanent switchoffs in some areas. According to the Highways Agency, 95km of motorway has had its lighting permanently switched off since the project began, while lighting on almost 100km of motorway is now turned off between midnight and 5am. “This isn’t about just switching all the lights off across the whole motorway network. It’s about doing a careful analysis, applying the current [lighting] standard and, where that standard allows, switching off the lights,” says Thompson. skyatnightmagazine.com 2013

THE SKY GUIDE APRIL 47

The Sky Guide

April PETE LAWRENCE

An almost partial eclipse of the Moon Although it might not be that obvious, the rising full Moon on 25 April will undergo an almost partial eclipse. Only the tiniest amount of Earth’s dark umbral shadow will be crossing the lunar surface at this time.

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 brightening of Saturn’s rings during this opposition. STEPHEN TONKIN When he’s not doing astronomical outreach of one form or another, Stephen heads to the New Forest to explore 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

MONDAY Saturn’s largest moon, Titan, is at eastern elongation from the planet.

11

THURSDAY The weak Virginids meteor shower peaks near this date. It has a maximum zenithal rate of about five meteors an hour.

Look out for a beautiful waxing crescent Moon (1% lit) low in the west-northwest after sunset this evening.

14

SUNDAY Watch out for a delightful conjunction between the waxing crescent Moon (17% lit) and mag. –1.9 Jupiter this evening. The Moon will be closest to Jupiter around 21:30 BST (20:30 UT) – look for it about 2.5º below the planet.

16

TUESDAY  This is a great time to enjoy M3, an often overlooked globular cluster in Canes Venatici. At 01:00 BST (00:00 UT), M3 is at its highest in the sky, due south. Another overlooked globular, M5 in Serpens Caput, is also visible due south at around 02:30 BST (01:30 UT).

21

22

MONDAY The Lyrid meteor shower reaches its peak, but the 12-day-old Moon will cause a lot of interference. At peak, the Lyrids produce around 10 meteors per hour.

SUNDAY  Comet C/2011 L4 PANSTARRS will pass into the famous ‘W’ of Cassiopeia today. If it’s following predictions, it will be approaching 6th magnitude at this time. The comet doesn’t set as seen from the UK.

25

 THURSDAY

PETE LAWRENCE X 7

The full Moon undergoes a slight partial eclipse. Mid-eclipse is just after 21:00 BST (20:00 UT), when the extreme northern edge of the Moon is clipped by Earth’s shadow. See page 51. The Moon passes just under 4.5º to the south of mag. +0.3 Saturn.

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26

FRIDAY Tonight’s waning gibbous Moon (98% lit) offers a great opportunity to see the three giant craters Furnerius, Petavius and Langrenus close to the terminator.

27

SATURDAY The waning gibbous Moon (93% lit) sits 6º above mag. +1.0 star Antares (Alpha (a) Scorpii).

THE SKY GUIDE APRIL 49

What the team will be observing in April

2

TUESDAY Comet C/2011 L4 PANSTARRS no longer sets for much of the UK, although when due north it will scrape the horizon. The comet should still be a naked-eye object if it follows predictions. See page 51.

10

9

TUESDAY Saturn’s largest moon, Titan, is at western elongation today.

Comet C/2011 L4 PANSTARRS crosses the border of Andromeda and moves into Cassiopeia. The comet is currently circumpolar from the UK, meaning that it doesn’t set.

The Realm of Galaxies, a galaxy-rich part of the sky located in and above the Bowl of Virgo, is in a good position. A small telescope will show many distant galaxies as faint smudges, some of which form fabulous patterns such as Markarian’s Chain.

17

23

TUESDAY Comet C/2011 L4 PANSTARRS passes close to mag. +6.5 open cluster NGC 129 in Cassiopeia. The comet should be around the limit of naked-eye visibility if it follows predictions.

Will Gater “This month I’d really like to capture an image of Markarian’s Chain when the Moon is well out of the way. I’ve never tried imaging it so it should be a nice challenge.” Steve Richards “April is a great month for galaxy hunting in Leo and one of my favourite objects here is the Leo Trio, I am looking forward to imaging this triplet.”

WEDNESDAY 

WEDNESDAY Saturn’s largest moon, Titan, is at eastern elongation from the planet.

Pete Lawrence “Saturn will be at its best for the current period of observation and despite it being a bit low in the sky, I really can’t resist this beautiful planet. This is the object that gave me my first ‘wow’ moment in astronomy!”

Terms you need to know 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.

18

THURSDAY Mars is in conjunction with the Sun today. Although the planet can’t be seen at the moment, this does mark the point at which it will start to re-emerge into the morning sky. Just don’t expect it to do it quickly!

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

24

Allow 20 minutes to become dark-adapted WEDNESDAY

The full Moon passes less than 1º to the south of mag. +1.0 star Spica (Alpha (a) Virginis) this evening.

BINOCULARS 10x50 recommended PHOTO OPPORTUNITY Use a CCD, webcam or standard DSLR SMALL SCOPE Reflector/SCT under 150mm, refractor under 100mm

28

SUNDAY Saturn reaches opposition today, a time when it appears at its biggest and brightest for the year. There are other phenomena that occur at opposition, such as the Seeliger effect, which makes the rings brighten for a short period – see page 60.

30

TUESDAY Minor planet 4 Vesta is approaching open cluster M35 in Gemini. 4 Vesta is currently shining at mag. +8.4 and should be visible through binoculars. Look for M35 low in the west-northwest at around 23:00 BST (22:00 UT). See page 50.

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

1 May M35

4 Vesta passes M35

30 Apr

WHEN: All month; passes M35 from 29 April to 1 May, 2 2:00 BST (21:00 UT) to 23:00 BST (22:00 UT)

THE WINTER STARS are fast disappearing, but before they go there’s one final display we want to draw your attention to. Gemini, the Twins, plays host to a rather lovely open cluster known as M35. It lies near to the foot of one of the twins, not too far from mag. +3.3 star Propus (Eta (h) Geminorum). At mag. +5.0, M35 can be seen with the naked eye if the sky is dark and clear, but binoculars will give you a better view. Towards the end of the month, M35 can be found low in the western part of the sky. As the sky gets properly dark

1.5’

around 23:00 BST (22:00 UT) on 30 April, the cluster is about 15º above the horizon. If you can get a look at M35 at the end of April you should also be able to catch a glimpse of minor planet 4 Vesta passing by. At mag. +8.4 on 30 April, binoculars should reveal this 500km body fairly well. At the start of the month, 4 Vesta will be visible in slightly darker skies, nestled between the two horn stars of Taurus. Its passage throughout April then takes it straight towards M35. On the evening of the 29th, 4 Vesta will be

NGC 2158 29 Apr

Minor planet 4 Vesta will pass within half a Moon width of open cluster M35’s centre at the end of April, before heading on to Collinder 89

right next to the southwest border of the open cluster. On the 30th, it passes through M35’s southern extremity, separated from the centre of the cluster by 0.25º – half the apparent diameter of the full Moon. For reference, M35 itself has a diameter roughly equivalent to the

8 May 7 May 6 May 5 May

Collinder 89

4 May

μ

3 May

M35

2 May 1 May 30 Apr 29 Apr

η

28 Apr 27 Apr

E

1º

N

0.

PETE LAWRENCE X 4

5º

S

26 Apr

W

GEMINI

1

NGC 2129

The path of 4 Vesta from 26 April to 7 May; positions shown are for 22:00 BST (21:00 UT) on each evening

skyatnightmagazine.com 2013

!

NEED TO KNOW

An open cluster is a group of stars that formed together in the same cloud of gas and are gravitationally bound to each other.

apparent size of the full Moon in the sky. On 1 May, 4 Vesta exits the cluster from the southeast, continuing its passage into Gemini. There’s no scientific relevance to this event, but as long as you can locate M35 in the sky, it does give you a good opportunity to see the minor planet if you’ve never seen it before. Binoculars or a small telescope will not show any detail on 4 Vesta, as it’s too small and too distant for this. On 30 April, the minor planet will be a fraction over 3 AU from Earth – around 451 million km. What you’ll be looking for is a dim star-like object not too dissimilar to the cluster stars themselves. One way to make sure you’re looking at 4 Vesta is to sketch or image the cluster over the nights mentioned. If you see a ‘star’ moving through the southern extremities of M35, that will almost certainly be the minor planet.

THE SKY GUIDE APRIL 51 γ

The spring comet goes circumpolar

CEPHEUS

ECLIPSED

1 May

δ

can watch it all night long should you wish. At the start of the month, C/2011 L4 PANSTARRS should be close to the limit of naked eye visibility but fairly easy to pick up in a pair of binoculars. By the end of April, as it passes between the constellations of Cassiopeia and Cepheus, the comet will probably become a telescopic target. Estimations of the comet’s brightness come from a refinement of the magnitude formula for C/2011 L4 PANSTARRS deduced from real observations throughout January 2013. By the time you read this, the comet will have passed perihelion, its closest approach to the Sun. The shock of this encounter could mean that C/2011 L4 PANSTARRS is much brighter object than is currently predicted. We

An almost partial eclipse

ε Double Cluster

WHEN: All month. The Moon will interfere after 20 April

AT THE TIME of writing, Comet C/2011 L4 PANSTARRS is looking as if it’s going to underperform compared to estimates made at the end of 2012. Nonetheless, the comet should still be visible in the night sky and this month it has the benefit of becoming circumpolar. An object is circumpolar if it’s close enough to the north celestial pole that it can never dip below the horizon. In other words, C/2011 L4 PANSTARRS will be up all night. This should happen on 1 April, but it will be very low down when due north on this date. As we get further into April, the declination of C/2011 L4 PANSTARRS will increase, meaning the comet will get closer to Polaris. Consequently, its minimum altitude improves throughout the month, so you

CASSIOPEIA

PERSEUS

ι

κ

26 Apr

γ α

21 Apr

β

ζ

16 Apr

Comet C/2011 L4 PANSTARRS

γ

11 Apr

ν

λ

M31

κ

6 Apr

μ β

ι 1 Apr

σ

π

ο

ANDROMEDA

NW Star positions shown are correct for 22:00 BST (21:00 UT) on 1 April

certainly hope so, but at present there’s no guarantee that this will take place. Whatever happens to its brightness, it is certainly worth

heading out to try to find this fleeting visitor – once the comet has gone, it is not expected to return to the inner Solar System for at least 110,000 years.

NORMAL Viewedfrom: Localtime: Field of view: Magnitudes: 6.5 5.5 4.5 3.5 2.5 1.5 Star Central British 23:00:00 Isles 55∞ 00' 00.0" star 02∞ 30' 00.0" 2013/03/18 W Azimuth (∞):Multiple 341.2858∞ 54∞ 00' 00.0" JD 2456370.46 N Altitude (∞): Variable +15.9289∞ star

WHEN: 25 April from moonrise; 20:30 BST (19:30 UT) from the centre of the UK

THERE’S AN ALMOST partial eclipse of the Moon on 25 April, visible low in the southeast as the Moon is rising. If you’ve never heard of an ‘almost partial lunar eclipse’ before, it’s because we’ve coined the term ourselves. However, it is the only way to really describe what will happen. Earth’s shadow has two parts, which are arranged like a bullseye. The inner part, called the umbra, is the proper shadow that produces visible lunar eclipses. The outer part, called the penumbra, is much weaker and hard to see. The join where the shadows meet is not sharp and a gradual darkening takes place as you move from the penumbra to the umbra. Technically, the umbra does clip

Earth’s shadow will make the northern edge of the Moon appear darker than usual on the 25th

the northern edge of the Moon on the 25th, producing a true partial eclipse, but the clipping is so slight what you’ll most likely see will be a subtle shading across the Moon’s face. Greatest eclipse occurs at 21:07 BST (20:07 UT) when the Moon will have a rather disappointing altitude of 4º as seen from the centre of the UK. If you witness moonrise on the evening of 25 April, stick

with the Moon and see if you can detect this subtle eclipse shading. The weak penumbral shadow leaves the Moon’s face just after 23:00 BST (22:00 UT).

!

NEED TO KNOW

The penumbra is the lighter shadow cast by an eclipsing body during a partial eclipse; it is also the name given to the outer region of a sunspot group.

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52

THE PLANETS Pick of the month

Saturn Iapetus 1 Apr 5 Apr

SATURN

1 arcminute

BEST TIME IN APRIL:

10 Apr

28 April, 00:50 BST (27 April, 23:50 UT) ALTITUDE: 23º LOCATION: Libra DIRECTION: South

5 6 27 28 7 29 30 8

15 Apr

9

26

16 1,17 Titan 2,18 3,19

10

11

2

24

3

4 25

1

23

15

22

21

13,29

14,30

4,20

5,21

12

13

6,22 14

Hyperion 20

19 11,27 18 10,26 9,25 17 8,24 7,23 16 15

12,28

RECOMMENDED EQUIPMENT:

3-inch telescope or larger

20 Apr 25 Apr

FEATURES OF INTEREST:

Rings, bright moons, occassional storms may be visible as white spots on Saturn’s disc

N 30 Apr

SATURN IS AT opposition this month on 28 April – you can read more about the general appearance of the planet and its rings at this time on page 32. Though it’s a

Four of Saturn’s moons – Titan, Tethys, Dione and Rhea – can be easily seen in a 3-inch scope

Orbit region for inner moons Mimas, Enceladus, Tethys, Dione and Rhea

E

Orbital positions for Titan, Hyperion and Iapetus in April; positions correct for 01:00 BST (00:00 UT)

spectacular sight in itself, Saturn also has some amazing moons orbiting it and they are quite easy to spot using just a small telescope. The largest, Titan, can even be found using a pair of binoculars. There are six moons visually available to small telescopes and two more are within reach of larger instruments. The first is mag. +12.0 Enceladus, which is just visible with a 3-inch refractor and its upper magnification limit of around 150x. Then come Tethys, Dione and Rhea, all 10th-magnitude moons which shouldn’t present too much difficulty with a 3-inch telescope. Titan is noticeably brighter than the rest around 8th-magnitude and is best seen when it’s at greatest elongation

from the planet – this means when it’s at a point in its orbit that it appears to be at its farthest from Saturn as seen from our perspective on Earth. Next on the small telescope target list is Iapetus, a peculiar moon that changes brightness depending which side of Saturn it’s on. The moon always appears brighter when it’s to the west of Saturn than when it’s to the east; remember this as ‘west is best’. The difference is quite marked, as Iapetus varies from mag. +10.1 to mag. +11.9. A larger scope, say around 10 inches in diameter, is needed to see the moons Mimas and Hyperion – although Mimas orbits very close to the ring system and this can make it tricky to see.

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

MERCURY (NOT VISIBLE) 1 APRIL

PETE LAWRENCE X 2

MERCURY (NOT VISIBLE) 15 APRIL MERCURY (NOT VISIBLE) 30 APRIL

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SATURN 15 APRIL

VENUS 30 APRIL

URANUS (NOT VISIBLE) 15 APRIL

NEPTUNE (NOT VISIBLE) 15 APRIL

MARS (NOT VISIBLE) 15 APRIL JUPITER 15 APRIL

0”

10”

20” 30” 40” ARCSECONDS

50”

1’

THE SKY GUIDE APRIL 53

JUPITER BEST TIME IN APRIL:

and dismiss it as not showing very much. If this is the case, go back and stare directly at Jupiter for at least a couple of minutes. You’ll be amazed what you can actually see when you do this.

1 April, 20:30 BST (19:30 UT) ALTITUDE: 37º LOCATION: Taurus DIRECTION: West Jupiter is rapidly being VENUS engulfed by the evening twilight. Having put on a BEST TIME IN APRIL: fantastic display over the past 30 April, shortly after sunset few months, the planet is ALTITUDE: 3º (low) now moving into a position LOCATION: Aries which will put it out of view DIRECTION: West-northwest for a while. Venus passed behind the At the start of April, Sun at the end of last month, Jupiter becomes visible at and throughout April it around 20:30 BST (19:30 UT). slowly returns to the evening Its altitude at this time is sky. It is too close to the Sun just short of 40 º, a far cry for serious observation, but from the near 60 º you might be able to we enjoyed at the catch a glimpse start of the year. of this intense, A small scope mag. –3.8 will easily show planet shortly the planet’s after sunset, squashed disc and low on the its four brightest west-northwest satellites – the horizon. The time Þ Jupiter’s disc appears Galilean moons between sunset slightly squashed, the Io, Europa, result of its fast, 10-hour and Venus setting Ganymede and is longest at rotation speed Callisto. the end of the The gas giant’s disc looks month, but even on 30 April, slightly squashed through you’ve only got a window of the eyepiece because of 50 minutes. its fast rotation. Jupiter The appearance of Venus completes one full turn will improve next month in less than 10 hours, and but don’t expect the planet this causes the equatorial to become the beacon in the regions to bulge outwards. evening sky that it was in Using a small telescope the early part of 2012. Right and medium to high now, the timing of Venus magnification will reveal is rather poor. the principle belts on the Undeterred, we’ll show planet’s disc as well as larger you how to find Venus atmospheric disturbances, during the day in future such as the Great Red Spot Sky Guides, but for the and dark barges within the moment, the planet is really main belts. The Great Red too close to the Sun to do Spot sits in a hollow in the this safely. As far as this main belt known as the brilliant world is concerned, South Equatorial Belt. we’ll just have to be patient If you’re having trouble for a little longer. seeing detail on Jupiter, the best advice is to give NOT VISIBLE THIS MONTH the planet time. It’s easy MERCURY, MARS, to look at the planet’s disc URANUS and 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 APRIL 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 01 3

2

1

0

1

2

3

Arcminutes

Tethys

Dione

Rhea

Titan

Iapetus

Saturn

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54 011 L4 PAN

STARRS

α β

M

39

T

RT O N

Den

eb

δ

δ

S

Sum m er T rian

r os s

Albireo

How to use this chart

β

Alderamin

C

YG NU

C

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

u

α

α

γ N o rth er n

1 APR AT 01:00 BST > 15 APR AT 00:00 BST > 30 APR AT 23:00 BST

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THE SKY GUIDE APRIL 55

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56

DEEP-SKY TOUR With Steve Richards

Get ready to prowl the realm of Leo, the Lion, as we hunt its night-sky treasures ✓ 

Tick the box when you’ve seen each one

object in a 6-inch instrument its bright core will be clearly visible. Increasing the aperture to 10 inches will start to reveal some reasonable detail, but even Charles Messier described the galaxy as “a feeble nebula without star”!  SEEN IT

3

4

Spiral galaxy M96 is the most prominent member of the Leo 1 group

CHART: PETE LAWRENCE, PICTURE:ADAM BLOCK/SCIENCE PHOTO LIBRARY

1

2

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REGULUS

April is a good month to view the many galaxies within Leo, but before we visit any of these we’re going to call in on the brightest star in the constellation, mag. +1.4 Regulus (Alpha (α) Leonis). Regulus is a multiple star system made up of four stars, and among them is the wide colour-contrasting double of Regulus A and B, which have a separation of just over 177 arcseconds. The primary is a brilliant blue-white while the secondary is reddish in colour, and they make for a fine sight in a 4- to 6-inch telescope. Lying very close to the ecliptic, Regulus has regular close encounters with the Moon.  SEEN IT

M95

Our second object this month starts us off on our galaxy search, starting with M95. Part of the Leo 1 galaxy group, it can be found by sweeping 2.5º to the south from the centre of an imaginary line drawn between Regulus and mag. +3.4 Chort (Theta (θ) Leonis), the bright star that forms the Lion’s hip. M95 is a beautiful barred spiral galaxy with a magnitude of +9.7 and although it is a challenging

skyatnightmagazine.com 2013

6

M96

Our second galaxy – and second member of the Leo 1 group – is very close by. If you look just under 1º to the east of M95, you’ll reach spiral galaxy M96. It has a bright inner disc about 65,000 lightyears in diameter comprised of older yellow stars and a fainter outer halo extending to about 100,000 light years. A 10-inch telescope will reveal some faint dust lane detail, especially if you use averted vision. With a magnitude of +9.3 and a size of 7.8 arcminutes by 5.2 arcminutes, it is the most prominent galaxy in the Leo 1 group, which also includes nearby elliptical galaxy, M105.  SEEN IT

THE LEO TRIPLET

Our next object isn’t just one galaxy but three in a lovely grouping. Also known as the ‘Leo Trio’, this collection of galaxies – comprising M66, M65 and NGC 3628 – is very popular among astrophotographers. To find this group, start from Chort and sweep 2° south to mag. +5.3 star 73 Leonis, then move 1° east. A 6- to 8-inch telescope will show that oval M66 is the brightest of the three, with an almost stellar appearance towards the core, whereas M65 has a more cigar-shaped appearance and its core is less distinct. The third member of the group, edge-on NGC 3628, is somewhat more elusive.  SEEN IT

CALDWELL 40

Hop back to Chort for the first step to our penultimate object, the tight spiral galaxy Caldwell 40 (also designated NGC 3626). From Chort, head 5.2° due north to mag. +2.5 star Zosma (Delta (δ) Leonis) then head 2.7° southeast to find the galaxy. Having made a positioning error first time round, William Herschel ‘re-discovered’ this galaxy in March 1784. It shows a bright, condensed core that is almost stellar in appearance, with an elongated and rather faint outer halo orientated north-northwest to south-southeast when viewed through an 8- to 10-inch telescope at medium magnification.  SEEN IT

ABELL 1367

Our final object for this month is the Leo Cluster, one of the rich galaxy clusters recorded in the Abell catalogue. Imagine a line from mag. +2.0 star Algieba (Gamma (γ) Leonis) to Zosma and extended for half the distance again, and you’ll find mag. +4.5 star 93 Leonis. This star lies 0.9° to the northeast of the cluster’s centre. Deep-sky surveys have identified more than 500 galaxies within 1° of the centre of the Leo Cluster. Most are very faint, but more than 20 of them appear in the NGC catalogue – including NGC 3842, 3883, 3884, 3861, 3862, 3837 and 3864, all of which are visible in an 8-inch telescope. SEEN IT

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direction of mag. +1.9 star Alkaid (Eta (η) Ursae Majoris) and you should find the fuzzy patch of light that is spiral galaxy M94 – you may need to use averted vision. If you are unable to find it with a pair of 10x50s, try again in darker, more transparent conditions. Alternatively, switch to a pair of 15x70s, which will reveal M94 quite easily in dark suburban skies.  SEEN IT

BINOCULAR TOUR With Stephen Tonkin Our new Sky Guide section proves how much you can see without a telescope ✓ 

M53. Its apparent change in size and brightness is a good demonstration of the difference between direct and averted vision.  SEEN IT

10 x Melotte 111 is the third closest open cluster 50 to us and is made for binoculars. Look for mag. +4.4 star Gamma (γ) Comae Berenices – it’s midway between mag. +2.9 star Cor Caroli (Alpha (α) Canum Venaticorum) and mag. +2.1 star Denebola (Beta (β) Leonis). When you’ve found it, you should be able to see a misty patch of sky as well. A pair of 10x50s will reveal 30 or so stars. The cluster has been known since antiquity: to the ancient Greeks it was Queen Berenice of Egypt’s hair, dedicated to Aphrodite in return for her husband’s safe return from battle.  SEEN IT

3 M3

10 x From Diadem, imagine a line to mag. +3.0 50 star Seginus (Gamma (γ) Boötis). Imagine another between Cor Caroli and mag. +0.2 Arcturus (Alpha (α) Boötis). At the point these two lines intersect, in a star-sparse region of sky, is mag. +6.2 globular cluster M3. It is harder to find than M53 but, once you’ve located it, you’ll notice how much easier it is to see, being both larger and brighter. The cluster contains 150,000 stars – the brightest 45,000 of which were counted manually on a photographic plate at the Palomar Observatory in California.  SEEN IT

2 M53

10 x From Gamma Comae Berenices, look 15º 50 to the southeast to find mag. +4.3 star Diadem (Alpha (α) Comae Berenices). Just 1º to the northeast is a small misty patch, which will appear to grow in fuzziness and brightness if you centre it in the field of view then avert your gaze back to Diadem. This is mag. +7.6 globular cluster

6 LA SUPERBA

10 x Return to Chara and look 4.5° in the 50 direction of Mizar, and you’ll come across an orange star. This is Y Canum Venaticorum, named La Superba by 19th century Italian astronomer Angelo Secchi, not because of its colour, but on account of its beautiful spectrum, in which absorption lines from carbon compounds extinguish much of the light from blue-violet end. This carbon star is one of the coolest known, with a surface temperature of 2,200ºC.  SEEN IT

4 M94

10 x Imagine a line between Cor Caroli and 50 mag. +4.2 star Chara (Beta (β) Canum Venaticorum). From the mid-point, look 2º in the Phecda

URSA MAJOR

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15 x Head back to Cor Caroli and place it 70 just outside the right side of the field of view of a pair of 15x70s. Near the left edge of the view will be a little line of three 5thmagnitude stars. The top one is 19 Canum Venaticorum. From there, look 1° towards mag. +2.2 star Mizar (Zeta (ζ) Ursae Majoris) to find the Sunflower Galaxy, M63. It’s this month’s most challenging object, and once again you may need to use averted vision. This mag. +9.3 galaxy was one of the first to be identified as having a spiral structure, though this is not visible in binoculars.  SEEN IT

Tick the box when you’ve seen each one

1 BERENICE’S HAIR

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CHARTS AND PICTURES: PETE LAWRENCE

5º

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THE SKY GUIDE APRIL 59 N

MARE NECTARIS (600KM NORTHWEST)

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RHEITA VALLIS RHEITA

METIUS

YOUNG YOUNG D MALLET C MALLET D REIMARUS A

Vallis Rheita TYPE: Crater chain SIZE: 480km long, 38km wide AGE: Between 3.9 to 4.6 billion years old LOCATION: Latitude 42°S, longitude 51°E BEST TIME TO OBSERVE: Four days after new Moon (evening of 14 April) or three days after full Moon (after midnight on 27 April) RECOMMENDED EQUIPMENT: 2-inch telescope

The Vallis Rheita may be a result of the impact that created the Mare Nectaris, not visible above

MOONWATCH With Pete Lawrence “The northern part of the valley is created by a number of craterlets about 24km across. These overlap, creating a continuous path to the southeast” THE PHRASE ‘LUNAR valley’, probably conjures up an image of a steep walled groove cutting through the surface of the Moon. Indeed, there are many examples like this on the lunar surface, but the Vallis Rheita is something different altogether. This feature is made up of a string of craters, all apparently connected and all running in a more or less straight line across the lunar surface. The Vallis Rheita gets its name from the 71km-wide crater Rheita, which lies to the east of the northern end of the chain. Southwest of Rheita is another crater, Metius, slightly larger at 90km wide, and together they act as guardians over the northern end of the valley.

When you realise you’re looking at a crater chain, the shape of the Vallis Rheita becomes obvious. The northern part of the valley consists of a number of craterlets approximately 24km across. These overlap, creating a continuous path to the southeast. Eventually, they meet and feed into another crater, 71km-wide Young. Young’s southern edge touches 46km-wide Young D, which appears to mark Vallis Rheita’s southern end. However, if you can work through the jumble of craters, the valley does continue beyond Young D, leaving the southeast wall of 28km-wide crater Mallet C. Here the nature of the valley changes into a narrow channel measuring

about 6km across. It runs for about 40km before reaching 42km-wide crater Mallet D and for another 75km after it, before properly ending at 29km-wide crater Reimarus A. Where did the Vallis Rheita come from? The most probable explanation is that it formed as a result of the impact that created the Mare Nectaris. This 360km-diameter lunar sea lies about 600km to the northwest and the craters that form the Vallis Rheita align in a radial fashion – sort of. The Vallis Rheita bends in the middle as it passes Mallet C. If you draw a line along the narrow southern portion of the valley, it is certainly radial to the main area of the Mare Nectaris. However, the wider northern portion seems to align with the southern extremity of the sea: it’s on a tangent with the outer rim of the basin. It’s likely that a large piece of debris flung out as the Mare Nectaris formed resulted in the multiple impacts that created Vallis Rheita, but why there is a bend isn’t well understood. When the illumination is right, it’s fascinating to journey along the valley. The best time to do this is four days after new Moon or three days after full, which this month occurs on the evening of 14 April, or after midnight on 27 April. skyatnightmagazine.com 2013

60

ASTRO PHOTOGRAPHY With Pete Lawrence

The Seeliger effect Recommended equipment Planetary camera, telescope, tripod, remote shutter cable, layer-based graphics editor

RINGED PLANET SATURN is at opposition on 28 April, the time when it is in the opposite part of the sky to the Sun. For Saturn and the other superior planets – that’s Mars, Jupiter, Uranus and Neptune – this represents the time when they appear at their biggest and brightest as seen from Earth. Here we’re going to show you how to produce an image of Saturn that will demonstrate how much brighter its rings become at this time. Opposition doesn’t make a great deal of difference to the brightness of distant Uranus and Neptune, although they become visible all night long. Lying at a distance of about 1,430 million km from the Sun, Saturn is rather distant as well, so the difference in its brightness and size at opposition isn’t as dramatic as it is with Mars and Jupiter. However, Saturn’s appearance does still change markedly

at opposition thanks to a phenomenon called the Seeliger effect. To understand what’s going on here, imagine a bright floodlight pointing at a collection of poles stuck vertically into the ground in a circular bunch. Imagine you’re standing in front of the poles and that the light is directly behind them. From here all you’ll see will be the dark shadows cast by the poles towards you. As you walk around the poles toward the light, the angle measured from you to the poles and back to the light decreases. As you continue to walk, you’ll see more of the illuminated face of each pole. This makes the bunch of poles taken together appear brighter. However, look carefully and you’ll see that the poles inside the bunch will be partially covered by the shadows of the poles closer to the light. Eventually, you’ll get to a point where you

can stand with the light behind you. Your own shadow isn’t relevant here, so imagine crouching so that the main light reaches the poles unhindered by your body. From this position the shadows cast by the forward poles are hidden from view, lying directly behind the fully illuminated face of each pole. This is where the collection of poles collectively appears at its brightest – this is the Seeliger effect in action. If at this point you’re wondering what on Earth this has to do with Saturn, then I’d better explain. The rings of Saturn are a natural marvel consisting of many small particles made mainly of water-ice. These range in size from between 1cm and 10m across. When the Sun’s light falls on these particles, it illuminates their forward face and causes each particle to cast a shadow that may fall on the particles behind it. At opposition, those shadows are hidden from view just like those of the poles described above. As a consequence, the rings of Saturn appear brighter at the time of opposition.

Seeing the Seeliger Now if you’ve never seen or heard of this effect before you might be forgiven for thinking that the degree of brightening is actually quite small, but it’s not. It’s actually rather noticeable both visually and in astro images. This month, you can see this for yourself by imaging the planet through the whole of April, when the weather allows. The first signs of the Seeliger effect should occur in the days running

ALL PICTURES: PETE LAWRENCE

How to reveal the brightening of Saturn’s rings

STEP 1 We’ll assume that you’ve captured your images of Saturn using a planetary camera attached to a telescope. A colour or filtered monochrome camera is ideal. If you use a monochrome camera, you can proceed with monochrome or RGB colour images as you please. A monochrome view of Saturn through a blue filter tends to show the effect very well.

skyatnightmagazine.com 2013

STEP 2 Process your captured images with a registration stacking application such as RegiStax, AviStack or AutoStakkert! so that you end up with a final result that is smoother than the individual frames. Apply a small amount of wavelet sharpening as needed to produce an image to your liking. Note the settings you use on your first result and repeat for subsequent captures.

STEP 3 As with all images, it’s important to label the image so you can identify it later on. If you tweak the image in a layer-based editor such as Photoshop or GIMP, the label can be added visually within the image frame. It’s also worth adding the date and time into the file name in a yyyy-mm-dd_hh-mm-ss format. This will allow it to sort correctly with other images.

THE SKY GUIDE MARCH 61

The right half of your combined image will show how much brighter the rings become at opposition

up to opposition. If you can keep going into May, you should be able to see the rings dim down once again too. It’s a good idea to try to collect as many images as you can throughout this period as Saturn is quite low in the sky, so variations in atmospheric seeing will give you some results that are better than others. Imaging Saturn requires a telescope. The simplest way to capture the planet and its rings is to use a medium to high magnification eyepiece, centre the planet in the view and point a camera

STEP 4 The aim here is to compare the brightness changes within the rings of Saturn with the other parts of the planet. There will be little change in the overall brightness of the globe throughout April, so use that as a base reference. Use one image and adjust the others so that their globes look similar in appearance. Try to ignore the rings at this stage.

down the eyepiece. This is called afocal imaging and can produce acceptable results, but the planet may appear small and blurry. Keeping the camera still, focusing and getting the settings right isn’t always straightforward, so you may have to experiment a little bit. Use a high ISO, say 800-1600, and keep the exposure short. If your camera has a live viewing option, use that to make sure everything’s focused correctly. Hold the camera as square to the eyepiece as possible and try not to move it when you press the shutter button. A remote shutter release will help you to reduce unwanted vibrations. For a sharper result, attach a dedicated planetary camera to your telescope. This will allow you to obtain a larger image scale. The camera works by taking lots of still images in rapid succession, which must then be processed using a registration stacking application such as RegiStax, AutoStakkert! or AviStack. Our guide below shows you how, once you’ve collected these images, to present them in a way that will reveal the Seeliger effect.

Key technique GET THE SHOTS AND THE REST IS EASY

Digital images are easy to manipulate with the right graphics editor and we can exploit this to reveal the Seeliger effect on Saturn. The biggest challenge is to get a decent image of the planet both at the start of the month, when the effect isn’t taking place, and during opposition. If you can manage this, the difference in brightness caused by the Seeliger effect can be revealed using a simple presentation process. If everything works out properly, this will help you show just how dramatic this effect is for yourself.

 Send your image to: [email protected]

STEP 5 Select a good image from the start of the month and the best one you have taken close to opposition. Open your layer-based editor and load each image into a separate layer. Make the upper layer semi-transparent and use the scale and rotate tools to make it match the orientation and size of the lower image. Once done, make the upper image opaque again.

STEP 6 With the upper layer active, draw a selection box starting from the lower left corner of the image. Drag the box to the top, making sure its right edge cuts through Saturn’s middle. Delete the selection area so that you can see half of the normal planet and half with the rings glowing as a result of the Seeliger effect – our final image is shown as the main picture.

skyatnightmagazine.com 2013

62

Rise of the

Newtonian Allan Chapman looks back at the development of the first functional reflector and how it changed astronomy Learn more about Isaac Newton’s work in Brian Cox’s new series Science Britannica, which airs on BBC Two this Easter.

T

he introduction of the telescope to astronomy by Englishman Thomas Harriot in July 1609, and in November that year by Galileo, transformed what was a classical science beyond recognition. It revealed the lunar mountains, Jupiter’s moons, and countless stars in the Milky Way, none of which could have been imagined previously. But by 1614, the Jesuit priest-astronomer Niccolò Zucchi was experimenting with concave mirrors and concave eye glasses in search of better images than could be obtained with Galilean refractors, without success. By the 1660s, James Gregory in Scotland and Robert Hooke in London were also trying out mirrors. But it was Isaac Newton’s homemade telescope, presented to the Royal Society in January 1672, that constituted the real breakthrough.

GETTY, THINKSTOCK X 4, SCIENCE PHOTO LIBRARY, DR JEREMY BURGESS/SCIENCE PHOTO LIBRARY, ROYAL ASTRONOMICAL SOCIETY/SCIENCE PHOTO LIBRARY

Stunted progress Although early refractors revealed a breathtaking Universe invisible to the naked eye, the limitations imposed by contemporary glass technology were immediately felt. How could one see what was on the surfaces of the Sun, Moon, and planets, much less determine if they were inhabited, with singleelement lenses of no more than 2 or 3 inches in diameter in an instrument with an 18m focal length? Astronomical refractors had tiny fields of view, dim, aberrated images, and magnifications of 170x at most, even by 1665. Technically speaking, it was much

Þ Newton’s original sketch of his reflector design, with its revolutionary mirror angled at 45º easier to cast and figure a large-diameter speculum metal mirror than a lens, which is why from Zucchi onwards astronomers

hope to cast a mirror 30cm or more in diameter! By 1660 the telescope had turned astronomy into the first technology-driven science – their effectiveness imposed limits on what could be seen, which in turn led to a relentless drive to improve the technology in order to see yet more. Stimulated by the work of Gregory and Hooke, Newton had not only cast and figured a 1.5-inch tin and copper alloy mirror by 1669, but also devised a much

“By 1660 the telescope had turned astronomy into the first technology-driven science”

skyatnightmagazine.com 2013

experimented with mirrors. Whereas a lens needs two optical surfaces and a transparent interior, a metal mirror has only one optical surface. One might even

The Newtonian through time

A GREAT LEAP

FORWARD In spite of its small size, Newton’s first reflector, right, was a clear improvement on the longer refractors, even after the superior Keplerian (convex) eyepiece had superseded the original Galilean (concave) arrangement. This was because, when the speculum mirror was freshly polished, it gave a large field and a bright, sharp image. Newton announced to the Royal Society that its 35x magnification revealed abundant detail on the surface of the Moon. It was also good for the planets, showing Jupiter’s four largest moons with great distinctness, as well as the crescent Venus. And when Newton set up an open book some distance from the telescope, he found that he could read the print easily. Its small, compact design made it much simpler to handle than a long refractor. Alas, the poor

more efficient optical configuration to use it. Instead of tilting the image or, like Gregory, using a secondary concave curved mirror that required several optical surfaces to work perfectly together, Newton had a brilliant idea. Why not intercept the light reflected from the concave mirror just short of the focus with a secondary ‘flat’ mirror set at 45º? Light could then exit the tube via an eyepiece at the side. Newton’s primary mirror only had a 16.5cm focal length, yet when mounted on a ball joint, with a delicate screw-focusing mechanism, it performed amazingly well. The Newtonian reflector was born.

Light’s nature revealed Newton’s new invention possessed another enormous advantage: there was no chromatic aberration, as one found in lens telescopes. Without chromatic aberration, you get an image free of false colour, and by bringing all the rays of light to a single focus, it can potentially give a sharper result. The reason for this lack of aberration was simple, and tied in perfectly with Newton’s prior work on the spectrum. Since antiquity, philosophers had believed that white was the natural form of light, with colours arising from contamination with air or moisture. From experiments published in 1665, Hooke concluded that light was a waveform, which created a visual sensation of red at one peak and of blue at the other, with the intermediate colours forming as a mixture between the two, like an artist mixing his paints. In 1672, Newton

1672 Newton presents his reflector to the Royal Society. Its image quality is admired, but rapidly tarnishing mirrors inhibit its development. 1721 John Hadley demonstrates a Newtonian reflector with a 6-inch mirror of 6ft focal length to the Royal Society. Its 200x magnification makes it superior to the long refractors and its design is much more compact.

alloy of the speculum mirrors – combined with the airborne sulphur from coal smoke – caused Newton’s mirrors to rapidly tarnish and blacken. This problem was not overcome until the 18th century.

1781 William Herschel discovers Uranus using a homemade Newtonian that the Astronomer Royal declared superior to any commercially made one. 1846 William Lassell, brewer-astronomer of Liverpool, discovers Neptune’s satellite Triton with a homemade and equatorially mounted 24-inch Newtonian reflector. The mirrors he used had been ground by steam machinery. 1848 Engineer James Nasmyth builds a 20-inch ‘Nasmyth focus’ modified Newtonian. He uses it to study lunar features at high magnification. 1856-7 Using a new silvering process, Karl August von Steinheil of Munich, and Léon Foucault and Wilhelm Eichens of Paris build the first silvered-glass Newtonian. Lighter and brighter, glass would replace metal in reflectors and transform astronomy.

Þ Newton’s experiments with prisms showed that white light can be split into colours acknowledged that Hooke’s work had spurred him on to study the phenomenon of light and colour with two prisms. From his experiments, Newton concluded that all six colours produced by the prisms were primary properties of nature, not contaminations or mixtures, and that when a lens refracted light, it would inevitably separate out the colours, bringing each to its own unique focal point. And when you combined the colours, you got white light. It was one of the first great practical applications of pure physics research. S ABOUT THE WRITER Prof Allan Chapman is a science historian and astronomer. He is also a lecturer based at the University of Oxford’s Faculty of History.

1859 Revd Thomas W Webb popularises the Newtonian for amateurs, writing that those with specula of silvered glass are cheap and excellent. 1860–82 Many Victorian working men build glass-mirror Newtonians. These include Dorset’s ‘optical bricklayer’ Samuel Cooper, who obtained three photographs of the 1882 Venus transit with his 9-inch reflector. 1917 onwards Although the great

20th century reflecting telescopes on Mount Wilson, Palomar and elsewhere could be adapted as Newtonians, they are really giant prime-focus astronomical cameras and are not used visually.

Circa 1952 Patrick Moore uses his 12.5-inch reflector for his lunar cartographic work. It is an iconic ‘Grand Amateur’ Newtonian.

ASTRONOMY IN

ANTARCTICA

Spending a week on the frozen continent, Govert Schilling reports on the astronomy being carried out from the South Pole and the lives of the scientists who work there and his team perished on their way back, starved and frostbitten. My journey is almost luxurious in comparison, though there are no in-flight movies, hot meals or attendants. For almost eight hours, I sit shoulder to shoulder with technicians and scientists, all eager to do research at one of the most inhospitable places on the planet.

It’s the first half of December – Antarctic summer – and I’m on my way to the McMurdo Station on the coast of the Ross Ice Sea. Here I will spend almost a week investigating the fascinating science taking place at the bottom of the world, as part of the US National Science Foundation (NSF) Antarctic media visit programme. >

McMurdo Station is a fully functioning town as well as the largest research base in Antarctica; it even has an ATM

THINKSTOCK

S

itting in the Hercules LC-130 military transport aircraft ‘City of Christchurch’ on the way to Antarctica, I think about how recently my destination was a mysterious, frozen unknown. It’s only been a century since polar explorers Roald Amundsen and Robert Scott first reached the pole. Scott

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> Temperatures at McMurdo are unexpectedly high, around 0 º C; the huge NSF-provided orange bag with extreme cold weather gear seems like an exaggeration. McMurdo Station has the look and feel of a military camp or a miner’s village, offering its residents almost everything you can think of, including a post office, a barber shop, a coffee house and two bars, a heavy-duty shuttle service to the airfield, even a small church. And, of course, spectacular views of nearby Observatory Hill, the jagged Royal Society mountain range, and snow-capped and smoking Mount Erebus, the southernmost active volcano in the world.

Table talk In the galley, I share tables with professors, postdocs, pilots and plumbers alike. This is by far the best place to hear the latest gossip, or learn about exciting science programmes from a wide variety of researchers. For instance, a team led by Peter Clark from Oregon State University is about to study the melt rate of Antarctic glaciers at the end of the last Ice Age – important knowledge in our current era of climate change. It must be like this in the other 39 permanently manned research stations dotted around Antarctica, of which McMurdo is the largest. Just like the researchers who will spend long days in primitive field camps on the ice, I have

Þ A commemorative cross for Robert Scott sits atop Observatory Hill; Mount Erebus looms behind it

to attend medical instructions, safety briefings and survival classes. One evening, a safety staff member introduces me to NASA astronaut Stan Love, who has just arrived in Antarctica for a two-month stay, joining a group of volunteer meteorite hunters in the ANSMET programme (see box, page 68). “An ANSMET expedition is like a space mission,” Love tells me. “For weeks on end, you’re completely isolated from the rest of the world, in a hostile environment, totally dependent on a small group of colleagues. You’re vulnerable to all kinds of social and psychological stress. I believe the

þ Many Antarctic research stations are manned year round; some of these are marked on the map below

Orcados (ARG) Year-round research station

0

500

Maitri (IND)

Neumayer (GER)

Sou th O r k n ey Is l a n d s

Novolazarevskaya (RUS) Troll (NOR) Syowa (JAP) New Schwabenland

Sanae IV (ZAF)

1,000km

Q U E E N

Graham L a n d Palmer (US)

Vernadsky (UKR) San Martin (ARG) Palm

BRANSFIELD STRAIT

Rothera (UK)

Esperanza (ARG)

Arturo Prat (CHL)

O’Higgins (CHL)

L A N D

E nderby Land Mawson (AUS)

Belgrano II (ARG)

Mac. Rober t s o n Land

er L and

Marambio (ARG)

Am erica n Hig hlan d

0º

E l l swo r th Land

90ºW

AmundsenScott (US)

South Pole

90ºE

Mirny(RUS) Vostok (RUS)

180º

Demas Ice Tongue

Davis (AUS)

D

Comandante Ferraz (BRA)

M A U D

Halley (UK)

L

Casey (AUS)

King Sejong (KOR) Bellinghausen Artigas (URY) Great Wall (CHN) (RUS) Escudero (CHL) Frei (CHL) KING GEORGE ISLAND

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K L

McMurdo (US) Scott Base (NZ)

I

LARSEMANN HILLS

W

Jubany (GER)

E

S

Concordia (FRA/ITA)

A

N

M arie B yrd Land

Arctowski (POL)

Zhongshan (CHN) Progress 2 (RUS)

Dumont d’Urville (FRA)

SOUTH POLE ASTRONOMY APRIL 67

What makes Antarctica so special for astronomy?

EXTREME DRYNESS Þ All researchers are required to attend survival classes and medical training in the Antarctic

Þ Super-TIGER is prepped for launch; it smashed the flight record for a balloon mission, staying up for 55 days

Science on the snowy frontier WISSARD (Whillans Ice Stream Subglacial Access Research Drilling) is an interdisciplinary project to study water and ice dynamics, and the presence of microbial life in the Whillans subglacial lake. “If the test is successful, 13 tractors will move the whole installation to the actual drilling site, much closer to the pole,” says team member Ross Powell of the Northern Illinois University. On 27 January, samples from Lake Whillans were indeed collected, almost a month after a British mission to drill down to another subglacial Antarctic lake, Ellsworth, was called off for 2012. >

Þ Dryness is critical for the South Pole Telescope to accurately observe microwaves The air above the South Pole is extremely dry. The reason: cold air can’t hold a lot of water vapour and the polar vortex – a counterclockwise, jet-like flow of air circling the pole – prevents moist air from lower latitudes entering the polar region. As a result, Antarctica is the driest continent on the planet. In fact, it’s one huge desert. That’s good news for astronomers who study cosmic microwaves. Electromagnetic radiation in this millimetre regime – in between infrared and radio – is readily absorbed by water vapour (that’s why a glass of water heats up so quickly in a microwave oven: water molecules absorb microwaves very efficiently). So to observe microwaves from outer space, you need to be high and dry. Two of the best places for these kinds of observations are the Chajnantor plateau in the Chilean Atacama desert and the South Pole. At 5,000m, Chajnantor is higher than the South Pole (2,830m), but on average, Antarctic air is drier than Chilean air. Little wonder that both host big millimetre-wave telescopes.

The construction of the 10m South Pole Telescope, a project led by John Carlstrom of the University of Chicago, was completed in early 2007. Its main goal is a detailed study of the cosmic microwave background radiation – the faint ‘afterglow’ of the Big Bang. It’s the biggest telescope on the continent. Over the past five years, the South Pole Telescope has been used to detect distant clusters of galaxies, by looking for their ‘fingerprint’ in the background radiation. Over 500 new, distant clusters have been found, providing cosmologists with useful data on the origin and evolution of the large-scale structure of the Universe. The South Pole Telescope is now equipped with sensitive new detectors that can also measure the polarisation of the cosmic microwave background. Part of this polarisation signal could be due to primordial gravitational waves, generated as a result of the inflationary epoch in the very first tiny fraction of a second after the Big Bang. The driest – and coldest – place on Earth may well hold the key to understand the hottest phase of the Universe’s history.

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GOVERT SCHILLING, THINKSTOCK, DAVID VAUGHAN/SCIENCE PHOTO LIBRARY, NASA, ALAMY

meteorite hunters can learn valuable lessons from an astronaut.” Early next morning, a small white speck can be seen floating against the deep-blue sky. It’s Super-TIGER (Trans-Iron Galactic Element Recorder), a balloon-borne cosmic ray telescope that has just been launched from NASA’s Long Duration Balloon facility, a few miles away from McMurdo. Too bad I wasn’t there for the launch, especially since Super-TIGER would turn out to be a record-breaking mission, logging over 55 days of flight. Then again, I might have missed the opportunity of visiting the WISSARD test site, where scientists explain their technique to drill through the ice into one of Antarctica’s many subglacial lakes.

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Þ The author at AmundsenScott South Pole Station, the research site at the bottom of the world

< Scientists hope to find microbial life in sediments recovered from Antarctica’s subglacial lakes

> “One day, I hope to carry out similar research on the Jovian moon Europa,” adds planetary scientist Britney Schmidt of the University of Texas at Austin, “to look for micro-organisms in its subglacial ocean.” Monday 10 December is a day not to be forgotten. A three-hour Hercules flight takes me to the geographical South Pole – a place that has been visited by less than 10,000 people. The huge Amundsen-Scott South Pole Station looks insignificant in the vast expanse of

What makes Antarctica so special for astronomy?

EXTREME ISOLATION Isolated areas with little or no vegetation Antarctic ice sheet. But there’s more: the and with few confusing landmarks constitute glacial motion of the ice can bring old, a more promising hunting ground. buried meteorites to the surface, especially Prime examples, where lots of where the ice is pushed upward by the meteorites have indeed been Transantarctic Mountains. found, are the Sahara, the Every southern summer Nullarbor Plain in Australia season, ANSMET volunteers and Antarctica. survey particular regions, ANSMET (the acronym visually scanning their stands for Antarctica surroundings from Meteorites), a longsnowmobiles. Each running programme meteorite is photographed, sealed and labelled for Þ Antartica can hold onto meteorites for many currently led by Ralph Harvey of Case Western further analysis in a centuries – ALH84001 is 13,000 years old Reserve University in laboratory in Texas. Ohio, has found over 20,000 Antarctica’s extreme Have you ever tried finding a meteorite meteorites since 1976, the most isolation makes it a Valhalla in a forest? Even if you knew for sure it famous being ALH84001, which was there, it would be very hard to Þ ALH84001’s unusual for meteorite hunters. The came from Mars and was once downside: the meteorite recognise amid all the shrubs, roots and structures were once thought to contain fossil traces hunters themselves have to leaves. In a mountainous area, it’s even thought to be fossils of Martian microbes. cope with extreme isolation, harder: you probably wouldn’t notice a Obviously, dark meteorites are easily too. In an emergency, a rescue operation rock from space between all the terrestrial spotted against the white background of the might take days. boulders, rocks and pebbles.

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SOUTH POLE ASTRONOMY APRIL 69

What makes Antarctica so special for astronomy?

EXTREME COLD Þ The outside of the IceCube Neutrino Laboratory belies its size – detectors extend beneath to a depth of 2.5km blindingly white ice. It’s a sunny day with little wind, and a chill factor of just –38º C, which is not too bad. Still, even a small stroll is quite exhausting, since the pole is at an altitude of 2,830m. But it’s a fascinating experience. As science support manager Paul Sullivan says: “Antarctica gets into our blood. That’s why we come back all the time.” A short drive in a tracked snow vehicle takes me to the ‘Dark Sector’, where astronomers have set up instruments to study the cosmic microwave background and neutrinos from outer space. “This is really the best place to do this kind of research,” says South Pole Telescope senior scientist Brad Benson of the University of Chicago (see box, page 67). In the building next door, Ralph Auer of the University of Wisconsin Madison gives me a tour of the data centre of the IceCube Neutrino Observatory (see box, right). “IceCube may last for 50 years,” says Auer, “and we have plenty of ideas for expanding the experiment.” Kell Bliss of the National Oceanographic and Atmospheric Administration conducts meteorological experiments at the Atmospheric Research Observatory, and provides me with a small, sealed bottle of the ‘cleanest air on Earth’, freshly sampled at the pole. Later that day, my fingers almost freeze when I spend too much time taking pictures at the flag-surrounded ceremonial pole. I could have stayed here for days, but much too soon I have to board yet another Hercules to head back to McMurdo. >

Þ Flags ring the ceremonial south pole; the real one is simply marked with a sign and – naturally – a pole.

Without its low temperatures (Antarctica has been in deep-freeze for the past tens of millions of years) particle physicists would have little interest in this inhospitable continent. But the giant ice sheet, a few kilometres thick in most places, changes everything. Buried within the ice is the IceCube Neutrino Observatory, the “largest human construction that no one can see” according to principal investigator Francis Halzen of the University of Wisconsin Madison. It measures a whopping cubic kilometre. IceCube was completed two years ago. It is made up of more than 5,000 light-sensitive detectors, melted into the ice on 86 vertical strings up to a depth of around 2.5km. At that depth, the ice turns out to be incredibly clear, not to mention incredibly dark. Neutrinos from outer space – elusive elementary particles with no charge and almost no mass – pass through the ice in huge numbers. Very occasionally, a neutrino interacts with an atomic nucleus. This results in the production of a short-lived muon, which generates a minute flash of light that is registered by IceCube’s photomultiplier detectors.

By using a large number of detectors in a huge volume of ice, it is possible to reconstruct the muon’s flight path, which also gives you the direction from which the original neutrino came. Scientists hoped that the most energetic neutrinos could be traced back to cosmic sources like active galactic nuclei or gamma-ray bursts. So far, these expectations haven’t been fulfilled, says electrical engineer Perry Sandstrom. IceCube has detected large numbers of high-energy neutrinos, but they don’t seem to be originating from discrete sources in the Universe. “Then again,” says Sandstrom, “this is a discovery machine. You never know what you can expect.” Like the Amundsen-Scott South Pole Station itself, the IceCube Neutrino Laboratory, where all the data is collected and analysed, is built on struts, so it can be cranked up in the future when snow drifts start to become a problem. In the end, the ice wins, of course. “We’ll never be able to get the IceCube detectors out of the ice again,” says Sandstrom. “When the icecap melts in the distant future, they will end up in the ocean.”

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DR. MARK SKIDMORE/MSU/CORE FUNDING FOR THE WISSARD PROJECT COMES FROM THE US NATIONAL SCIENCE FOUNDATION - OFFICE OF POLAR PROGRAMS, NASA/ JSC/STANFORD UNIVERSITY X 2, GOVERT SCHILLING X 3, STEVE YUNCK/LOOK AT SCIENCES/SCIENCE PHOTO LIBRARY, THINKSTOCK X 2

IceCube’s detectors are set vertically in the ice, hoping to catch a rare neutrino interaction

70 SOUTH POLE ASTRONOMY APRIL

What makes Antarctica so special for astronomy?

EXTREME LOCATION Balloon missions like BLAST can be recovered and reused several times

Þ Adélie penguins are a common sight near McMurdo;

there are an estimated five million in the Ross Sea region

> The next day, at nearby Cape Royds, I join

biologist David Ainley of ecological consultants HT Harvey & Associates and his colleague Jean Pennycook, who study Adélie penguins. It’s Ainley’s 17th season in Antarctica, he tells me. “For my PhD work, I chose penguins because that would take me to this fascinating place,” he says. Over the years, he has collected huge amounts of data on feeding behaviour and population dynamics of these little birds, and on how they respond to environmental changes, like when a huge part of the Ross Ice Shelf broke loose in March 2000.

NASA/WALLOPS FLIGHT FACILITY, THINKSTOCK X 2

Scott’s spirit lives on

Almost all of Antarctica lies south of the Antarctic Circle. Close to the pole, the Sun won’t set for four or five months or so during the southern summer – at the actual South Pole, of course, there’s only one sunrise and one sunset per year. Astrophysicists make clever use of the prolonged daylight. Just outside McMurdo Station is NASA’s Long Duration Balloon Facility, where scientific payloads are prepared for launch underneath giant helium balloons. The polyethylene balloons inflate to a diameter of up to 140m when they rise to their nominal altitude of some 38km, high in Earth’s stratosphere. Temperature variations caused by the rising and setting Sun would cause such balloons to drop down during the night. But in Antarctica, where the summer Sun never sets, they stay aloft almost indefinitely, enabling extended observing runs. The balloon flights also profit from the prevailing anticyclone (east-to-west) wind pattern in Antarctica. Launched from close to McMurdo, they slowly drift around the pole, completing one circuit in a couple of weeks. The Super-TIGER cosmic ray telescope, launched on 9 December

skyatnightmagazine.com 2013

2012, recently broke the record with a flight duration of over 55 days. The BLAST submillimetre mission, launched on 25 December, was terminated after 16 days; EBEX (E/B Experiment, a programme to study the polarisation of the cosmic microwave background) took off on 29 December and lasted for 25.5 days. All these missions would have been impossible from a more northerly location. Almost all scientific balloon missions are terminated intentionally. The data collected needs to be recovered – most of it is usually stored onboard – and the more expensive parts of the payload, including telescope mirrors, cameras and detectors, can be used again. For instance, BLAST made its fifth flight this season. To enable a recovery operation, the payload is brought down when it is close to McMurdo again. So what happens at the Long Duration Balloon Facility during the prolonged Antarctic winters? Not much. In fact, all buildings – including the two giant payload assembly halls – are mounted on giant skis and are pulled away and stored at McMurdo to overwinter.

I can’t help feeling respect and admiration for all the scientists I meet here in Antarctica. They leave home for weeks or months on end to suffer extreme conditions in a harsh, perilous environment, risking injury or even death, just to add another brick to the edifice of science. Will they be honoured and remembered a century from now, like we honour and remember Roald Amundsen, Robert Scott, Ernest Shackleton and Richard Byrd? I really hope so. Antarctica hasn’t changed a lot since 1910, nor has the perseverance of its explorers. On the last day of my visit, I finally have the opportunity of visiting the Long Duration Balloon Facility. Mark Devlin of the University of Pennsylvania and his students are preparing yet another balloon-borne telescope, called BLAST (Balloon-borne Large-Aperture Submillimeter Telescope), poised to study magnetic fields in star-forming regions in the Milky Way (see box, left). “These experiments are very cheap compared to satellites,” he tells me. In the future, Devlin hopes to fly an Antarctic balloon-borne telescope to hunt for extrasolar planets. Back in New Zealand, I know one thing for sure. I have to come back here. Paul Sullivan was right. Antarctica gets in your blood. S ABOUT THE WRITER Govert Schilling is a journalist and the author of several astronomy books, including The Hunt for Planet X, The Atlas of Astronomical Discoveries and Evolving Comsos.

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ASTROPHOTOGRAPHY IN ANTARCTICA APRIL 73

EYES ON THE

ANTARCTIC

SKIES

The bottom of the world offers fertile hunting grounds for adventurous astro imagers

A

ntarctica has a special place in the minds of many daydreaming adventurers – a remote continent, encased in snow and ice, far from civilisation; one of the last great wildernesses on our planet. Only a hardy few have visited this frozen desert – perhaps that’s why the region’s night skies are some of the most spectacular, and untouched. In the darkness of polar winter the Southern Lights, the aurora australis, dance overhead, while the stars twinkle and the Milky Way arches across the sky. This starry scene is enjoyed by many of the people who work on the continent, especially those with cameras. Here we present a gallery of some of the best pictures captured by those living in the region – our eyes on the Antarctic skies.

Star trails over Harker Glacier, South Georgia Samantha Crimmin “This image was taken at about –10ºC on a beautiful, perfectly clear and still night. I left the camera going for one hour and 45 minutes then headed back out to retrieve it. In that time my boots froze solid.”

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 Aurora over Black Island Anthony Powell “Here we see people viewing the aurora from Black Island, where the remote satellite facility for US base McMurdo Station is. The Sun is below the horizon for four months at this latitude, and it is quite common to be able to walk outside at any time of the day and be greeted by aurorae in the sky.”

 The Milky Way over Black Island Anthony Powell “This picture, a frame from a timelapse sequence of the Galaxy moving across the sky, was taken in ambient temperatures of about –40ºC. Because there is no atmospheric pollution this is very close to what you see with the naked eye if you can stand to be outside long enough to let your eyes adjust. The camera was run off a car battery to keep it going in the cold.”

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ASTROPHOTOGRAPHY IN ANTARCTICA APRIL 75

 Stars over the Halley VI Research Station Sam Burrell “Once the Sun has gone down and winter starts, the Milky Way stretches across the sky, from the ground all the way above and behind your head. Here at Halley, the newest UK base, the air is crisp and clean, but our position on the continent results in rather poor seeing. As such the stars are brilliant, numerous and clear – yet shimmer and sparkle a great deal.”

THE EXPERT We get some top astrophotography advice from photographer Samantha Crimmin with good weather. In these instances the Moon dictated whether we captured star trails or the Milky Way – with bright moonlight and the reflection from the snow there was always too much light to get any detail from our Galaxy. One of my favourite images came about because of this though, the shot of star trails over the Harker Glacier.

What equipment do you use? I use a Canon EOS 5D MkII DSLR with a 17-40mm f/4 lens and a sturdy tripod. I also use a remote timer to take star trail images. I’m on my second as the first froze and snapped at –15°C. How do you choose your subjects? My best images were taken at the height of the Antarctic winter when travel is a real challenge. The island is deep in snow, so you need skis or snowshoes to get anywhere. I had a few winter camping trips that coincided

What are the skies like to the naked eye from where you photograph? Incredible. More stars than you can imagine. In winter there was so little light on the horizon that on one side the stars would meet the mountains and on the other would come down to the sea. For the best part of the coldest and darkest six months I would regularly find myself outside just staring upwards. What are the main challenges of astrophotography in the Antarctic? Getting there and being ashore in winter! The majority of visitors to the Antarctic come in the summer on cruise ships. For the most

part of their trip it is light for nearly 24 hours and even in the locations that do get dark a ship does not offer a stable platform for the long exposures needed for astrophotography. Another hurdle is the ever-changing weather. In the best part of a year I can recall about 10 really good clear nights and even then the clouds only ever held off for a couple of hours at a time. Batteries don’t last as long at –10ºC either. A tripod needs to stand up to very strong winds, lenses have to be protected against condensation and that’s not even considering the clothing. What advice do you have for anyone thinking of taking these kind of images? The weather, the location and the time of year play a big part in getting good images. I learnt what tends to work best by experience. I also found that planning my shots helped. After a while I knew where the Milky Way or Moon would be and at what time. But most of all, persevere. I spent a lot of time getting it wrong. I still do.

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 Star trails behind Hope Point Samantha Crimmin “Hope Point, South Georgia, is a foothill at the entrance of Cumberland Bay. In 1914, Ernest Shackleton launched the ship Endurance from Grytviken Harbour. In 1922 he returned to his ‘gateway to the Antarctic’ with another ship, Quest, and it was here he suffered a heart attack and died. His shipmates erected a cross in his memory. This image was taken on a particularly windy night, so the tripod was weighed down with snow. It looks out over Cumberland Bay towards the Allardyce mountain range.”

 Aurora over Scott Base Anthony Powell “This was one of the brightest auroral displays I have seen. It was bright enough to cast shadows on the ground, and was moving so fast it was difficult to line up the shots. The display lasted about 30 minutes and was gone.”

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ASTROPHOTOGRAPHY IN ANTARCTICA APRIL 77

 The Milky Way over King Edward Point Samantha Crimmin “Opposite King Edward Point Research Station is an abandoned whaling station, Grytviken. This image was taken from its shores in midwinter. The ground and the remains of the old jetty are covered in snow. The only artificial lights come from the research station.” S

If you’ve been inspired by these images, 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’ and ‘Our Solar System’. Find out more at www.rmg.co.uk/astrophoto

ABOUT THE PHOTOGRAPHERS SAMANTHA CRIMMIN Samantha Crimmin began working in the polar regions as a medical officer for the British Antarctic Survey. Since then she has worked for several other expeditions.

SAM BURRELL Sam Burrell is a meteorologist with the British Antarctic Survey. He spent 18 months overwintering at Halley VI Research Station on the Brunt Ice Shelf.

ANTHONY POWELL Communications technician Anthony Powell spent three years at New Zealand’s Scott Base, then another six winters and a number of summer seasons with the US Antarctic Program.

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Skills

Brush up your practical astronomy prowess with our team of experts

Contents The guide

How to

Sketching

Scope doctor Lost in space

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80

83

85

Choosing the right accessories to suit your needs

SKILLS

Set up a dual imaging system, part 2

Learn how to draw lunar crater Albategnius

Steve Richards answers your astro equipment queries

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Keith accepts an epic quest to reclaim his telescope

The guide

Choosing the right accessories With Paul Money

How to make smart choices when it comes to astronomy add-ons Eyepieces and filters are good early investments; they can make a huge difference to your observing experience

Here’s the thing: there are hundreds of accessories available. Once you’re comfortable with your basic setup – and we’ll assume you’re happy with your mount and tripod – what do you add next? Do you need to invest in anything at all? A good place to start is with the most essential accessories of them all – your eyepieces. Most telescopes are supplied with one or two, but that is no guarantee of their suitability or their quality. Your eyepieces are as important as your telescope’s main mirror or lens, as they take the light gathered by the scope and magnify it for your eye. Poor eyepiece optics could introduce aberrations that deteriorate the view; if you wear glasses, you may want to buy an eyepiece with particularly long eye relief to make observing more comfortable.

PAUL WHITFIELD X 5, STEVE RICHARDS

Beyond the essential

W

e’ve all heard it before: “The telescope is the important bit, right?” To some people, it is the thing that makes you an astronomer and is, as far as they are concerned, the be all and end all when it comes to stargazing. They are, of course, quite wrong. skyatnightmagazine.com 2013

A telescope tube is nothing without a suitable mount, tripod and eyepiece at the very least, and this is just the tip of the burgeoning world of astronomical accessories. Sometimes dismissed as ‘just extras’, they are often the important finishing touches that make stargazing enjoyable and fulfilling.

You should pay the same heed to the other accessories often bundled with new telescopes: finderscopes, Barlow lenses and (with refractors and compound scopes) star diagonals. But beyond these essential items, what you add to your astronomy toolkit entirely depends on what you want to achieve. Filters can help you see more detail in night-sky objects, but you’ll need different ones depending on whether you want to

SKILLS APRIL 79 Just a few of the useful extras for the budding astronomer. Clockwise from top: a dew heater, red light torch, filter wheel and smartphone app

AN OBSERVER’S ADVICE Paul Abel is a presenter on The Sky at Night As a visual planetary observer, the most invaluable tools I have are my filters. Essentially, an optical filter is a piece of material which, when attached to the eyepiece, allows some wavelengths of light through while stopping others. The effects can be remarkable: increasing the contrast of the belts of the gas giant planets, and emphasising Mars’s storms and white clouds. They even reveal that the vague cloud markings of Venus vary in appearance at different depths. If there was one thing I wish I’d had from the start, it would be these!

pick out the polar caps on Mars or the faintest regions of emission nebulae. If you live in an urban area that has a lot of street lighting you may find that a light pollution filter becomes a greater priority than either, regardless of what you want to see. If you regularly take your scope to a dark-sky observing site, on the other hand, a strong carry case to get it there and back in one piece may prove more useful. Likewise, portable power packs for computerised mounts might be optional if you can

Dew shields come into their own on cold nights, while power packs offer extra portability

simply run an extension cable from your kitchen, but they become invaluable when you are away from home.

Embarrassment of riches If your interest extends to imaging then there is an even wider range of accessories to consider. In addition to a camera and an adaptor to connect it to your scope, there are filter wheels to help you switch filters speedily, autoguiders to help you keep your target centred during long imaging sessions and dew heaters to keep the view fog free. These are just a few examples. Remember that ‘accessories’ don’t have to attach to the telescope itself. Star charts, guide books and even smartphone apps are invaluable if you want to start star hopping around the night sky with aplomb – and you’ll be hard pressed to protect your night vision while reading them without a red light torch. Apps have an added benefit if you want to travel abroad, in that they weigh nothing and, in some cases, can be set to match the sky over your location. Astronomers love to accessorise and it could be said that for every star in our Galaxy there is an appropriate astronomical add on. However, what this should serve to illustrate is that accessories are a vital part of your toolkit, and picking the ones that are right for you, your setup and your stargazing goals is worth some careful thought if you want the best experience. S

AN IMAGER’S ADVICE Will Gater is Sky at Night Magazine’s features editor My favourite imaging accessory has to be my Bahtinov mask. It makes nailing perfect focus ridiculously easy. Investing in a guide scope mount has been a huge help too, as it makes lining up my guide scope on a guide star – so I can iron out the tracking imperfections of my mount – a doddle; before I bought it I spent many frustrating, back-breaking hours twiddling the screws on a set of guide scope rings. Now it’s simply a case of adjusting a knob and a wheel until the star is centred.

skyatnightmagazine.com 2013

80

SKILLS

PART

How to

2

set up a dual imaging system With Steve Richards

System balanced, we show you how to take enhanced images

TOOLS AND MATERIALS BAHTINOV MASKS

These simple filters (below) fit over the main lens of your telescope to help you achieve accurate and fast focus when imaging CAPTURE SOFTWARE

Well-known programs include Astroart, MaxIm DL (below) and Nebulosity COLOUR CAMERA

Use a DSLR or one-shot colour CCD to capture the colour data IMAGE EDITING SOFTWARE

A layer-based image editing program will allow you to combine your images MONOCHROME CAMERA

Use a monochrome CCD camera with a hydrogen-alpha filter to capture the narrowband data

Combining luminance and RGB data – top left and top right – allowed us to create this much more detailed composite image of the North America Nebula, NGC 7000, in the constellation of Cygnus

STEVE RICHARDS X 7, THINKSTOCK

I

n last month’s How to, we showed you how to assemble and balance two telescopes and two cameras on a single mount to create a dual imaging platform. Now we’re going to explain how to capture images using this setup and combine them. The exact process depends on what two cameras you are using, but in all cases you need to adjust the orientation of both so that they closely match one another, and take bias, dark and flat calibration frames as appropriate for all sets of data.

skyatnightmagazine.com 2013

Suppose you are using one colour camera and one monochrome camera. The colour camera collects red, green and blue (RGB) data as expected, but you have three options for how you use the monochrome camera. The first is to add a luminance filter so you collect luminance (L) data. This adds overall detail to the colour image and works well for all celestial objects. Alternatively you could capture narrowband data using hydrogen-alpha (Ha), Oxygen III (OIII) and Sulphur II (SII) filters to produce a totally different false-colour image of the same object,

or a Ha filter alone to enhance the red data from the colour camera. The last two options work very well when imaging emission and planetary nebulae.

Camera combinations If you have two colour cameras in the setup, you double your data collection. The extra image frames will produce a smoother colour image and reveal more detail too. Calibrate and stack the data from each set of frames into two master frames, then stack the two master frames to produce the final image. Two monochrome

SKILLS APRIL 81

cameras, on the other hand, give you the most flexibility – you could use one camera with a set of RGB filters to generate a colour image while you collect luminance data with the other camera, or alternatively collect different narrowband data at the same time to create effective bi-colour images.

STEP-BY-STEP GUIDE

Start the right way There’s a simple rule to apply if the image resolution between the two camera and telescope combinations doesn’t match – the camera that sets the finished size is the one used to take the luminance data for a standard colour image, or the one used to take the hydrogen-alpha data for a hybrid RGB and narrowband image. This is because this data holds the main image detail and shouldn’t be resized, whereas the colour data can be reduced or enlarged to match without any serious loss of fidelity. Let’s assume you’re using a monochrome CCD with a hydrogen-alpha filter and a one-shot colour CCD camera (though you’ll get the same results using a second monochrome CCD with RGB filters). Choose a suitable hydrogen-alpha emission object. Once you have captured, calibrated and stacked your data, you will end up with two image files, one containing the hydrogen-alpha data and the other the RGB colour data. These two images should be carefully processed using the Levels and Curves adjustment tools so that they become attractive images in their own right. Save each one as a 16-bit TIFF file. Using astronomical imaging software such as RegiStar or MaxIm DL, align the two images. You should use the hydrogenalpha image as the ‘reference’ image – in other words, the image that the colour image will be adjusted to in order to match for size and orientation. Save the adjusted colour data under a new name. Load both images into an image editing program such as Photoshop or GIMP, then select the colour image and view its channels. Select the red channel, copy it to the clipboard and paste it into a new file. Swap to the hydrogen-alpha image, copy it to the clipboard and paste it on top of the extracted red channel. Adjust the opacity of the top layer until you get a nice mix of the two and flatten them so they become one layer. Paste it into the red channel of the original colour image. You now have a hydrogen-alpha enhanced red channel, which shows more detail than the original colour image. S

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

STEP 6

Choose an alignment star near the object that you want to image, centre it in the field of view and accept the alignment. With a Bahtinov mask in place, take a series of test images and focus the star. Now focus the second telescope in the same manner.

Take a set of bias, dark and flat frames for each set of data and calibrate the captured images. De-Bayer (convert to colour) the RGB images before stacking them. Save the final RGB and hydrogen-alpha images as 16-bit TIFFs.

Using the Layers and Channels functions in your image processing software, combine the two images. Do this by pasting the hydrogenalpha image on top of a copy of the red channel extracted from the RGB colour data and adjust the opacity to about 40 per cent.

With the test sequence still running, carefully align one telescope (the one with the smallest field of view if they are different) on the object that you want to capture and set an imaging sequence running. Set a second sequence running on the second telescope.

Rotate and resize the larger of the two images (if there is one) using suitable software like RegiStar or MaxIm DL so that the two images align perfectly with one another. Save the adjusted image as a 16-bit TIFF under a new name.

Merge the new ‘red’ data, then copy and paste it into the red channel of the RGB image. Gently stretch the image using the Levels and Curves adjustment tools to bring out the detail. Tweak the colour balance and saturation to taste.

skyatnightmagazine.com 2013

Physics and Our Universe: How It All Works Taught by Professor Richard Wolfson lecture tit es

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IM ED T E OF IT

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1. 2. 3. 4. 5. 6. 7. 8.

The Fundamental Science Languages of Physics Describing Motion Falling Freely It’s a 3-D World! Going in Circles Causes of Motion Using Newton’s Laws—1-D Motion 9. Action and Reaction 10. Newton’s Laws in 2 and 3 Dimensions 11. Work and Energy 12. Using Energy Conservation 13. Gravity 14. Systems of Particles 15. Rotational Motion 16. Keeping Still 17. Back and Forth— Oscillatory Motion 18. Making Waves 19. Fluid Statics— The Tip of the Iceberg 20. Fluid Dynamics 21. Heat and Temperature 22. Heat Transfer 23. Matter and Heat 24. The Ideal Gas 25. Heat and Work 26. Entropy—The Second Law of Thermodynamics 27. Consequences of the Second Law 28. A Charged World 29. The Electric Field

30. Electric Potential 31. Electric Energy 32. Electric Current 33. Electric Circuits 34. Magnetism 35. The Origin of Magnetism 36. Electromagnetic Induction 37. Applications of Electromagnetic Induction 38. Magnetic Energy 39. AC/DC 40. Electromagnetic Waves 41. Reflection and Refraction 42. Imaging 43. Wave Optics 44. Cracks in the Classical Picture 45. Earth, Ether, Light 46. Special Relativity 47. Time and Space 48. Space-Time and Mass-Energy 49. General Relativity 50. Introducing the Quantum 51. Atomic Quandaries 52. Wave or Particle? 53. Quantum Mechanics 54. Atoms 55. Molecules and Solids 56. The Atomic Nucleus 57. Energy from the Nucleus 58. The Particle Zoo 59. An Evolving Universe 60. Humble Physics— What We Don’t Know

Physics—Made Clear Physics is the fundamental science. It explains how the universe behaves and gives us an extraordinary power over our world. Which makes physics sound like the most complicated subject there is. But it isn’t. In fact, physics is so simple that anyone with a willingness to learn can grasp its unlimited wonders. In 60 enthralling lectures, Physics and Our Universe: How It All Works proves that case, giving you a robust introduction to physics using nothing more advanced than high-school algebra. Noted physicist and Professor Richard Wolfson’s lectures—intensively illustrated with diagrams, animations, graphs, and other engaging visual aids—introduce you to scores of fundamental ideas related to Newtonian mechanics, oscillations and waves, thermodynamics, electricity and magnetism, optics, quantum theory, and more.

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SKILLS APRIL 83

SKILLS

Sketching Crater Albategnius

With Carol Lakomiak

NEED TO KNOW STEP 1 Carefully draw a basic outline of Albategnius’s main features with an HB pencil, also adding where the shadows are. Fill in the shadows with a 4B pencil. It’s important to draw the shadows now because they move rapidly and can cause confusion as the sketch progresses.

NAME: Crater Albategnius TYPE OF OBJECT: Lunar crater CONSTELLATION: In Cancer on the suggested night RA: N/A DEC.: N/A TIME TO SKETCH: The night of 18 April EQUIPMENT: 4-inch telescope or larger; H, HB, 4B pencils; blending stump; sandpaper; hard and soft art erasers FIELD OF VIEW: 337 square kilometres at 404x magnification

ALL PICTURES: CAROL LAKOMIAK

T

his month’s target is named in honour of Al-Battani, a brilliant astronomer and mathematician whose works were quoted by Nicolaus Copernicus and Tycho Brahe among others. He lived from 858 to 929 in Upper Mesopotamia, an area that straddles what is now northwest Iraq, northeast Syria and southeast Turkey. One of his most famous astronomy achievements was determining the length of a year to within a few minutes of our modern calculations. Crater Albategnius is located in the central highlands of the Moon’s southern hemisphere. It contains a few northern craters and a central peak, and is overlapped by Crater Klein on its southwest wall. It’s easy to get carried away when making a lunar sketch, so study Albategnius in the eyepiece for a while in order to determine how much of it you want to sketch and which features to include. While doing this, you’ll notice that sunlight reflects more brightly from some areas than others – this is the ‘albedo’ mentioned in steps two and three. On the suggested sketching night, the Moon will have reached its highest point

just before sunset, so the earlier you can start sketching the better. You can even begin before sunset if you’d like. The view won’t be the best, but it will be sufficient enough to get the basic outline completed. If you begin before sunset though, don’t draw the shadows until you can see their edges quite clearly. Since Albategnius’s central peak is centrally located, begin there and work your way around, judging each feature’s shape and placement as accurately as possible. When drawing your basic sketch, be sure to include the borderlines of bright areas on the walls of both Albategnius and Klein. To remove the lines later, work a soft eraser to a point and dab off as much of the graphite as possible. Then with a blending stump, use small circular motions to blend any residual lines into the sketch. Some final tips. If an area seems a bit dark, flatten a soft eraser and dab layers of graphite from the sketch until the albedo is adjusted. Finally, clean any stray smudges from bright albedo areas with the corner of a hard eraser.

STEP 2 Draw the darker of the albedo areas by holding your HB pencil flat against the paper, then use a blending stump to gently push the graphite into the paper’s texture. The blending process will make the graphite appear darker, so be sure to use it sparingly.

STEP 3 Clean the blending stump on piece of sandpaper. Using an H pencil, apply the lighter albedo areas with the same technique as in Step 2. Brighten the white areas with a hard eraser. If necessary, remove excess graphite with a soft art eraser.

skyatnightmagazine.com 2013

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SKILLS APRIL 85

SKILLS

SCOPE

doctor

Our resident equipment specialist Steve Richards cures your optical ailments

For DSLR astrophotography, do I need an adaptor that screws onto a lens’s filter thread and then connects to the scope, or a T-ring and adaptor that replaces the lens?

STEVE RICHARDS X 2/TAKEN FROM THE BOOK: MAKING EVERY PHOTON COUNT

MARK WILLIAMS

It is not possible to screw a DSLR lens directly onto a telescope. There are essentially two ways of using a DSLR camera with a scope, and which one you use depends on the type of object that you want to image. The conventional method is what is known as prime focus imaging. This method involves connecting the camera body, without a lens, directly to the telescope’s focus tube – turning the scope into another interchangeable lens for the camera. You need a ‘T-ring’ to do this. It has a 42mm female thread at one end and a camera-specific mounting at the other end. Some telescopes have a matching male T thread on their focus tubes, but those that don’t can use a ‘T to 1.25-inch’ (or 2-inch) nosepiece, which push-fits into the eyepiece holder. Prime focus The T-ring, below, screws into your DSLR; if your scope doesn’t have a matching thread you’ll also need a T nosepiece, right, to link the two

imaging with a DSLR is well suited to capturing deep-sky objects, which are generally large, thus requiring less magnification. A lesser used method to ‘connect’ a DSLR is afocal imaging, which is where you simply aim the camera down the eyepiece of the telescope. Afocal imaging is normally used to increase magnification, which is achieved by projecting the light from an eyepiece inserted into the scope’s focuser into a DSLR camera’s lens. This method can work quite well for lunar images and to a lesser extent planetary images, although a high frame rate camera or a webcam will capture far better results of both targets.

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

collimation? Is there soft ware that can help with you may find There are two software packages that ires a video requ but free, is 5.0 e useful. MetaGuid ting with assis capture device to operate. As well as sure mea e, guid auto collimation, the software will odic peri log and t men align seeing, assist with drift from ded nloa dow be can ram prog error data. The . ww.astrogeeks.com/Bliss/MetaGuide to be The other is CCDInspector, which has is a very it but d, perio trial ay paid for after a 30-d ing help as well As tool. lysis ana e comprehensiv of e rang with collimation, it measures a wide camera. parameters using your imaging CCD from ded nloa dow The software can be pector. www.ccdware.com/products/ccdins

I have a 12-inch Sky-Watcher Newtonian Go-To telescope. What are the best eyepieces for observing Saturn, Jupiter and deep-sky objects? GEOFF WADSLEY

The requirements for planetary and deep-sky observing are very different, with the planets needing higher magnifications than nebulae and galaxies. Your telescope has a focal length of 1,500mm and a fast focal ratio of f/4.9. Typical planetary eyepieces for this scope would be in the 5mm to 8mm focal length range, yielding a maximum magnification of 300x. For deep-sky observing a set of eyepieces covering roughly 12mm to 30mm would be ideal. With a fast telescope like yours, the eyepieces need to be chosen carefully to maintain good sharpness and star shapes around the edge of the field. Good choices for planetary observation include the TeleVue Ethos 6mm, TeleVue Delos 6mm, Pentax XW 5mm or Sky-Watcher Nirvana 7mm. For deep-sky the Pentax XW 14mm, 20mm and 30mm, and Sky-Watcher Nirvana 16mm and 28mm would be excellent.

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

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SKILLS APRIL 87

SKILLS

LOST IN The trials and tribulations of a novice astronomer

With Keith Hopcroft

Y

ou join me smack in the middle of an existential crisis. I don’t know the correct collective noun for neuroses – a constellation, a cluster, a galaxy? – but whatever it is, that’s what I’m suffering. Or, if you prefer to have my breakdown deconstructed: guilt, anxiety and phobia. Guilt because I’ve not taken my refractor out for a slew for what feels like a main-sequence lifetime. I’ve been so rubbish that I’m not sure I can legitimately call myself an amateur astronomer anymore. My telescope is in danger of becoming just another object which, instead of defining me, racks me with remorse – like my tennis racket, my guitar and my lawnmower. Less so the lawnmower. Anxiety because, suddenly, there’s an implausible conjunction of: a clear night sky; wife asleep; nothing on telly; no chores; and a sudden spurt of enthusiasm. Which means that, yes, tonight’s the night for some stargazing. Which is fine, except the pessimist/neurotic in me agitates that I probably left my finderscope on last time, or that I forgot to charge the power pack. Besides, it’s been so long that the tectonic plates will have shifted, meaning I’m now unsure what coordinates to enter into my hand controller. Phobia? Ah, that’ll be the spiders. Despite the dust sheet, my scope is covered in arachnids and their webs, a damning picture of astro-neglect. In truth, I’m not really spider phobic. But I am phobic of the effect they might have had on my telescope. Nasty spidery marks on the precious

lenses, or nasty spidery bodies clogging up the gear mechanism. My eight-legged tenants complete my psychosis by lodging that Ziggy Stardust song in my head on a loop. Undaunted, I set up. Or, rather, I dust off, evict, wipe down and set up. I grit my teeth

Hello cosmos, I’m back. And it’s like I’ve never been away: the chill of the night air slowly numbing my fingertips as I focus on old favourites. Fantastic views of the Beehive Cluster in Cancer, splitting the binary star Castor in Gemini, a quick hop to nearby M35... it all comes flooding back. Amazing. And to think I neglected all this for The Great British Bake Off. I finish the evening with a glorious and lingering view of Jupiter, belts and all. Despite my angst, there’s not a spider in sight. Mind you, I haven’t looked at Mars.

WILL HOPCROFT, ILLUSTRATION BY JEFF PARKER

“It comes flooding back. And to think I neglected this for The Great British Bake Off” and wait for bad things to happen. That’s odd. The finderscope is fine. And the battery’s fully charged. The scope is working! I can even dimly recall the names of two visible stars to complete the auto align.

Keith Hopcroft is a GP and a columnist for The Times

skyatnightmagazine.com 2013

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REVIEWS APRIL 89

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

94

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

Discover how Revelation’s larger, 25x100 binoculars could change your view of the night skies

PAUL WHITFIELD X 3, THINKSTOCK

This month’s reviews

First light

90

iOptron Smart EQ Pro equatorial Go-To mount

94

Revelation 25x100 pair of binoculars

98

StarTools image processing software

Books

Gear

102

104

We rate five of the latest astronomy titles

Including this reddot finderscope

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

90

FIRST light iOptron Smart EQ Pro

Go-To mount

SKY SAYS… When tracking, the mount kept each object centred in the field of view for well over 75 minutes

This lightweight mount has a low load capacity but offers great portability – and an added benefit for trips south of the equator WORDS: STEVE RICHARDS

VITAL STATS • Price £449.99 • Load capacity 5kg • Hand controller Go2Nova 8408 • Database 59,000 objects • Flash upgradeable Yes • Autoguider port ST4 • Tripod 1.25-inch tubular steel legs • Weight Mount 2.8kg (excluding counterweights), tripod 2.6kg • Supplier Altair Astro • www.altairastro.com • Tel 01263 731505

T

he iOptron Smart EQ Pro is billed as a super-portable equatorial mount and, weighing just 5.4kg all in all, it is certainly that. The mount head weighs 2.8kg without counterweights and is an unusual rectangular shape, finished in a mix of cream alloy sections for strength and matching coloured plastic for finishing trim. Two black plastic panels, one each side of the head, reveal compartments for eight AA batteries, though there is also a 12V external power socket. Two RJ11-style sockets complete the connections – one marked ‘HBX’ that allows you to connect the Go2Nova hand controller and an identical but unmarked socket that provides the industry standard ST4 autoguiding port. The mount is supplied with a quick start manual, although a comprehensive PDF manual is available for download. iOptron’s excellent illuminated polarscope is pre-installed on this mount, though there is a minor design issue here in that if you use the mount at a latitude of 50 º or greater, you can’t remove the polarscope cap as it is blocked by the latitude adjustment bolt – the cap must be removed in advance. The tripod is also lightweight (2.6kg) and certainly helps with the ‘grab and go’ aspect of the mount, although we did find that the plastic locking collars for height adjustment introduced a little more flex than we would have liked.

PAUL WHITFIELD X 2, STEVE RICHARDS

DESIGNED WITH CUNNING The whole ethos behind this mount is its grab and go nature, which is not that easy to achieve with a fully functional equatorial Go-To. However, the careful choice of materials and attention to detail in the design has produced a mount that meets these aims. The sturdy, box-shaped aluminium housing has been cunningly designed so that much of the mass of the gears and motors resides on the counterweight side

skyatnightmagazine.com 2013

of the RA axis. This has the effect of shifting the centre of gravity of this axis in the right direction to minimise the counterbalance weight required to offset the telescope itself, which is conveniently mounted very close to the RA axis. The two side pods that store the eight AA batteries for the built-in power supply also provide some counterbalance. The lightweight steel tube tripod completes the package by giving reasonable stability.

With the clutch disengaged, the RA axis rotates very freely, making the mount easy to balance, but the dec. axis was stiff in comparison and it was more difficult to assess the correct balance point. However, the iOptron manual states that balance in the dec. axis is not critical because of the low load capacity of this mount. It was a good match for our William Optics Megrez 72 refractor. Balancing it required the single 0.9kg counterweight, supplied as standard, to be placed at the maximum extension of the retractable counterbalance bar.

Have mount, will travel Polar alignment was simple and straightforward with the assistance of the hand controller, which displayed a circular ‘clock’ showing the position of the star Polaris at our local time and location. It was a simple matter to adjust the altitude and azimuth bolts on the mount until the view through the polarscope matched that of the hand controller. Users in the southern hemisphere would find it equally simple to use the hand controller display to show the position of the star Sigma Octantis. Combined with the grab and go features of the mount, this makes it an excellent travelling companion for astronomy holidays in both hemispheres. >

FIRST LIGHT APRIL 91

VIXEN-STYLE MOUNTING BLOCK The substantial, cast Vixen-style mounting block suits the design of the mount well as typical telescopes suitable for this mount – small refractors and small reflectors – will be equipped with a matching dovetail bar. The single retaining bolt held our dovetail shoe very securely and the elliptical locking knob was easy to grip when wearing gloves.

HAND CONTROLLER The Go2Nova 8408 hand controller supplied with the mount has a back-up battery that automatically updates the date and time. Unusually, this controller has a four-line display, which shows more data than conventional models. A very comprehensive database of 59,000 objects ensures a ready supply of celestial delights for all occasions.

TRIPOD The lightweight tripod has 1.25-inch tubular steel legs. These are extendable, providing a range of heights from 62cm to 106cm, making the mount suitable for both small refractors and reflectors. The built-in fold away leg spreader has a neat clip-in plastic tray with three receptacles to hold 1.25-inch eyepieces.

skyatnightmagazine.com 2013

92 FIRST LIGHT APRIL

FIRST light

BATTERY BOXES Ultra portable mounts like this are designed to be taken to dark observing sites, so minimising the amount of equipment you need to take with you makes good sense. The conveniently placed battery pods mean that an external power supply is not required as the mount is completely self contained.

POLARSCOPE The illuminated polarscope is unusual as it has a reticule with two sets of engraved circles on it. The inner set are for use in the northern hemisphere, to align the mount with Polaris, while the outer set are for use south of the equator to align to the southern hemisphere pole star, Sigma Octantis.

> You have a choice of one-, two- or three-star

SKY SAYS… Now add these: 1. Altair Lightwave 60mm refractor

ALL PHOTOS: PAUL WHITFIELD

2. Eight AA batteries 3. Altair Miniguider 60mm guiding system

alignment, the Go-To accuracy improving with the number of alignment stars used. For most of our sessions we chose the three-star alignment option, which helps to alleviate the problem of cone error – a pointing error that occurs if the telescope is not mounted at exactly 90 º to the RA axis. This alignment method worked very well, ensuring that all our subsequently chosen objects appeared comfortably within the view of our 17mm eyepiece. However, using one-star alignment also produced perfectly acceptable Go-To results with our short focal length (432mm) refractor. When tracking, the mount kept each object centred in the field of view for well over 75 minutes – after which we abandoned this test as it clearly passed with flying colours. If you don’t want to use the Go-To system and hand controller at all, the mount can be manually pointed at any object and then, when the power switch is turned on, it will track quite happily at sidereal rate with no controller attached. We very much enjoyed our time with this mount as it was light to carry, easy to set up and polar align, produced good Go-To results and tracked well. We certainly felt that it achieved its portability goals easily as well as making for an excellent beginner’s mount. S

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

★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★

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Eyepieces & Accessories EYEPIECES/ACCESSORIES Plossl 5mm (1.25î)................................................................. £14.99 Plossl 10mm (1.25î) .............................................................. £14.99 Plossl 15mm (1.25î) .............................................................. £14.99 Plossl 20mm (1.25î) .............................................................. £14.99 Plossl 25mm (1.25î) .............................................................. £17.99 Plossl 30mm (1.25î) .............................................................. £17.99 Plossl 40mm (1.25î) ............................................................. £19.99 Super Wide angle 10mm (1.25î) ....................................... £39.99 Super Wide angle 20mm (1.25î) ....................................... £44.99 FF 8mm (1.25î)....................................................................... £49.99 FF 12mm (1.25î) .................................................................... £49.99 FF 19mm (1.25î) .................................................................... £49.99 FF 27mm (1.25î) .................................................................... £49.99 SWA 26mm (2î) ..................................................................... £79.99 SWA 32mm (2î) ..................................................................... £79.99 SWA 38mm (2î) ..................................................................... £79.99 SWA82 8.8mm (1.25î) ...................................................... £129.99 SWA82 14mm (1.25î) ....................................................... £149.99 SWA82 24mm (2î) ............................................................. £199.99

102 ED

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94

FIRST light Revelation 25x100

binoculars Offering four times the light grasp of 10x50s, these binoculars have good deep-sky potential WORDS: PAUL MONEY

VITAL STATS • Price £210 • Optics Fully multicoated • Aperture 100mm • Magnification 25x • Prisms BAK-4 Porro • Angular field of view 2.5º • Focusing Individual eyepiece focusing • Exit pupil 4mm • Eye relief 15mm • Weight 3.8kg • Supplier Telescope House • www.telescopehouse. com • Tel 01342 837098

E

xploring the wonders of the night sky with binoculars is highly rewarding, but there are occasions when 10x50s can seem a little lacking. If you yearn for something a bit more powerful, a pair of 25x100 binoculars could be for you. Covered in black, easy to grip leatherette, Revelation’s 25x100s have independently focusable eyepieces and rubber eye guards. Front and rear protective caps and a hard case complete the package. One slight downside is that the end faces of the two prism housings are reflective silver, an odd choice for something to be used at night. What you gain in increased magnification and light grasp you pay for with increased weight. These binoculars check in at 3.8kg, so it’s not easy to hold them by hand for long periods. This is why the design includes a central bar with a sliding tripod adaptor – you can attach these binoculars to any standard photographic tripod to take the strain out of using them. By adjusting the centre of balance along the bar, we were able to find a sweet spot that allowed us to tilt the tripod head at quite a steep angle.

OPTICS The 4-inch main lenses gave a clear view of a variety of objects, from Jupiter and its moons to galaxies and nebulae, and offered excellent light grasp. These lenses are also fully multicoated, which helps to make deep-sky objects look clearer.

ALL PHOTOS: PAUL WHITFIELD

Surveying the sky SKY SAYS… The interpupillary distance was smooth to adjust and it was easy to focus each eyepiece independently until we were happy with the view

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To get the best out of any binoculars you need to make sure you set the interpupillary distance between the eyepieces to match your own eyes. We found this smooth to adjust, although we would have liked to see an engraved scale so we could remember our spacing. Focusing is also critical and it was easy to refine each eyepiece independently until we were happy with the view. Turning to the night sky, we aimed the binoculars at Capella, the alpha star in the constellation of Auriga – and were rewarded with a crisp image across 85 per cent of the 2.5º field of view, with only the slightest trailing off in quality towards the edges. Jupiter was bright at the time of review and the binoculars showed a small disc, not quite big enough for bands to be easily seen, but the four Galilean moons stood out a treat. Scanning across >

INTERNAL BAFFLING The internal baffles did their job and reduced the reflections that can cause light scatter in the optics and degrade the view. There was, however, a little colour fringing on the Moon and Jupiter.

FIRST LIGHT APRIL 95

CATCHING THOSE PHOTONS On its own, a 4-inch (100mm) refractor with a multicoated main lens can give enjoyable views of many deep-sky objects, but put two together to form binoculars and the light grasp of each combines to bring the night sky alive. These 25x100 binoculars collect four times as much light compared to more common 10x50s. The 25x magnification and 2.5º field allow large objects such as the Andromeda Galaxy and the Sword of Orion to almost fill the view. The main lenses are fully multicoated to prevent light scattering off the front of them, so you benefit as they are able to collect more light. The optics also demonstrated good contrast, which helped diffuse deep-sky objects such as the Crab Nebula and galaxy NGC 2903 in Leo to stand out well.

CENTRAL BAR WITH TRIPOD ADAPTOR At 3.8kg, these binoculars are too heavy to hold by hand for long periods. This central bar with its sliding adaptor allows you to attach the binoculars to a tripod. You can adjust this to find the best balance point and add the stability you need for a good viewing experience.

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96 FIRST LIGHT APRIL

FIRST light EYECUPS Stray light can reduce the contrast of a view, especially when it comes to deep-sky objects. The rubber eyecups worked well to reduce any external reflections and although a little stiff they can also be folded back, so if you wear glasses you can still enjoy the full view.

FOCUSING AND INTERPUPILLARY ADJUSTMENT Focusing the individual eyepieces was smooth and gave good control over the focus, which is critical for getting the best out of binoculars. The interpupillary adjustment between the two eyepieces had a good range and it was relatively easy to adjust to merge the two views into one.

SKY SAYS… Now add these: 1. Horizon heavy-duty tripod

ALL PICTURES: PAUL WHITFIELD

2. Philip’s Stargazing with binoculars 3. Orion StarSeek 3 smartphone app

skyatnightmagazine.com 2013

> to Aldebaran and the Hyades star cluster, both in Taurus, the view was delightful, although we couldn’t fit all of the cluster stars into the field at once. We also saw dwarf planet Ceres and asteroid 4 Vesta – we estimate that there are several dozen asteroids within reach of these binoculars, depending on your eyesight. Before we left the region we checked out the Pleiades open cluster and counted 105 stars, the fainter ones with averted vision. Spotting the subtle glow of the Merope Nebula was a bonus. Farther afield, we saw a stunning amount of nebulosity in the Orion Nebula, with wisps of gas curving away from the Trapezium cluster at its centre. Casting our gaze higher, the star clouds of the winter Milky Way were impressive while the Double Cluster in Perseus sparkled like diamond. We also hunted out several galaxies, including interacting pair M81 and M82 in Ursa Major, which appeared as bright smudges hanging among the stars. The 2.5º field of view worked

in our favour when we turned to the Andromeda Galaxy – we were able to see the large central bulge, two spiral arms around it, and companion galaxies M32 and M110. The waxing Moon showed a small disc due to the wide field. Our view was crisp along the terminator, although we did notice a slight amount of colour fringing around the Moon’s edges. But while the views of the Solar System could have been a little crisper, when it came to the rich treasure trove of deep-sky objects they did a great job. S

VERDICT BUILD AND DESIGN EASE OF USE EYE RELIEF FEATURES OPTICS OVERALL

★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★

Lamb Observatories Personal Viewing Environments for Astronomers Wooden Roll Off Roof Skyshed Observatory Manufacturers and Installers UK wide. Standard Skyshed models range from: 6’ x 6’ Remote Imaging set up and leave version through to 16’ x 10’ Observing+Control/Warm Room Skyshed. A bespoke service is also available. Visit our website for full specifications and prices. Observatory Relocation Service - please contact us for details. Customer focused guidance and assistance provided throughout to ensure your Skyshed layout and design fully meets your Observing needs.

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98

FIRST light

StarTools

SKY SAYS… StarTools is useful for processing deep-sky and Solar System images alike, and can make a real difference to how they look

Image

processing

software

TRACK The Track option can be used with images that are to be processed from scratch – it doesn’t work if the image has been pre-processed (stretched) before loading into StarTools. Track can monitor what’s been done to the image, so that, for example, functions that reduce noise will take previous processing steps into consideration.

Look past its oddly named functions and this computer program makes a refreshing change WORDS: PETE LAWRENCE

THINKSTOCK, PETE LAWRENCE X 3

VITAL STATS • Price A$60 (approx £43) • System requirements Small datasets (less than one million pixels): 32-bit Windows, Pentium 4 processor with 512MB RAM; or MacOSX Tiger (10.4) and Mac Intel processor Large datasets (more than 12 million pixels): 64-bit Windows, quad-core or greater processor, 16GB RAM; not recommended for MacOSX • Input file formats FITS, TIFF (IBM PC byte order format) and PNG • Output file formats 16-bit TIFF • Demo version Available through website, save function inhibited • Updates Licence allows you to download updates for two years from purchase date • Developer Ivo Jager • www.startools.org

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W

here astrophotography is concerned, the myriad of image processing functions that you can apply to your shots of the night sky can be overwhelming, especially if you’re a beginner. For experienced imagers, applying basic tweaks becomes second nature, but wandering off track and into new territory can take effort. StarTools is an image processing application that offers a refreshingly different approach. Underneath its simple front interface is a powerhouse of tools. You won’t find core functions such as levels and curves here, but rather more powerful routines that encapsulate the more basic functions. It’s worth pointing out that StarTools doesn’t stack, register or calibrate images: you’ll need something else to do that. This program is designed to be used afterwards to help produce a polished end result. The interface is clean and easy to get to grips with. Among the 24 main functions are a few simple tidying up routines such as Mirror, Rotate and Crop. Mixed in with them are less obvious functions such as Synth, Develop and Life – more about those in moment. On our first outing we had no idea what these did, but a simple yet effective help system is there to guide you.

Minor irks The program can only open FITS, TIFF (IBM PC byte order format) and PNG files, chosen because these formats do not discard data when images are saved as them. Although the reasons for this restricted set are valid, we couldn’t help but think that offering JPEG compatibility, with a suitable warning about lower quality, might give the program broader appeal. All files have to be saved as TIFFs. StarTools is generally fast, and when it does need to think about something it warns you and requests you press a button to continue. It can be operated on low-power machines, but the more powerful your >

>

FIRST LIGHT APRIL 99

INTERFACE The StarTools interface is clean, quick and efficient. The main functions are arranged in a 2x12 grid on the left. General functions such as Open, Save, Keep and Cancel appear, when relevant, along the top of the main window. When a main function is in use, additional option sliders and switches are presented along the bottom of the window.

DEVELOP The Develop function is a great starting point, especially for deep-sky images. As its name suggests, it’s used to ‘develop’ an image to bring out hidden detail. Unlike its more basic relatives such as levels and curves, Develop won’t clip an image unless you deliberately want to. Clipping creates black and white areas, losing parts of the image in the process.

A FRESH APPROACH TO IMAGE PROCESSING There are many clever things about StarTools, but the most impressive is the way that it rejuvenates image processing by combining more primitive algorithms into new routines. These new functions are very powerful, well implemented and are relatively easy to get to grips with if you’re new to image processing. Where appropriate, suboptions appear when a main function has been selected and these allow you to tweak settings to suit your taste. Many show immediate changes as, say, a slider is adjusted. Others require you to ‘action’ the change once a new setting has been made.

To help you on your way, some of the main functions also include intelligent presets. For example the HDR function offers presets called Optimise, Equalise, Tame and Reveal, all of which change the settings for the HDR function in a different way. Simply click on each preset to see what changes it produces. It’s quite understandable to be put off by the unfamiliar function names. However, we’d heartily recommend just trying each one to see what it does. Before long, functions such as Magic, Flux, Heal and Develop will become second nature.

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100 FIRST LIGHT APRIL

FIRST light Decon (deconvolution) function really helped us to reveal small details in images of the lunar surface and high-resolution shots of Jupiter, while the Synth function allows you to touch up your stars. It considers the effect your scope has on the shape of stars and can model what your image’s stars should look like – you then have various options on how to blend artificial and real stars together.

Deep processing

IMAGE PROCESSING FUNCTIONS Many of the main functions offer option presets, which are displayed along the top of the screen. These apply setting values to the configurable options along the bottom of the screen. Undo/Redo gets you out of trouble and a Before/After toggle lets you see exactly what difference the last process made.

SKY SAYS… Now add these: 1. DeepSkyStacker 2. GIMP 3. RegiStax

> computer, the better your experience will be. On Macs, the program is limited to lower-power 32-bit mode, though future updates will address this. StarTools is at its most powerful when the image you want to work on hasn’t been stretched in any way to bring out faint detail. A clever tracking mode keeps a record of all processes previously applied; for example, if you use a routine that works on reducing image noise, the program takes all previous processing steps into consideration. This helps keep the noise reduction as faithful as possible. We gave the software a good workout using a variety of Solar System and deep-sky images. The

Many of the functions can adjust an image in a visually dramatic way, but the adage less is more still applies here. Contrast and HDR (high dynamic range) really helped to bring out the best in our deep-sky test shots. HDR is great at recovering almost overexposed features such as you’d find in the centre of, say, the Orion Nebula. The Life function is well named. Apply this to an image and it’s possible to make it look dramatically vibrant. We used it on a narrowband Hubble-palette image of the Rosette Nebula and it really allowed us to emphasise the beauty of the nebula without making it appear unnatural or false. Meanwhile, the Wipe function analyses an image and gives you various options to reduce unwanted vignetting and gradients. Like many of the other functions presented, selecting Wipe brings up a number of sub-options that can be adjusted to tweak the application of the main Wipe function. We were quite impressed by StarTools. It’s useful for deep-sky and Solar System images alike, and can make a real difference to how they look. Like the Life function does to images, StarTools offers a breath of fresh air in a field that at times can be complex and bewildering. S

VERDICT FUNCTION RANGE INPUT COMPATIBILITY OPERATION OUTPUT QUALITY SPEED OVERALL

★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★ ★★★★★

MASK PETE LAWRENCE X 2

Many functions attempt to do things that may not be good for certain parts of an image – for example, the stars themselves. A mask can be defined to either select or deselect these regions. Using stars as an example, it’s possible to automatically select them and then invert that selection so that all stars are unaffected by your edits.

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102

Books New astronomy and space titles reviewed

Searching African Skies

SKA ORGANISATION/TDP/DRAO/SWINBURNE ASTRONOMY PRODUCTIONS

Sarah Wild Jacana £26.50  PB The Square Kilometre Array (SKA) will revolutionise radio astronomy. This mammoth telescope, soon to be built in South Africa and Australia, will have up to 4,000 separate radio antennas spread over an area about 3,000 kilometres across. for smaller, more sensitive regions there Linked by optical fibres to a hugely powerful are important issues to be addressed. The SKA will be built at the heart of not one, supercomputer, the array’s sensitivity will but two remote and rural environments be 50 times greater than anything in – so it may be the first big science project operation today. Naturally, there is great to have a significant effect on its hosts. interest in the instrument, its technology Wild rightly spends some time on these and its scientific capabilities. socioeconomic aspects – what In this book, Sarah Wild the SKA means for South investigates how South Africa – but when Africa, previously a quiet discussing its main backwater in the radio scientific objectives, astronomy world, Wild’s treatment came to be a occupies a single, dominant player in rather short, chapter. the bid to host the Furthermore, SKA. It is an although some interesting story and mention is made one worthy of being of the technological told. Although the text developments required, is occasionally disjointed these discussions concentrate and a little too personal, on the politics of international Wild has done her research Scientists hope that the array will help us collaboration and job creation. well and does a good job understand dark energy While this may not be a at describing the steps book about astronomy (or astronomical toward South Africa’s success in technology), it is still an insightful and co-hosting the facility. interesting read on a topic not previously In the contemporary environment of dealt with in print. ‘big science’ facilities (such as the Large Hadron Collider) we are used to the ★★★★★ deployment of large infrastructure in the wider world. We rarely give a thought ALASTAIR GUNN is a radio astronomer to the benefits or disadvantages that at Jodrell Bank Observatory in Cheshire such projects imbue on their ‘host’ communities. This may not be an issue Reader price £26.50, subscriber price £26.50 in more populous areas of the world, but P&P £1.99 Code: S0413/1 skyatnightmagazine.com 2013

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

2 MINUTES WITH SARAH WILD What inspired you to write this book? The SKA is one of the major science stories in the world today and it is happening in South Africa. Yet most South Africans had no idea what it was about and some didn’t even know that it was happening. I wanted to write a book explaining this amazing project for people who weren’t scientists. Why is South Africa such a good place for astronomy? Radio signals from mobiles, cars and power lines are the anathema of radio telescopes, so many developed countries have too much noise and radio pollution for them. South Africa is less developed, less densely inhabited and is flanked by oceans, so it is ideal. The Northern Cape, where the core site will be, is at high altitude, has unpolluted skies and low rainfall – a radio astronomer’s dream. Did anything surprise you while you were researching the book? I knew that South Africa had a history in astronomy, but I hadn’t realised the extent of it. It was from here that Thomas Henderson first measured the distance to a star using parallax, for example. What part of the SKA’s science are you most excited about? There are three things to look out for: the things we think we’re going to find (dark matter, dark energy, how galaxies are formed), the technological spin-offs (like super-fast computing) and the unknown. I’m interested in serendipity, and finding the things that we didn’t know that we didn’t know. SARAH WILD is science and tech editor of South African newspaper Business Day

BOOKS APRIL 103

The Particle at the End of the Universe K Sean Carroll Oneworld £16.99  HB

O BO F TH E

O N TH MO

You may have noticed words such as ‘boson’ pop up in mainstream papers last year, accompanied by some confused explanations. For those who do not have a particle physicist on hand to translate, Sean Carroll, who happens to be one, has written this book about the finding of the Higgs boson and what it means. Taking the finding as a starting point, the book jets backwards and forwards to focus on crucial elements in the discovery of the elusive particle. Descriptions of the personalities involved and the truly awesome engineering of the experiment itself rub shoulders with the less alluring but crucial matters of statistical analysis

The International Atlas of Mars Exploration Philip J Stooke Cambridge £84.99  HB Philip Stooke is an extraterrestrial cartographer – he makes maps of other worlds. When you think about it, this is an almost fantastical-sounding job. In fact, it has only become possible in the past few decades. In his atlas, Stooke pulls together information from the robotic missions – first fly-bys, then orbiters, landers and now rovers – that have been our surrogate eyes for exploring the alien face of Mars close up. This is a wonderful resource for armchair explorers. It shows how over time we’ve resolved Mars from a fuzzy disc of darker and lighter patches in Herschel’s first telescope-based map of 1784 to an

and how the maths tells us what we should be looking for. This gives a truly admirable and thorough portrait of not just the Higgs hunt, but the massive enterprise of modern research. Carroll’s enthusiasm for his subject means that he occasionally gets carried away and ends up giving explanations that make things more complicated, not less, but most of the time he is clear, even chatty. A section on the implications of the Higgs is a nice addition, including some comments on dark matter and cosmology – as well as the more terrestrial matters of warp drives, truth and beauty, and physics funding. Everything you might want to know about the Higgs boson and the edifice of knowledge that went into finding it is in here. It might be hard to follow in a few places, but particle physics isn’t known for being easy. However, after reading this book you might consider it rather amazing.

★★★★★ KATE OLIVER is a science writer Reader price £15.50, subscriber price £14.50 P&P £1.99 Code: S0413/2

exquisitely diverse world in its own right. It also includes maps of Mars’s two potatoshaped moons, Phobos and Deimos. The discussions on how the touchdown sites for lander missions were decided are also fascinating, explaining the tense balancing act between geographical or engineering constraints and the scientific wish to visit the most interesting locales. But the book curiously limits itself to only the first five decades of Martian exploration, rather than six, omitting the more recent – and more capable – missions. We’ve also mapped Mars in far more ways than just photographs of its surface. For example, we’ve built an incredibly precise altitude map of Mars’s mountains, valleys and craters, and charted the localised magnetic fields, but these are not featured. Also, many of these maps would have benefitted enormously from colour: the Red Planet is all shades of grey in this book.

★★★★★ LEWIS DARTNELL is author of Life in the Universe: A Beginner’s Guide

EXPLORING SPACE Hubble’s Universe Terence Dickinson Firefly  £34.99  HB This stunning book is as good a review of the Hubble Space Telescope’s two decades in operation as you’ll find anywhere. Its pages are filled with many of the images that have made Hubble so renowned, some newly excavated from scientific archives and others reproduced at unprecedented scale across multiple spreads. The crystalclear text outlines the telescope’s technology and development, its greatest discoveries and the variety of objects it has observed. A beautiful and informative tribute.

★★★★★ GILES SPARROW Reader price 32.99, subscriber price £30.99 P&P £1.99 Code: S0413/4

A Down to Earth Guide to the Cosmos Mark Thompson Bantam Press  £16.99  HB Thompson’s relaxed writing style puts the reader at ease as he weaves through the basics of observing the night sky. Monthly synopses of the northern and southern hemisphere skies, complete with simple charts, are interspersed with chapters on specific subjects. These include equipment, the Moon and planets, and the evolution of the Universe, and often reference the work of earlier astronomers. It is an excellent way of introducing concepts to beginners who want to know what’s up there and how to find it.

★★★★★ STEVE RICHARDS Reader price £13.99, subscriber price £12.99 P&P £1.99 Code: S0413/5

Reader price £74.99, subscriber price £72.99 P&P £1.99 Code: S0413/3

skyatnightmagazine.com 2013

104 GEAR APRIL

Gear

Vincent Whiteman rounds up the latest astronomical accessories

1

4 1 Ostara SWA 2-inch eyepiece Price £94.99 • Supplier Northern Optics 01724 782022 • http://northernoptics.co.uk

Fully multicoated, the lens of Ostara’s 26mm, 2-inch super wide-angle eyepiece has a fiveelement construction. It’s also threaded for filters. Two variants – 32mm and 38mm – are available.

2 Nexus WiFi Adaptor

Price £195 • Supplier Equatorial Platforms UK www.equatorial-platforms-uk.co.uk This adaptor lets you control a Go-To mount through planetarium software on your smartphone or other wireless device. It’s compatible with SkySafari3 and Cartes du Ciel among others.

5

3 Green Laser Pointer

Price £32 • Supplier 365 Astronomy 020 3384 5187 • www.365astronomy.com

2

It’s designed to point out constellations and other night-sky objects during tours, but with the flick of a switch this laser pointer becomes a white LED torch – just in case you need a little help navigating closer to home.

4 Compact Zoom Barlow Lens

Price £19.99 • Supplier Nipon Scope and Optics 0844 318 7890 • www.nipon-scope.com This 1.25-inch compact zoom Barlow lens is two accessories in one, giving you the option of 1.5x or 2.5x magnification. It features Bak-4 glass and is multicoated to reduce chromatic aberrations and light reflections.

5 Revelation Astro Smartphone Holder and Digiscoping Bracket

3

Price £48 • Supplier Rother Valley Optics 01909 774521 • www.rothervalleyoptics.co.uk Designed to hold almost all smartphones available, this adaptor clamps over your eyepiece to help you take steady astro photos. The adaptor can also be attached to a tripod.

6 Red-Dot Finderscope

Price £24.99 • Supplier Northern Optics 01724 782022 • www.nothernoptics.co.uk Red-dot finderscopes give a correctly orientated image of the sky – something you won’t get with some optical finders. This one, Optical Hardware’s latest, is fitted with a finderscope shoe.

skyatnightmagazine.com 2013

6

AUTHORS Synopsis and sample chapters welcome, please send to:

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CGC - 33 - 01, 25 Canada Square, Canary Wharf, London, E14 5LQ Te l : 0 2 0 7 0 3 8 8 2 1 2 e d i t o r s @ a u s t i n m a c a u l e y. c o m w w w. a u s t i n m a c a u l e y. c o m All genres welcome

Beginner and advanced advice given. New and second-hand equipment available. TELEPHONE

07799 434030

EMAIL

[email protected]

www. northdowntelescopes. co.uk

ROCKETS & THINGS Supplying all your rocket needs for 12 years & counting. Providing everything you could need to fly rockets.

Rocket motors • Rocket kits Rocket parts • HPR • Recovery Electronics • Ground support Flight support • Literature

We stock… ACME Aerostructures, Aerotech, BSD Rocketery, Cesaroni, DYNA-STAR, Estes Rockets, Fliskits, G-Wiz Flight Computers, JB Weld, LOC Precision, Orbital Engineering, PerfectFlite, Pratt Hobbies, Rebel Rocketery, Rockets & Things, Rowes Retainers and The Launch Pad.

Catch a falling star! Your chance to buy unique jewellery beautifully set with meteorite fragments

Mobile: 07973 545475 | Tel/Fax: 01293 517857 16 Breydon Walk, Furnace Green, Sussex RH10 6RE

www.rocketsandthings.com Increase the efficiency of your reflector by up to 25% Our HI-LUX coating can be applied to almost any reflector, in virtually any condition or no matter how High Reflectivity old. Improves the reflective efficiency of your mirrors. Coating Find out more on our website: Optics > Mirror Recoating or call / email

tech enquiries: [email protected]

Telephone

01782 614200

www.orionoptics.co.uk AWR TECHNOLOGY

INNOVATIVE PRODUCTS • Upgrades for many telescopes giving GOTO performance. • Observatory display units £160. • We do many products to get and keep your telescope working at peak performance. See us at the IAS Show in May

NEW TOOL

Pulse Analyser PA2 Measures pulse lengths for autoguiders.

CONTACT:

01304 365918 www.awrtech.co.uk

106 EXPERT INTERVIEW APRIL

WHAT I REALLY WANT TO KNOW IS…

What makes a green bean galaxy glow? Mischa Schirmer has been probing the inner workings of a new type of galaxy – one that was discovered by accident INTERVIEWED BY PAUL SUTHERLAND

G

alaxies come in many shapes and sizes, depending on such things as their age, environment and any encounters or mergers with other galaxies. But one we discovered in 2010 was unlike any seen before, because it glowed like a bright green bean. We were keen to find out why. Almost all massive galaxies harbour a giant black hole at their centre, with a mass many millions of times more than that of the Sun. These supermassive black holes grow by swallowing nearby gas and stars, creating an accretion disc that spirals down onto the black hole, while at the same time being heated up to millions of degrees. During their most active phases, these feeding black holes – called quasars – can shine 100 times brighter than all the billions of stars in that galaxy together. A strong wind from the central black hole may transport large amounts of gas to the outskirts of the galaxy and beyond. X-ray radiation from the accretion disc also ionises (strips the electrons from) the interstellar gas over several thousand lightyears, making it glow. Clearly the presence of an active supermassive black hole can significantly alter the appearance of a galaxy.

The vibrant hues of green bean galaxies are partly the result of gas being ionised by a central quasar

THINKSTOCK

An intriguing emerald aura The green bean galaxy we found, J2240-0927, showed up by chance in a wide-field image of Aquarius; the shot was taken with the Canada France Hawaii Telescope in Hawaii during a search for galaxy clusters. Its highly unusual colour means that the optical light of this galaxy is not dominated by stars, but by the glow from ionised gas, called ‘nebular emission’. While that is not uncommon in the presence of a quasar or during star formation, the overall level was much higher than has been seen before. Observations with ESO’s Very Large Telescope in Chile showed that the galaxy was 3.7 billion lightyears away, told us its true luminosity (brightness) and gave a detailed view of the emission lines produced. skyatnightmagazine.com 2013

ABOUT MISCHA SCHIRMER Dr Mischa Schirmer is a science fellow at the Gemini Observatory in Chile. His main interest is the study of clusters of galaxies and quasars, and he relaxes by imaging the night sky using homemade telescopes.

We found that essentially all the interstellar gas in J2240-0927 is being ionised by the quasar. Its overall brightness, emitted by (green glowing) double-ionised oxygen, is among the highest ever seen. A similar phenomenon in other galaxies is caused by strong outflows of gas, powered and ionised by a central quasar. However, their spectral characteristics are quite different. If the properties of J2240-0927 were caused entirely by the same phenomenon, we would expect higher gas velocities and lower brightnesses. This led us to think we might be observing a different, new phenomenon, possibly still related to outflows. To find out more, we searched for similar objects to check the activity of their central supermassive black holes. So far we have identified about 20 more green bean galaxies in the Sloan Digital Sky Survey, and confirmed them with spectroscopic observations using the Gemini South Telescope in Chile. We called them ‘green beans’ after the 2007 discovery of ‘green pea galaxies’ by citizen scientists working on the Galaxy Zoo project, but the two cosmic veg have different explanations – the peas exhibit vigorous star formation and are smaller. Infrared observations that can penetrate the thick dust clouds in our green bean galaxies revealed a big surprise: the black holes appeared to be up to 50 times less active than expected from the bright glow of the oxygen emission. The best explanation we have is that the black hole has very recently reduced its output significantly, and thus also the amount of ionising X-ray photons. At the same time, we see most of the gas in the galaxy still shining brightly, echoing the earlier higher levels of X-rays bombarding it. Ionisation echoes like that allow us to directly investigate how quickly a quasar can shut down. These processes are expected to last well over 100,000 years, but have never been observed directly. Green beans therefore open a new window to help astronomers study this important phase in the life of a galaxy. S

SOUTHERN HEMISPHERE IN APRIL With Glenn Dawes

00:00 23:00 22:00

CO A

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> 1 April > 15 April > 30 April

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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The constellation of Corvus, the Crow, is high in the evening sky. Its four main stars, all third magnitude, are arranged in a trapezium shape and look nothing like a bird. Two of these stars are white, the other two yellow. Only 15° to the right (east) of Corvus is mag. +1.0 star Spica (Alpha (a) Virginis). Look left (west) to find the challenging constellation of Crater. You need dark skies to see the half dozen 4th- and 5th-magnitude stars that make up the bowl of this goblet.

α

Magnificent Saturn is at opposition in April and visible for most of the night. Although its rings are a dazzling sight in any scope, its brightest moon, mag. +8.4 Titan, also makes a great target. A 2.5-inch scope will show it well. Titan’s orbit appears as a flattened ellipse, making its closest approach while passing Saturn’s polar regions every eight days. These conjunctions happen at a distance of 1 arcminute from the planet. They occur to the south on the 5th and 21st, and to the north on the 13th and 29th.

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STARS AND CONSTELLATIONS

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STAR BRIGHTNESS:

DIFFUSE NEBULOSITY

ASTEROID TRACK

DOUBLE STAR

METEOR RADIANT

VARIABLE STAR

QUASAR

MAG. +3

COMET TRACK

PLANET

MAG. +4 & FAINTER

MAG. 0 & BRIGHTER MAG. +1 MAG. +2

S EA

NASA/ESA/AND THE HUBBLE HERITAGE TEAM (STSCI/AURA)-ESA/HUBBLE COLLABORATION, CHART CONVERSION BY PAUL WOOTTON

α

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skyatnightmagazine.com 2013

SC

δ

Corvus contains the brightest example of two interacting galaxies visible to amateur scopes. From Algorab, follow the constellation to mag. +2.6 star Gienah (Gamma (g) Corvi) and continue for another 3.5° to find NGC 4038 and NGC 4039, the Antennae Galaxies (RA 12h 1.9m, dec. –18° 52’). These merged blobs seem to have a chunk missing from one side, with the northern lobe being more prominent.

CHART KEY

PLANETARY NEBULA

α

11

Mag. +3.0 star Minkar (Epsilon (e) Corvi) is at the top of the trapezium in Corvus at 22:00 EST. Diagonally opposite it is mag. +2.9 star Algorab (Delta (d) Corvi, RA 12h 29.8m, dec. –16° 31’). There’s another star close by: mag. +4.3 Eta (h) Corvi is 0.6° to the northeast. A small telescope reveals that Algorab itself is a double star, with components separated by 24 arcseconds.

GLOBULAR CLUSTER

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DEEP-SKY OBJECTS

OPEN CLUSTER

12

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28

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Neptune. Arriving about 02:30 EST midmonth, this distant gas giant is best seen in the pre-dawn eastern sky. Uranus returns to the morning, rising at around 04:00 EST by the end of April. Mercury is best seen low in the east about one hour before sunrise.

EAST

Jupiter is just to the right of mag. +0.9 star Aldebaran (Alpha (a) Tauri), low in the northwest evening sky towards the end of twilight. Next comes Saturn, rising around sunset and well up in the east by midevening. The morning selection includes

GALAXY

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Winter Triangle

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Procyon

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skyatnightmagazine.com 2013

ADVERTISEMENT FEATURE

CREDIT: NASA, ESA, AND M. LIVIO AND THE HUBBLE 20TH ANNIVERSARY TEAM (STSCI)

astronomy THE GUIDE TO

DARK SKY DESTINATIONS AND WHERE TO STUDY To advertise with us please contact Steve Grigg: [email protected]

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DARK SKY

Destinations

Here’s a great selection of places to stay where you can relax in comfort and enjoy the experience of dark sky observations

LLANERCHINDDA FARM

The Starry Isles of Scilly ñ Dark Sky Heaven at Hell Bay The boutique hotel Hell Bay on the island of Bryher, just 28 miles off the Cornish coast. Stargazersí Island Break: £590 four nightsí Dinner B&B per person including return 

This 3-star guest house and its self -catering cottages look on to the Brecon Beacons that have just been given Dark Sky Status so it’s ideal for observing the night sky. Situated in Cynghordy near Llandovery, we are also the perfect base for exploring and enjoying the beautiful heartland of Wales.

01550 750274 [email protected] www.cambrianway.com

For more information please call us 01720 422947 | www.hellbay.co.uk

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A world apart, but not a world away. . . The Castle ramparts are the perfect location to view the heavens. The clarity of light is simply unrivalled, matched only by the service & facilities of our renowned 4 star Hotel. S.W.England Restaurant winner 2013.

Galloway

Galloway Forest Park

home to the UK’s only Dark Sky Park

S TAR . C ASTLE . H OTEL I S L E S O F S C I L LY St.Mary’s Isles of Scilly TR21 0JA Tel: 01720 422317 / 423342 E-Mail: [email protected] www.star-castle.co.uk

YNYSHIR HALL

Imagine a sky full of stars, darkness all around with only nature as your companion. Bortle class 2, the Milky Way, good food, fabulous wildlife, amazing events and a great welcome. Imagine no more, it's here! Grab your binoculars and visit the UK's only Dark Sky Park. Scotland's Heavenly Wonder.

Located in the Dyfi Biosphere, gaze at the twinkling stars in the inky darkness of the night.

01654 781209 [email protected] www.ynyshirhall.co.uk

THE PHEASANT INN

For more information visit our website or call us on 01671 402420 www.forestry.gov.uk/darkskygalloway

TABOR HILL FARM, EXMOOR

Located deep in the heart of darkest Northumberland close to the Sir Patrick Moore Observatory, Kielder Water and Forest Park with heavenly dark skies.

This AA 4-star farmhouse bed and breakfast is set in 200 acres within the Exmoor national park. There are uninterrupted views of the sky and all rooms are en suite.

01434 240 382 [email protected] www.thepheasantinn.com

01598 740 528 www.taborhillfarm.co.uk

GALLOWAY ASTRONOMY CENTRE

ROMNEY BAY HOUSE HOTEL

This B&B accommodation is near the UK’s first dark sky park. There are a range of telescopes, and courses for beginners. Children and pets welcome. From only £26 pppn.

01988 500594 [email protected] www.gallowayastro.com

This hotel is on the seashore with flawless panoramic views over the English Channel. No light pollution makes for a five star experience.

01797 364747 www.romneybayhousehotel.co.uk

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WHERE TO STUDY THE

You can learn more about the Universe by taking an astronomy course. There’s a wide variety on offer, covering all age groups and levels of experience, to help you take your interest further.

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UNIVERSITY COLLEGE LONDON

PLANET EARTH EDUCATION

The UCL Certificate of Higher Education in Astronomy is taught at the UCL campus in Central London. The two year course of part-time study requires no subject-related A-level. Study is in UCL’s Physics and Astronomy Department, one evening per week from 6 to 9pm. It has a much greater coverage of astronomy than ordinary evening classes and includes regular practical classes at UCL’s superbly equipped Observatory at Mill Hill. This course is ideal for keen amateur astronomers, teachers and everyone interested in learning more about astronomy. The certificate is endorsed by the Royal Astronomical Society.

A popular and long standing provider of astronomy distance learning courses. All courses enjoy an excellent reputation and a certificate is awarded for each completed course. Students have easily accessible, oneto-one contact with their tutors. Five astronomy courses available: - GCSE Astronomy - for a certificate - PEC Nature of the Planets - learning for fun about the solar system - PEC Nature of the Stars - learning for fun about the night sky - PEC Astronomy - to GCSE standard but without the exam - PEC Advanced Astronomy - for the more dedicated student

Details and application form are linked on the web page below

Also available: The Mobile Stars Planetarium – an exciting educational experience for children in schools and for scouting groups.

020 7679 3943 [email protected] www.phys.ucl.ac.uk/part-time/PTAstro/

0161 653 9092 www.planeteartheducation.co.uk

UNIVERSITY OF CENTRAL LANCASHIRE

CARDIFF UNIVERSITY

As one of the world’s leading providers of distance learning astronomy study, UCLan offers a range of part-time courses starting from University Certificates up to Honours Degree level. University Certificates are singlemodule awards designed for people with no prior knowledge of the subject. They can be used towards more advanced awards leading to our BSc (Hons) Astronomy. Visit www.studyastronomy.com for more information. UCLan’s BSc (Hons) and MPhys (Hons) Astrophysics, based at our wellappointed and modern campus in Preston, provide essential training in understanding the physical concepts that govern our Universe. Visit www.uclan.ac.uk/courses for more information.

01772 892400 [email protected] www.studyastronomy.com

Cardiff School of Physics and Astronomy houses one of the UK’s largest communities of astronomers and astrophysicists. Learn Physics and Astrophysics in an internationally renowned, friendly research environment. - A range of 3 year (BSc) and 4 year (MPhys) undergraduate degrees, with a core first year to allow for flexibility between schemes - A BSc programme in “Physics and Astronomy with a Professional Placement” - Final year independent projects, working with real astronomers on real research topics - An on–site astronomical observatory, control rooms and data processing laboratories - Learn transferable skills allowing excellent employment possibilities - Become part of a friendly and thriving capital city and a vibrant student community

02920 876457/874144 | www.astro.cf.ac.uk [email protected]

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

Observing the Sun through an h-alpha filter is an incredible experience… Solarscope manufacture complete h-alpha telescopes available in unobstructed 50mm and 60mm apertures as well as a range of h-alpha lter systems which can convert your existing astronomical telescope into a high quality solar instrument. H-alpha lter systems are available in unobstructed 50mm, 60mm, 70mm and 100mm aperture sizes. The dedicated Solarview (SV) telescope range provides you with everything you need to observe the Sun in h-alpha apart from a mount and clear skies! These solar instruments are manufactured to the highest quality and will give you views of our nearest star which will literally take your breath away. The solar lter system (SF) range consists of a totally unobstructed front mounted etalon with a matching rear mounted blocking lter which ts into your telescopeís eyepiece holder. A custom made adapter plate is used to securely mount the etalon over the front of your telescope. Using laser industry techniques our lter systems are manufactured to the highest optical tolerances.

Prestige hydrogen-alpha solar lters manufactured in the Isle of Man

For information on Solarscope filters Contact: Ken Huggett

07624 435572

[email protected]

www.solarscope.co.uk

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