BBC Sky at Night 2014-03

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LETTER FROM THE EDITOR MARCH 03 WorldMags.net

Welcome

This month’s contributors include...

Now our Sky Guide is even more useful under red light

MAGGIE ADERIN-POCOCK

Look out after dark on any clear night The new Sky at Night at the moment and presenter there’s something introduces unmistakable in the herself in night sky – Jupiter. her ﬁrst monthly column Our planetary to tie in with the TV show. system’s largest ELIZABETH PEARSON world – 2.5 times the STAFF WRITER mass of all the other What can a star’s planets put together – has been shining bright colour tell since January, when it was at opposition. March, us about the however, is a great time to observe Jupiter’s star itself? fascinating detail: it reaches its highest point Elizabeth takes a look in the sky, so its light is least disturbed by our at the evidence in this atmosphere, and it reaches it early in the month’s The guide. evening, so it’s the ideal time to show the GOVERT SCHILLING view to budding young astronomers. Make ASTRONOMY AUTHOR sure you can answer all their tricky questions What does the future and take a picture they’ll remember with our hold for the deﬁnitive guide to observing and imaging professional this King of Planets – it starts on page 32. observatories To have Jupiter, one of the Solar System’s nearing the end of their showpieces, so nicely on view soon after the useful lives? Govert travels to Chile to ﬁnd out. excitement of Comet ISON really raises awareness of the wider Universe for everyone. PAUL SUTHERLAND Professional astronomers are only just SCIENCE WRITER beginning to unravel ISON’s fascinating Paul looks at the results story. Read more about their efforts to of the understand this primordial chunk of rock GRAIL and ice in Will Gater’s feature on page 40. mission You’ll notice a slightly different look to to examine the hidden our Sky Guide, starting on page 47. We’ve structures beneath the Moon’s surface. made it even more red light friendly and SKY AT NIGHT PRESENTER

HOW TO CONTACT US binders, CD cases and back issues Subscriptions, 0844 844 0254 Mon to Fri 8am to 8pm; Sat 9am to 1pm for orders Editorial enquiries 0117 314 7411 9.30am to 5.30pm, Mon to Fri Advertising enquiries 0117 314 8365 email enquiries Subscription [email protected]

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Editorial BBC Sky at Night Magazine, Immediate Media Co

Bristol Ltd, Tower House, Fairfax Street, Bristol, BS1 3BN

increased the size of the charts right through its 15 pages, so it’s even more usable out under dark, open skies. Of course, the skies may still be cloudy, but don’t be disheartened: instead turn to page 70 to ﬁnd out how you can get your astronomy ﬁx online by imaging with a remote telescope situated in one of the world’s darkest spots. Enjoy the issue!

Chris Bramley Editor

PS Next issue goes on sale 20 March.

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

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Find out what The Sky at Night team will be exploring in this month’s episode on page 19

Visit our website for reviews, competitions, astrophotos, observing guides and our forum

All the details of our latest issue, plus news from the magazine and updates to our website

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Follow @skyatnightmag to keep up with the latest space stories and tell us what you think

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04 CONTENTS MARCH

In the magazine ON THE COVER 32

32

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

THE DEFINITIVE GUIDE TO JUPITER

40

70 16 78

47

90 66

56

FEATURES

11 Bulletin 19 What’s on

Stunning new images of space.

32 The deﬁnitive guide to Jupiter THINKSTOCK, LYNETTE COOK/SCIENCE PHOTO LIBRARY, WWW.THESECRETSTUDIO.NET

40 The perils of perihelion Catch up with the scientists who are trying to work out what actually happened to comet ISON.

78 Skills 78 The guide The secrets of star colour.

81 How to 85 Sketching

New Sky at Night presenter NEW Maggie Aderin-Pocock joins us with a new monthly column.

M101, the Pinwheel Galaxy.

66 GRAIL: beneath the surface

87 Scope Doctor Your gear problems solved.

23 Jon Culshaw

89 Reviews

Jon’s off-world travelogue continues.

First Light 90 Borg 89ED f/4.3 astrograph. 94 Celestron Skyris 445C

26 SUBSCRIBE

What’s next for Chile’s aging observatories?

skyatnightmagazine.com 2014

FIRST LIGHT

21 A passion for space

24 Interactive

62 Observing in an uncertain future

How easy is it to take an astro image with a robotic scope? We try our hand at it to ﬁnd out.

98

Build a powertank protector.

All you need to know to observe and image the mighty gas giant as it rides high in the sky.

70 Imaging from afar

THE PERILS OF PERIHELION

REGULARS

06 Eye on the sky

How a pair of orbiters that never landed on the Moon dug up the secrets of its interior.

40

colour imaging camera.

Get your issues at a discount

98 Pentax Astrotracer DSLR

28 Hotshots

102 Books 104 Gear

47 THE SKY IN MARCH Your 15-page guide to the night sky featuring the top sights, an all-sky chart, a WorldMags.net deep-sky tour and more…

camera kit.

106 What I really want to know is… When is a star not a star?

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MAN IN SPACE iPAD APP

Celebrate 50 years of mankind’s adventure in space

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

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

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A light

in the

dark The rhythmic pulses from RS Puppis give rise to an amazing phenomenon: echoes of light HUBBLE SPACE TELESCOPE 17 DECEMBER 2013 Bursting through the centre of its dusty cocoon, the incredibly bright star RS Puppis illuminates the interwoven strands of nebulous material that surround it in this vibrant new image from the Hubble Space Telescope. One of the most luminous of the Cepheid variables, RS Puppis is 10 times more massive than our Sun. The variable star follows a regular pattern, rhythmically brightening and dimming over a six-week period. Although impossible to make out from a single image, astronomers studying a range of images of RS Puppis noticed that changes in the star’s luminosity was causing the surrounding nebula to ﬂicker in brightness. These light ﬂashes, pulses of energy from the star rippling through the nebula, are known as light echoes.

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ACKNOWLEDGMENT: H. BOND (STSCI AND PENNSYLVANIA STATE UNIVERSITY)

NASA/ESA AND THE HUBBLE HERITAGE TEAM (STSCI/AURA)-HUBBLE/EUROPE COLLABORATION/

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EYE ON THE SKY MARCH 09 WorldMags.net

W Depth perception HUBBLE SPACE TELESCOPE, 7 JANUARY 2014 In this groundbreaking image, Hubble reveals the smallest, faintest and most abundant galaxies ever seen in the early Universe. Using galaxy cluster Abell 1689 as a gravitational lens, the space scope exposed 58 ancient galaxies as they would have appeared more than 10 billion years ago.

A downward slope X MARS RECONNAISSANCE ORBITER 10 DECEMBER 2013 The dark markings on this Martian slope, located in a crater on the ﬂoor of the Valles Marineris, are called recurrent slope linea. These dynamic geographical features change with the seasons, appearing to crawl up the slope during warmer months and recede back down again in cooler ones.

W The noble nebula

Blown away X HUBBLE SPACE TELESCOPE 16 DECEMBER 2013 The bright young star at the centre of this Hubble image, V633 Cassiopeiae, is responsible for the cavernous gaps in the thick curtain of cosmic dust that surrounds it. The star has been expelling powerful jets of gas into the surrounding clouds, causing shockwaves. These turbulent spaces, one on the left and one on the right, are known as Herbig-Haro objects.

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KEY PROGRAMME SUPERNOVA REMNANT TEAM; NASA, ESA AND ALLISON LOLL/JEFF HESTER (ARIZONA STATE UNIVERSITY), ESA/HUBBLE & NASA

Observations from the Herschel Space Observatory and the Hubble Space Telescope have been combined to produce this revealing image of the Crab Nebula; Herschel data is shown in red, Hubble data in blue. Using the same data, astronomers found evidence of argon hydride in the nebula. This is the ﬁrst time that any noble gas molecule has been detected in space.

NASA/ESA AND B. SIANA AND A. ALAVI (UNIVERSITY OF CALIFORNIA, RIVERSIDE), NASA/JPL-CALTECH/UNIV. OF ARIZONA, ESA/HERSCHEL/PACS/MESS

HERSCHEL AND HUBBLE 12 DECEMBER 2013

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Image of Ghost Nebula (vdB 141) shot using our new Aspen CG16m CCD camera ©2013 Apogee Imaging Systems Inc. Aspen is a trademark of Apogee Imaging Systems, Inc.

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BULLETIN MARCH 11 WorldMags.net

Bulletin The latest astronomy and space news written by Hazel Muir

PLUS

CUTTING 14 CHRIS LINTOTT 16 LEWIS DARTNELL

EDGE

Our experts examine the hottest new astronomy research papers

Once Rosetta reaches the comet it will drop a lander down to the surface

COMMENT by Chris Lintott

ESA’s ‘sleeping beauty’

ESA–C. CARREAU/ATG MEDIALAB

It’s all systems go for the most ambitious comet mission on record

awakens

ESA’S ROSETTA SPACECRAFT has successfully awoken from its 31-month hibernation. The comet-hunting probe will arrive at 67P/Churyumov-Gerasimenko in August and escort it for more than a year as it swings around the Sun. Rosetta was launched in March 2004. The probe’s path took it too far away from the Sun for its solar panels to fully function, meaning its instruments had to be temporarily powered down in June 2011. But on 20 January, a pre-programmed internal ‘alarm clock’ successfully reawakened the spacecraft in preparation for its rendezvous with 67P/ Churyumov-Gerasimenko later this year. “With Rosetta, we will take comet exploration to a new level,” says Alvaro Giménez, ESA’s director of science and robotic exploration. “This incredible mission continues our history

of ‘firsts’ at comets, building on the technological and scientific achievements of our first deepspace mission, Giotto, which returned the first close-up images of a comet nucleus as it flew past Halley in 1986.” Rosetta will extensively map the comet’s surface for two months, measure its gravity and mass, and analyse its atmosphere of gas and dust. In November, it will drop a lander onto the comet to drill into the ice and relay panoramic views as well as hi-res surface images. The spacecraft will then accompany the comet for a further year. “All other comet missions have been flybys, capturing fleeting moments in the life of these icy treasure chests,” says Matt Taylor, ESA’s Rosetta project scientist. “With Rosetta, we will track the evolution of a comet on a daily basis for over a year.” > See Comment, right

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Waiting for the ﬁrst signal that Rosetta had awoken from its long sleep was a nerve-wracking experience, not helped by the fact that it seems the spacecraft went back to sleep for a few minutes after ﬁrst engaging the wake up routine. The wait isn’t over, with the slow process of checking out Rosetta’s systems and instruments dependent on the meagre power currently being supplied by the spacecraft’s solar panels. All seems well so far, and the excitement over Rosetta’s forthcoming journey must have warmed the hearts of all at ESA. Despite the scientiﬁc success of missions like Herschel and (hopefully) GAIA, it’s seemed recently that the headline grabbing adventures, like landing on Mars, belonged to NASA. As Rosetta rides on its comet around the Sun, for the ﬁrst time in decades we Europeans have not only a scientiﬁc success, but an adventure on our hands. Hang on tight! CHRIS LINTOTT co-presents The Sky at Night

skyatnightmagazine.com 2014

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NEWS IN

BRIEF MOUNTAINS RIPPLE VENUS’S CLOUD TOPS

ESA/VENUS EXPRESS/VMC/A. PICCIALLI ET AL./2014., THINKSTOCK, ESO/S. BRUNIER, UCL/UNIVERSITY OF LONDON OBSERVATORY/ STEVE FOSSEY/IAN HOWARTH/BEN COOKE/GUY POLLACK/MATTHEW WILDE/THOMAS WRIGHT, CORBIS, ALMA (ESO/NAOJ/NRAO)/A. ANGELICH. VISIBLE LIGHT IMAGE: THE NASA/ESA HUBBLE SPACE TELESCOPE. X-RAY IMAGE: THE NASA CHANDRA X-RAY OBSERVATORY

Wave trains have been seen rippling through the high-level clouds that blanket Venus. An analysis of the atmosphere by ESA’s Venus Express spacecraft shows that the waves, which are most active above the lee side of mountains in the planet’s northern hemisphere, probably propagate all the way up from the surface. “We believe that these waves are at least partly associated with atmospheric ﬂow over Ishtar Terra, an upland region which includes the highest mountains on Venus,” says Silvia Tellmann from the University of Cologne in Germany. “The waves may form when a stable air ﬂow passes over the mountains.”

The Sun Top and side (inset) views of our Galaxy showing where the ﬂeeing stars have come from

The Sun

Runaway stars

baffle astronomers

The newly discovered class of hypervelocity stars defy explanation SPACE STATION LIFE EXTENDED President Obama’s administration has approved an extension of US funding for the International Space Station until at least 2024, allowing extra time for research into the health risks of longduration crewed missions and to encourage growth in commercial space transport.

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AROUND 20 SUN-LIKE stars have been spotted barrelling outwards from the Milky Way at speeds of more than a million kilometres an hour – fast enough that they’ll eventually escape from our Galaxy altogether. Astronomers say they’re bafﬂed as to why these ‘hypervelocity’ stars are moving so fast. More than a dozen hypervelocity stars have been discovered in our Galaxy before, all large blue stars that formed near the Galactic centre. Theory suggests they were ‘kicked’ out of the region at high speeds due to the powerful gravity of the supermassive black hole in the Galactic core, and that they’re destined to ﬂy into intergalactic space. But these stars, discovered by Lauren Palladino from Vanderbilt University in Tennessee and colleagues, are neither blue, nor appear to have come from the core of our Galaxy. The new rogue stars appear to have the same composition as normal stars in the Milky Way’s disc, suggesting that’s where they formed. There are no indications that they were born in our Galaxy’s central bulge, the halo that surrounds it or some other exotic place outside the Milky Way.

The astronomers hope to ﬁnd out why the stars have such high speeds. “It’s very hard to kick a star out of the Galaxy,” says Kelly HolleyBockelmann, assistant professor of astronomy at Vanderbilt. “The most commonly accepted mechanism for doing so involves interacting with the supermassive black hole at the Galactic core. That means when you trace the star back to its birthplace, it comes from the centre of our Galaxy. “None of these hypervelocity stars come from the centre, which implies that there is an unexpected new class of hypervelocity star, one with a different ejection mechanism.” Further observations are being made to check the results. Measuring the speed of a star accurately requires observations of its position over decades, and any errors in measurements over such a long time interval can make a star seem to move much faster than it really does. “We did several statistical tests to increase the accuracy of our estimates,” says Palladino. “So we think that, although some of our candidates may be ﬂukes, the majority are real.” www.sdss.org

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BULLETIN MARCH 13 WorldMags.net

Students spot rare supernova The exploding star was one of the nearest in decades BY COMPLETE CHANCE, undergraduate students at University College London (UCL) have helped to discover one of the closest supernovae to Earth in recent decades. On 21 January, they observed the stellar explosion in a galaxy 12 million lightyears away. Astronomer Steve Fossey from UCL was showing the students how to use the CCD camera on one of the university observatory’s 0.35m telescopes. Clouds were gathering, so the students homed in on bright M82, the Cigar Galaxy, in one of the few patches of clear sky.

While adjusting the telescope’s position, Fossey noticed a ‘star’ in the galaxy that he hadn’t seen in previous observations. The team looked at archived images and conﬁrmed that there was indeed a new transient source, then alerted observatories around the globe. Follow-up observations showed it was a Type Ia supernova, thought to be the explosion of a white dwarf star. “One minute we’re eating pizza then ﬁve minutes later we’ve helped to discover a supernova – I couldn’t believe it,” says student Tom Wright. www.ulo.ucl.ac.uk

The bright supernova, ofﬁcially SN 2014J, is one of the closest to have been spotted in recent decades

Dobson revolutionised the design of amateur scopes

ASTRONOMERS MOURN JOHN DOBSON AMERICAN ASTRONOMY PROMOTER John Dobson passed away on 15 January 2014, aged 98. He developed what’s now known as the Dobsonian telescope, a large yet portable, low-cost Newtonian reﬂector that’s easy to manufacture from readily available components. He also co-founded Sidewalk Astronomers, a public service association whose members set up telescopes in streets and parks to allow the passing public to look at fascinating objects in the night sky. This year’s International Sidewalk Astronomy Night on 8 March will be dedicated to his memory. “Amateur astronomers around the globe can join in and celebrate John’s life and continue to carry the torch that he lit back in 1968 when he co-founded the San Francisco Sidewalk Astronomers,” the organisation said a statement on its website. www.sidewalkastronomers.us

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NEWS IN

BRIEF DUST CHOKES YOUNG SUPERNOVA Astronomers using ALMA have spotted copious dust in a very young supernova remnant. This backs theories that supernovae are a major source of silicate and graphite grains in dusty galaxies. The team, led by Remy Indebetouw from the National Radio Astronomy Observatory in Virginia, found the dust in the debris of a star seen exploding in 1987. “This is the ﬁrst time we’ve been able to really image where the dust has formed,” he says.

HUBBLE UNCOVERS ‘MISSING’ GALAXIES NASA’s Hubble Space Telescope has conﬁrmed the existence of a long-suspected but elusive population of extremely faint galaxies in the distant Universe. They probably produced the bulk of new stars in the young cosmos. “There’s always been a concern that we’ve only found the brightest of the distant galaxies,” says study leader Brian Siana from the University of California, Riverside. The Hubble observations suggest the faint galaxies were around 100 times as abundant as their more massive cousins detected to date.

skyatnightmagazine.com 2014

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14

CUTTING Our experts examine the hottest new research

EDGE

Was Einstein wrong? A tantalising idea about how galaxies group together could change our view of the Universe

just 400,000 or so years old. For a Universe with a given amount of stuff in it the effects of the expansion are relatively easy to calculate. This combination gives us a statistical prediction of how the galaxy population must behave, but can’t tell us where to ﬁnd any individual system. As a result, the key to using galaxies to trace cosmic evolution is to have a lot of them, and here this new paper is groundbreaking. Thanks to the Sloan Digital Sky Survey, the team have precisely 690,826 galaxies to play with. Put another way, they are able to say their survey covers more than 200 billion cubic lightyears – that’s a big enough volume to make looking for changes over time possible. This lets us address the biggest mystery in all of modern astronomy: the nature of ‘dark energy’, the mysterious acceleration of the Universe’s expansion. One of the critical clues as to the nature of this mysterious force is understanding whether it changes over time. Perhaps sadly, the new results are consistent

“One of the critical clues as to the nature of dark energy is understanding whether it changes over time”

ALAMY, NASA/ESA AND J. LOTZ/M. MOUNTAIN/A. KOEKEMOER AND THE HFF TEAM (STSCI)

The strength of the research lies in its sample – spanning 200 billion cubic lightyears – but it’s hard to tell at this point whether it’s enough to challenge Einstein’s theories

A

new paper looking at how galaxies cluster demonstrates just how sophisticated modern observational cosmology has become. Given the scale of the work involved, it’s not too surprising that the team, led by Lado Samushia of the University of Portsmouth, look longingly at the most intriguing result in the data, which they say ‘mildly favours’ models in which gravity is weaker than expected from general relativity. Anything that contradicts Einstein is big news, so how seriously should we take this claim? We need to start with the relationship between the distribution of galaxies we observe in our local neighbourhood and the history of the Universe as a whole. Galaxies ﬁnd themselves where they are primarily as a result of two things – the distribution of tiny ﬂuctuations in density established in the Universe’s ﬁrst few seconds and the expansion of the Universe since then. The initial ﬂuctuations can be observed in the cosmic microwave background, the relic light that reaches us from a time when the Universe was skyatnightmagazine.com 2014

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.

with a model in which dark energy’s strength remains constant, contradicting prior work from the same team that had suggested that, at ‘2-sigma’ statistical certainty, there was evidence from galaxy clustering that something was changing. This now seems unlikely. The deﬁnition of a ‘2-sigma’ result is one which has roughly a ﬁve per cent chance of being due to nothing more exciting than random variations. As this paper’s results – ﬁnding galaxies to be more spread out than would be expected with full strength gravity – are shown to disagree with general relativity to only a 2-sigma level, some scepticism is required. Experience says that 2-sigma results tend to disappear when further data is acquired, and I’d bet a decent bottle of wine that’s what will happen here. It’s certainly worth keeping an eye on, though.

CHRIS LINTOTT was reading… The Clustering of Galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey by Lado Samushia et al Read it online at http://arxiv.org/abs/1312.4899

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BULLETIN MARCH 15 WorldMags.net

A colour image using data from Dawn shows melted rock and more A NEW COLOUR-coded image of Vesta, the giant asteroid observed by NASA’s Dawn spacecraft during 2011 and 2012, has revealed extraordinary features of its landscapes and geological structures invisible to the naked eye. True-colour images of Vesta portray an almost uniformly grey lump pitted by craters. But scientists have given the asteroid a makeover by assigning different colours to various wavelengths of reﬂected light. These highlight areas where rock once melted due to impacts, for instance, and foreign material the impacts delivered. “No artist could paint something like that – only nature can do this,” says team member Martin Hoffman from the Max Planck Institute for Solar System Research in Germany. www.nasa.gov/dawn

It may look like a nebula, but this image actually shows how material ﬂows from a crater on Vesta called Aelia

WATER VAPOUR FOUND AROUND CERES OBSERVATIONS BY ESA’S Herschel Space Observatory have revealed water vapour around the dwarf planet Ceres, the largest body in the asteroid belt. It’s the ﬁrst time that water has been detected in this region and, says study leader Michael Küppers from ESA’s European Space Astronomy Centre in Spain, proves that Ceres has an icy surface and an atmosphere. Küppers’s team estimates that the dwarf planet ejects around 6kg of water vapour per second from two localised regions with surface water ice. The most likely explanation for this is sublimation, where ice turns directly to gas, but cryovolcanism could also play a role. http://sci.esa.int/herschel

More detailed information on the dwarf planet’s water vapour should emerge when Dawn arrives in early 2015

Looking back March 1985

It wasn’t until the 1700s that we realised that the comet was periodic

On 10 March 1985, The Sky at Night broadcast discussed Halley’s Comet, due to reach the inner Solar System the following February. The comet zooms around the Sun with an orbital period of just over 75 years. Although it was recorded in ancient times, it wasn’t until 1705 that English astronomer Edmond Halley correctly concluded that it periodically returns. When a comet passes close to the Sun, it heats up and releases

gases, brightening and sometimes sporting a tail. Unfortunately, the 1986 appearance of Halley’s Comet turned out to be unspectacular. But for the ﬁrst time, astronomers could use space telescopes to observe it ‘awakening’ in sunlight, conﬁrming that it’s made of dusty grains as well as volatile ices such as water and carbon dioxide. Halley’s Comet will return again in 2061. For most people, seeing it is a once in a lifetime opportunity.

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NEWS IN

BRIEF ALIEN EARTHS ARE OFTEN GASSY Earth-mass planets are not necessarily like Earth, astronomers have found after studying an alien world called KOI-314c. The planet orbits a star 200 lightyears away that was monitored by NASA’s Kepler spacecraft. KOI-314c is the lightest planet to have both its mass and physical size measured. Despite having the same mass as Earth, it is 1.6 times wider, meaning it must have a very thick atmosphere. “This proves there’s no clear dividing line between rocky worlds like Earth and ﬂufﬁer planets like water worlds or gas giants,” says David Kipping from the Harvard-Smithsonian Center for Astrophysics in Massachusetts.

COSMIC LENS SPOTTED IN GAMMA RAYS Astronomers have made their ﬁrst gamma-ray measurements of a gravitational lens – where the gravity of a massive object bends and ampliﬁes light from a source directly behind it – using NASA’s Fermi space telescope. Fermi detected several bright gamma-ray ﬂares from a lensed energetic galaxy called a blazar. “Over the course of a day, one of these ﬂares can brighten the blazar by 10 times in gamma rays,” says Stefan Larsson from Stockholm University in Sweden.

skyatnightmagazine.com 2014

C. PULLIAM & D. AGUILAR (CFA), NASA, NASA/JPL-CALTECH/UCLAMPS/DLR/IDA, ESA/ATG MEDIALAB, ESA/MAX-PLANCK-INSTITUTE FOR SOLAR SYSTEM RESEARCH

Vesta’s hidden geology revealed

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16 BULLETIN MARCH

CUTTING Our experts examine the hottest new research

EDGE

Life in a lukewarm Universe Could the early Universe have been warm enough to allow life to form right after the Big Bang?

bathed in the all-encompassing radiant light of the cosmic background – the warm glow of the Universe itself. This, Loeb argues, means that our Universe would have provided habitable environments almost as soon as it formed and life could have emerged far, far earlier than anyone has previously reckoned. But things aren’t quite that simple. While the temperature of the 15-million-year-old Universe may be appropriate for life, you also need a few other things. For one, heavy elements: the material to make rocky planets and watery oceans out of in the ﬁrst place – silicon, iron, aluminium, oxygen and so on. The Big Bang disgorged only the simplest atoms, hydrogen and helium, and so the infant Universe was too chemically sterile for life. It is nuclear fusion in the cores of stars that forges these vital elements. So the critical thing is, when is the earliest time that stars could feasibly have formed in the Universe and made available the basic chemical construction kit for life? Fifteen million years is a short timescale

“Early life would have had only the briefest window of opportunity before the Universe chilled around it” If Loeb is correct, a planet would not have neeeded to be in the habitable zone to sustain liquid oceans of water – the warmth of background radiation would have been sufﬁcient

THINKSTOCK

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hen discussing the possibility of life on worlds beyond Earth, one of the key concepts is that of the habitable zone. This is the range of orbits around a star where a planet would possess a surface environment suitable for liquid water: not too close to be boiling hot, nor too remote to be freezing cold. Our search for exoplanets that could harbour life focuses on planets within this climatic sweet spot. Abraham Loeb, an astrophysicist at Harvard University, Massachusetts, has pointed out a more exotic possibility. Today, the afterglow radiation of the Big Bang has been redshifted all the way into microwaves and the effective temperature of the Universe is a mere 2.7º C above absolute zero (which is –273ºC). But go back to when the Universe was only 15 million years old and the ambient temperature of the cosmos would have been a lukewarm 0-30°C. This means that rather than needing to bask at just the right distance from a radiant star, a planet could lie practically anywhere and still sustain oceans as it skyatnightmagazine.com 2014

LEWIS DARTNELL is an astrobiology research fellow at the University of Leicester. His new book The Knowledge will be published in April.

for gas clouds to collapse into the ﬁrst generation of stars, synthesise and release heavy elements into the cosmos, and then for next-generation stars and planets, and possibly life, to form. Loeb argues, however, that clumpiness in the young Universe could have led to regions dense enough for star-forming halos to produce massive stars. Such high-density clumps would not have been common in the early Universe, but they are not ruled out by current cosmological models. The ﬁnal problem is that the duration of this habitable epoch was only a few million years. If life did get started back then it certainly didn’t have the chance to evolutionarily progress beyond simple singlecelled organisms. Early life would have had only the briefest window of opportunity before the Universe chilled around it and all planets too far from their star froze, snufﬁng out any precocious ecosystems.

LEWIS DARTNELL was reading… The habitable epoch of the early Universe by Abraham Loeb Read it online at http://arxiv.org/abs/1312.0613v1

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What’s on

Our pick of the best events from around the UK

Going Dark The Science Museum, London, 5-9 March, 2.30pm (selected dates) and 7.30pm

PICK

OF THE MONTH

Exploring the Liverpool Telescope William Hulme’s Grammar School, Manchester, 10 March, 7pm This month, West Didsbury Astronomical Society will host Prof Mike Bode, director of the Astrophysics Research Institute at Liverpool John Moores University. He will discuss the university’s 2m robotic Liverpool Telescope, which is situated on the Canary Island of La Palma. The event is free to members and visitors are welcome. For more details, visit the society’s website at www.wdas2.com.

Observing Evening Torquay Boys’ Grammar School, Torquay, 6 March, 7.30pm Join Torbay Astronomical Society for an evening of visual treats. For their March observing evening, society members will be focusing on the giant planet Jupiter, the Crab and Orion Nebulae, and open cluster M67. The event is free to members, and there’s a £2 admission fee for non-members. Visit www.torbayastro.org.uk for more information.

Going Dark has been described as a “pulse-quickening poem” by critics

THE SCIENCE MUSEUM, ALAMY, NASA/ESA/J. HESTER/A. LOLL (ASU), THINKSTOCK X 3

After a series of sell-out performances at London’s Young Vic, Going Dark, a creative look at the cosmos from theatre company Sound&Fury, is heading to the Science Museum. This one-man show follows Max, a passionate astronomer and narrator at his local planetarium, as he attempts to answer some of the most profound questions in the Universe. Then a major event disrupts the equilibrium in the protagonist’s life and

the universal questions he’s so used to proposing suddenly become more relevant than ever before. Expertly blending an educational and informative look at the cosmos with real life situations and experiences, this multimedia performance is suitable for the whole family and a must-see for astronomy and theatre enthusiasts alike. Tickets can be booked online and cost £20 per adult, £15 for concessions. www.sciencemuseum.org.uk

BEHIND THE SCENES

Stardust, Meteorites and the Early Solar System The British Geological Survey, Keyworth, 6 March, 8pm Hear Jamie Gilmour, professor of planetary science at the University of Manchester, discuss the nature of stardust, meteorites and the formation of the early Solar System at Nottingham Astronomical Society this month. The event is free to all. Visit www.nottinghamastro.org.uk for further details.

THE SKY AT NIGHT IN MARCH Four, 9 March, 10pm*

THE SOUNDS OF SPACE This month, the team explore the sounds of the Universe. Lucie Green reports on how studying sound waves on the Sun can help us to build a new picture of its interior, Chris Linott explores how sound waves are recorded in the cosmic microwave background, and Maggie Aderin-Pocock listens in on the ‘ticks’ of distant pulsars. We’ve watched the night sky for centuries; *Check www.radiotimes.com as times listening to it could prove just as enlightening may vary

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

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Our Night Sky WorldMags.net Taught by Professor Edward M. Murphy UNIVERSITY OF VIRGINIA

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A PASSION FOR SPACE MARCH 21 WorldMags.net

A PASSION FOR

with Maggie Aderin-Pocock

The Sky at Night’s new co-presenter tells us what inspired her to forge a career in space science

BBC

M

y ﬁrst awareness of the night sky was via the Moon. Even as a toddler I was fascinated by our lunar companion and growing up in London it was one of the few things that could be seen through the glare of streetlights. As I grew up I heard about the Moon landings, and then everything seemed possible. At this stage the idea of getting into space was mainly to meet my favourite TV characters, the Clangers. As I grew older the desire to get into space grew through reading science-ﬁction stories and watching programmes such as Star Trek. Viewing the stars did not seem to be enough, but visiting them was highly desirable. My opinion changed when I started to watch The Sky at Night. My parents had noticed my interest in things ‘out there’, so I got special permission to stay up late and watch it. Suddenly there was more to see than just the Moon. With Patrick’s guidance I was able to spot constellations and planets. I was hearing about missions investigating the Solar System and telescopes helping us to understand the Universe. I was hooked and wanted to know more. I started searching out books on astronomy and began thinking about the next step, my own telescope. But

the telescope, but for me it was a means of getting closer to the stars. After the telescope class we would go to an observatory on Hampstead Heath. The telescope was developing well and I thought about building a tracking system for it. I did this as my ﬁrst year project while studying for my physics degree at Imperial College London. I got the telescope bug so badly that I started to specialise in optics, going on use it in my PhD. Finally I got to work on one of the largest telescopes in the world, Gemini South, an 8m triumph of engineering that my team and I built a high-resolution spectrograph for. It seemed amazing and a dream come true after working on my own small system. This project led on to a career in space, working on telescope instruments, including one for the James Webb Space Telescope. Now, being a member of The Sky at Night team feels like coming full circle. In the past few years much of my time has been spent sharing the wonders of the night sky with a range of audiences; co-presenting this programme feels like the ultimate way of doing this. S

Maggie at NASA Space Center Houston for her 2011 BBC2 documentary Do We Really Need the Moon?

this was going to be a tall order. I would scan magazines looking at the systems available, but sadly beyond my teenage budget. I decided to start somewhere and bought a cheap plastic refractor, but was very disappointed with the results.

An engineer is born I thought that my observations would be limited until I was a bit older when I discovered a telescope-making class at a local school. I was stunned: was it possible to make a quality telescope? I joined the class and found that I was the youngest there at 15, but I was with like-minded people. I started to make a 6-inch Cassegrain system – quite challenging for a novice. Some of my companions at the class were there for the technical challenge of making

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Maggie Aderin-Pocock is a space scientist and co-presenter of The Sky at Night skyatnightmagazine.com 2014

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EXOPLANET EXCURSIONS MARCH 23 WorldMags.net

JON CULSHAW’S

MAIN ILLUSTRATION BY MARK GARLICK, THINKSTOCK, PHOTO: EMMA SAMMS

Jon swaps paradise for thick ice as he continues his tour of the Kepler 62 system PULSAR PLANETS AND lava worlds are spellbinding to look upon, but these dangerous environments mean that only the briefest visits are possible. Kepler 62e – where we stopped last month – is the utter opposite. It’s a paradise world where the most natural reaction is a desire to stay for many decades. For a while, then, we shall. These habitable conditions call for a spot of exoplanet astronomy. There’s room in the Cruiser Globe’s maintenance store for my 12-inch reﬂector, so we can observe our home star as it appears from here as a fragile, ﬂickering point of light. Observing the Sun from a faraway alien place brings profound pangs of emotion – fondness, pride, even vulnerability. It’s a reassuring connection to home. Thoughts of Earthly sunrises are front of mind as Kepler 62e’s sky looks ready for a sunrise of its own. We’ll imminently have the chance for the most amazing compare and contrast as the red star

rises spectacularly above the horizon, lightening the alien sky through a sequence of shades like a 1970s car colour chart. Black to dark Roman bronze, tawny to copper metallic and Sebring red, then ﬁnally a spectacular tangerinetinged Arizona gold. Kepler 62’s light once again illuminates the perpetual ocean views of this water planet, stretching beneath cloud formations I’ve never seen the likes of. Interweaving cumulonimbus horsetails resemble long, stretched cloud bands on Jupiter as they lace across the sky like rigging on an old pirate ship. What kind of intriguing atmospheric movement creates such patterns? The rose-illuminated waters show signs of effervescence, as if they’re carbonated. Could this be a sign of life existing deep down in these Keplerian oceans? I reverse the Cruiser Globe back over the terminator to observe the rise of Kepler 62e once more, then reluctantly, I steer away from this paradise planet. But in no more than 10 minutes I’m faced with the looming presence of neighbouring super-Earth Kepler 62f. A quick pit stop seems a grand idea.

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On the outer edge of this system’s Goldilocks zone, 62f is habitable but harsh. In this much cooler region, the oceans on 62f are frozen, making our surface view one of endless jagged, angular columns of ice, clustered up against one another like a haphazard dog-tooth check of shattered glass. It’s reminiscent of Jupiter’s moon Europa, but with sound; this vista of interlocked ice lets out a series of cracks, creaks and rumblings, like a tape recording of the pops and crackles of a log ﬁre played at very slow speed. I’m suddenly struck by the strong similarities of this star’s habitable zone to our own Solar System: Earth with greatest inhabitability followed by more distant Mars with its harsher environment, but habitable with adaptations. That pattern is echoed in Kepler 62’s Goldilocks zone, and I wonder whether this increases the odds for life taking hold where it can throughout the Universe. Who knows when we’ll encounter some alien cousins face to face?

Jon Culshaw is a comedian, impressionist and guest on The Sky at Night

24

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Interactive EMAILS s LETTERS s TWEETS s FACEBOOK 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 2014 is a month-by-month guide to the year and you’ll be able to ﬁnd all the best sights with Patrick Moore’s The Night Sky. Stargazing with Binoculars by Robin Scagell and David Frydman contains equipment and observing guides, and you’ll be viewing planets, galaxies and more with Storm Dunlop’s Practical Astronomy.

MESSAGE OF THE MONTH A homebrewed dew solution Many thanks to Martin Lewis for his article about dew problems in the February issue of BBC Sky at Night Magazine. I have found myself getting very frustrated with dew forming on my eyepieces and ﬁnderscope. In the ﬁeld, I often ﬁnd the only method I have at hand to deal with it is wiping the lenses with a cloth – a big no-no! The price of commercial dew heaters is prohibitive for me, so I decided to have a go at making my own. With a few resistors, other electrical components and modest electrical know-how, I built the unit pictured right. It is a simple electrical component box with switches, RCA connectors, standard phono leads and heaters made out of 0.5W resistors. For example, the eyepiece heater is composed of eight 12Ω resistors in series, creating 1.5W at 12V, which works well for keeping the dew away. I have a bit of tidying up to do with the tape, as you can see, and I need to add velcro so the heater can be used with different-sized eyepieces. I also plan to add a PWM fan speed controller to connect to the fan in the mirror box of my 10-inch

Another one gets the bug Last year, I ﬁnally decided to have a go at amateur astronomy. With little knowledge of what I wanted to achieve or what I really needed, I scoured the internet to see how big a telescope I could afford (I now know this wasn’t the best approach but some things you have to learn the hard way). There was a guy close to home selling a Sky-Watcher 200PDS with an EQ5 Go-To mount and lots of extras in my price range. I arranged to meet him and view the equipment to check that it was all working and in good order. Armed with my new large telescope and mount I was ready to view the heavens, totally ignoring the fact that I had no true idea of how to set up this mechanical miracle I now had in my possession. Like a stereotypical man I totally ignored the manuals and instructions that came with my new toy. With bits of telescope and mount strewn across the front room, I had set myself a real challenge. I had of course forgotten a couple of things in doing all this in one morning – ﬁrst, informing my skyatnightmagazine.com 2014

Þ Rhys’s low-tech, low-cost dew solution proves how much you can achieve with a bit of ingenuity Dobsonian. All this cost around £20 – plus a few bits I already had lying around – a fraction of the cost of commercial units. Rhys Hardwick, Barry

Great work there Rhys, a clever solution to a common problem faced by so many astronomers. – Ed

wife that I was going to purchase a telescope; second, that I had a three-month-old daughter who thought anything was edible and everything belonged to her. Yep, you can imagine the explaining that had to go on that afternoon. It’s been 10 months since I bought my ﬁrst telescope and a lot has changed. My little girl is now walking, my wife is talking to me again and I no longer work my night job as it interfered too much with the chance of getting out with my telescope and viewing the heavens. Needless to say I am a man with a new addiction. I don’t have as much money in my bank account as I used to have, but some things are worth spending your hard-earned cash on. Teudor Acton-Page, Falmouth

An inspiring story Teudor, once you catch the astronomy bug it’s a difﬁcult one to shift! – Ed

Sketching supernovae I was lucky enough to observe the supernova in M82 and decided to have a go at sketching it at the

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LETTERS MARCH 25 WorldMags.net eyepiece. It was discovered by accident the day before (22 January) by students at University College London. It’s 12 million lightyears away; quite exciting to see an event that happened so many millions of years ago.

The big

Nicholas Cox, Swadlincote

debate Have your say at http://twitter.com/ skyatnightmag @skyatnightmag asked: Who is your astronomy hero and why? @sextantnav Nevil Maskelyne, creator of the Nautical Almanac: trusty guide to celestial navigators and mapmakers since 1767. @Blobchaser Giovanni Cassini – engineer, astronomer and all-round clever clogs! @stuperfect Carl Sagan is my astronomy hero: Pale Blue Dot. Enough said. @astroforfun The legend that still is #SirPatrickMoore kept me inspired to do what I do now. @ProfBrianCox does exactly the same. @Softspoken_One Galileo – he made so many discoveries at a time when it was dangerous to do so.

Well spotted Nicholas, it seems January was the month for supernova discoveries with another candidate identiﬁed in M99 just a few days after the M82 ﬁnd. – Ed

What a good idea I’m a great fan of the magazine and thought that it was a good step when you started putting a printable version of the Deep-sky tour on the coverdisc. Now that the magazine has the Binocular tour, would it be a good idea to put a copy of this on the disc as well? Stephen Sampson, Taunton

We agree Stephen. From next month onwards, a printable version of the Binocular tour will be included on the coverdisc. – Ed

Astro imaging on the road This is a photo of the Milky Way that I took from near Picton on New Zealand’s South Island while on holiday. The image is focused on Sagittarius and the Galactic centre. M6, M7 and M8 are all visible as small smudges, forming a right-angle triangle either side of the Galactic centre, which is located in the central dark area. I didn’t have a tripod with me, so I wedged my camera against the campervan for a 19-second exposure. I was using a Canon EOS 500D DSLR at f/3.5 and ISO 3200. Chris Pointer, Tamworth

The southern hemisphere certainly has a wealth of top-class observing sites, great effort there Chris. – Ed

BBC Sky at Night Magazine is published by Immediate Media Company Bristol Limited under licence from BBC Worldwide, who help fund new BBC programmes. EDITORIAL Editor Chris Bramley Art Editor Steve Marsh Production Editor Kev Lochun Online Editor Kieron Allen Staff Writer Elizabeth Pearson Reviews Editor Paul Money CONTRIBUTORS Paul Abel, Piers Bizony, Adam Crute, Maggie Aderin-Pocock, Jon Culshaw, Lewis Dartnell, Glenn Dawes, Mark Garlick, Will Gater, Carol Lakomiak, Pete Lawrence, Martin Lewis, Chris Lintott, Katia Moskvitch, Hazel Muir, Mark Parrish, Mark Payne-Gill, Steve Richards, Steve Sayers, Govert Schilling, Paul Sutherland, Stephen Tonkin 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 Paul Thornton Ad Co-ordinator Emily Thorne Ad Designers Cee Pike, Andrew Hobson Reprographics Tony Hunt, Chris Sutch LICENSING Head of Licensing and Syndication Joanna Marshall MARKETING Head of Circulation Rob Brock Head of Marketing Jacky Perales-Morris Marketing Executive Chris Day Head of Press and PR Carolyn Wray (0117 314 8812) PUBLISHING Publisher Jemima Ransome Managing Director Andy Marshall MANAGEMENT Chairman Stephen Alexander Deputy Chairman Peter Phippen CEO Tom Bureau BBC WORLDWIDE, UK PUBLISHING Director of UK Publishing Nicholas Brett Head of UK Publishing Chris Kerwin Head of Editorial, UK Publishing Jenny Potter UK Publishing Coordinator Eva Abramik [email protected] www.bbcworldwide.com/uk--anz/ukpublishing.aspx EDITORIAL ADVISORY BOARD Deborah Cohen, Andrew Cohen, Michael Ewing, Julian Hector, John Lynch, Bill Lyons, Jonathan Renouf

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@emmajaynepryer Chris Hadﬁeld. #astrohero as well as all his contribution to science and engaging the public, he is just such a cool gent!

© Immediate Media Company Bristol Limited 2014 ISSN 1745-9869

All rights reserved. No part of BBC 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 re-sold, 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.

Þ Even without a tripod, Chris managed to capture this great shot of Sagittarius and the Galactic centre

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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WorldMags.net The perfect addition to your stargazing, BBC Sky at Night Magazine is your practical guide to astronomy, helping you to discover the night skies, understand the Universe around us and learn exciting techniques for using your telescope.

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28

Hotshots

This month’s pick of your very best astrophotos

PHOTO OF THE

MONTH

S Comet C/2012 S1 ISON LAWRENCE DUNN, SOUTHAMPTON, 19 NOVEMBER 2013 Lawrence says: “ISON was only around 5º above the horizon when I started imaging at 5.30am and had only climbed a few more degrees by the time dawn came. There was also a near-full Moon to contend with, but at least there were no clouds! This was my ﬁrst attempt at comet astro imaging; I don’t think it will be my last as it brings with it some unique challenges, especially on the processing side, which is one of the areas I need to improve on. It was great fun though!” Equipment: Atik 460EX mono CCD camera, Takahashi FSQ-106 refractor, Astro-Physics AP 900 GTO mount. BBC Sky at Night Magazine says: “From the detail in the comet’s mottled tail to the

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variable colours in its nucleus, this is one of the best images of C/2012 S1 ISON we have seen. Very impressive indeed.” About Lawrence: “My interest in astro imaging started in October 2010. I was playing with some photographic kit and needed a distant test target, so I stepped outside intending to aim at a streetlamp. Bang in front of me was a full Moon. I then spotted a bright ‘star’, which I centred in my camera screen. My jaw dropped open as I realised the star was Jupiter, complete with some banding and moons. I ended up with some terrible shots of the planet, but I didn’t care.”

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COMET

SPECIAL

HOTSHOTS MARCH 29 WorldMags.net

W Comet C/2012 S1 ISON SPENCER WALKER HERTFORDSHIRE 30 OCTOBER 2013 Spencer says: “This is my ﬁrst image of ISON, taken from my back garden.” Equipment: Modiﬁed Canon EOS 1100D DSLR camera, Sky-Watcher NEQ6 mount.

T Comet C/2013 R1 Lovejoy JAMES COARD COUNTY DOWN 4 DECEMBER 2013 James says: “I initially overlooked Comet Lovejoy due to the hype over ISON. When I did image it, I was amazed by how beautiful it was.” Equipment: Canon EOS 5D Mk III DSLR camera, 3-inch ED refractor.

S Comet C/2012 S1 ISON DAVE WALKER MANCHESTER, 10 NOVEMBER 2013 Dave says: “This was my ﬁrst and last shot of Comet ISON over Manchester, just before dawn. Impossibly faint through the high cloud, I couldn’t see it with the naked eye or through binoculars.” Equipment: Canon EOS 600D DSLR camera, Tamron 18-270mm lens, Vixen Polarie mount.

W Comet C/2012 S1 ISON and an iridium flare MIKE DUVIAU PRESTON, 4 NOVEMBER 2013 Mike says: “This image of ISON and an iridium ﬂare was the last image I took in a six-hour session on the ﬁrst good clear night for about three weeks. This is one of those once in a lifetime images and a shot in a million.” Equipment: Atik 383L+ mono CCD camera, APM 80/470 apo refractor, Sky-Watcher NEQ6 mount.

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30 HOTSHOTS MARCH

Comet C/2012 S1 ISON X SIMON WILSON BAKEWELL 15 NOVEMBER 2013 Simon says: “I was pleased to capture the beautiful green colour of the coma set against a nice star ﬁeld, with a few faint fuzzies for good measure.” Equipment: Atik 460EX CCD camera, Takahashi FSQ85 refractor, SkyWatcher NEQ6 mount.

T Comet C/2013 R1 Lovejoy DAN CROWSON MISSOURI 27 DECEMBER 2013 Dan says: “I ﬁgured that Comet Lovejoy would have cleared the trees at the Danville Conservation Area by 6am, but not so much. I pressed on and took three 60-second exposures.” Equipment: Canon Rebel T2i DSLR camera, Canon EF 50mm lens.

S Comet C/2012 S1 ISON JOHN CHUMACK, OHIO, 13 NOVEMBER 2013 John says: “I had to climb onto the roof of the observatory with all my portable gear just to get above the trees to see ISON, 15 minutes before dawn!” Equipment: Canon Rebel XSi DSLR camera, 300mm telephoto lens.

ENTER TO WIN A PRIZE! We’ve teamed up with the Widescreen Centre to offer the winner of next month’s best Hotshots image a fantastic prize. The winner will receive an Orion StarShoot Solar System Colour Imager IV camera, designed for capturing sharp shots of the Moon and planets.

WORTH

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WWWWIDESCREEN CENTRECOUKs

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

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THE DEFINITIVE GUIDE TO

Jupiter A treat to observe and image, the King of Planets is unmistakably high in the early evening sky this month

T

his month, our early evening skies will be graced by a brilliant visitor. The bright beacon of Jupiter looks to the naked eye like a resplendent creamhued bauble, dominating the stars of Gemini. The planet came to opposition in

January, but Jupiter’s sheer size means it’s still big and bright throughout March. Jupiter has something for everyone, regardless of whether you’re a seasoned imager armed with a light bucket, or a new stargazer out with your telescope for the ﬁrst time. With the planet high in the

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evening sky this month, visible as soon as darkness descends, now is a great time to begin your own exploration of this alien world. Starting on the facing page, we’ll explain how you can observe the King of Planets and its extended family. From page 36, we’ll tell you how to image them.

GUIDE TO JUPITER MARCH 33 WorldMags.net

OBSERVING JUPITER

Paul Abel explains what you can expect to see when you set your sights on Jupiter and its moons

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upiter currently resides in the constellation of Gemini, the Twins, and will remain there for the next few months. If you look eastwards after dark, you will ﬁnd the yellowish brilliance of Jupiter quite unmistakable. At UK latitudes, the planet will climb high into the evening sky, making it much less susceptible to the blurring effects of bad seeing. Perhaps the most striking thing about Jupiter is just how alien it is. There’s no solid surface on which to stand and gaze out across the Solar System. Jupiter is a gas giant: when we look at it through a telescope all we are seeing is the top of a very tumultuous and rather extensive atmosphere. If we could venture down through the planet, we’d have a fearsome journey. At ﬁrst it would be easy going as we drifted down through a cloud deck of ammoniaice crystals, and later, ammonium hydrosulphide. But in the lowest cloud deck (composed of water), the winds really pick up, with speeds of 100 metres per second. As we continue to fall, the

Jupiter blazes bright in the constellation of Gemini all month

pressures and temperatures become extreme, to the point that hydrogen and helium are squashed into a very odd substance called ‘metallic hydrogen and helium’. This churning metallic ocean gives Jupiter a substantial magnetic ﬁeld

– if you could see it in our skies it would be about the size of the full Moon. A telescopic view reveals Jupiter to be crossed by dark belts and brighter zones. The zones are composed of ice crystals higher up in the stratosphere. >

ADVANTAGES OF APERTURE BINOCULARS

SMALL OR MEDIUM SCOPE

LARGE SCOPE

A pair of binoculars will reveal the planet and its four largest Moons. Night after night you will be able to observe the moons, tiny star-like points, change position as they orbit Jupiter. You’ll also be able to catch the planet moving against the background stars of Gemini.

In a small scope, Jupiter is transformed into a yellow disc that looks appreciably ﬂattened. You’ll see a bright Equatorial Zone separating the main equatorial belts. With a medium scope, try looking for bright structures in the larger South Equatorial Belt just following the Great Red Spot; a light-blue ﬁlter will help.

Myriad ﬁne, slowly changing details will be apparent. You can study the small storms and clouds within the main belts and monitor subtle colour changes in the zones. Keep an eye out for Oval BA, a small version of the Great Red Spot, also located in the South Tropical Zone.

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THINKSTOCK X 2, NASA/JPL X 5, PETE LAWRENCE, PAUL ABEL X 3

Paul’s sketches reveal how the equipment you use can affect your view of Jupiter

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> Darker features tend to be lower down in the warmer depths. These belts and zones are governed by powerful jet streams, keeping them in place. A 3-inch scope will reveal the two main equatorial belts and the polar shading. A 6-inch scope will show the temperate belts and zones, along with the brownish hues of the largest belts.

Upping the aperture It’s in 8-inch and larger telescopes that the view is really spectacular. You’ll ﬁnd a number of more subtle belts and zones are revealed – on a good night the details can be overwhelming! White

ovals appear in the South Tropical Zone, swirling structures in the equatorial belts, and festoons (a darker cloud that links two neighbouring belts) streak across the Equatorial Zone. Colour ﬁlters can enhance many of these features by increasing their contrast. Try using a blue ﬁlter to bring out details in the belts, or a red ﬁlter to help sharpen up the zones. A yellow ﬁlter generally sharpens most things on the disc – it’s a good all round ﬁlter for Jupiter. The most famous artefact of Jovian meteorology is the Great Red Spot, a vast hurricane three times the size of Earth that has been raging in the planet’s South

Tropical Zone for hundreds of years. The spot varies in colour and intensity and sometimes fades; at the moment it has a strong orange colour and should be visible in a 4-inch scope. Larger telescopes will reveal subtle structure inside the spot on a good night. Try using a light-blue ﬁlter to help bring out detail. One important thing to remember is that you shouldn’t expect to see these ﬁne details instantly. For good results, spend time – maybe as much as 15 minutes – looking at the planet and taking it in. Use a magniﬁcation suitable for the seeing conditions – around 180x is enough to bring out the ﬁne details on

Jupiter’s atmosphere is rich in complex features, the most famous of which is the Great Red Spot

North Polar Region

North Temperate Zone North Temperate Belt North Tropical Zone

North Equatorial Belt

Equatorial Zone

South Equatorial Belt

Great Red Spot

South Tropical Zone

South Temperate Belt

South Temperate Zone

South Polar Region

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GUIDE TO JUPITER MARCH 35 WorldMags.net The Galilean moons were once thought to be dead worlds; now we know better

Europa

Io Callisto

to be cold, dead worlds. We now know that they’re some of the most fascinating bodies in the Solar System, alive with geology, and sculpted by gravity and cataclysmic impacts. In a small scope, the Galilean moons Keep an eye on the moons appear as bright starand you’ll see them like points, but if you dancing around the planet look at them in an 8-inch instrument, they look like tiny discs. These moons cast shadows into space, and very often they (and their Jupiter has four large satellites: Io, Europa, Ganymede and Callisto. They’re also called respective shadows) will pass in front of Jupiter, an event called a transit. Transits the Galilean moons, as it was Galileo who are great to watch: Ganymede’s shadow discovered them, using a telescope less powerful than the average pair of binoculars. can be seen in a 2-inch scope under good condtions, and certainly a 3-inch aperture Before the Voyager spacecraft visited the is enough to show the shadows of the others. system, the moons of Jupiter were thought an average night. If you want to make a drawing, remember that you need to ﬁnish it in under 12 minutes, otherwise Jupiter’s rapid rotation will have moved the features on. Spend six minutes drawing the main belts, then add the ﬁnal details in the remaining time.

Onto the entourage

Sometimes more than one of these moons makes a transit at the same time; it’s remarkable just how much quicker Io’s shadow crosses Jupiter’s clouds compared to that of outermost Callisto. See if you can spot a transiting moon – to check when these events occur, see our transit diagram on page 53 or use the planetary observing and imaging software WinJUPOS. Jupiter is a planet that never disappoints: it’s constantly changing and no two views are ever quite the same. It’s a world that you can return to again and again. ABOUT THE WRITER Dr Paul Abel is an astronomer based at the University of Leicester. He’s a keen visual observer with a particular interest in sketching.

THREE OBSERVING PROJECTS Begin your quest to explore Jupiter with this trio of observing missions WITNESS A MOON TRANSIT

SEE A FULL DISC ROTATION

PROBE THE GREAT RED SPOT

There’s a particularly interesting transit of Io, the innermost Galilean moon, on 9 March. At about 20:40 UT, Io will be in transit, but you will see two shadows on the disc. The shadow near Jupiter’s following limb (the one that brings features into view) is Io’s; the one near the preceding limb is that of Ganymede, which transited earlier in the day.

Jupiter is a quick spinner, completing an entire rotation in just 9 hours 55 minutes. You can see this for yourself during the ﬁrst week of March. If you start observing by 18:00 UT (or earlier), and you’re prepared to stay out until the planet sets, you’ll have the opportunity to see the whole surface of the planet in a single session.

The best time to see the Great Red Spot is when it’s on the centre of the disc. If you have a small scope, see if you can detect any colour. If you have a larger telescope, try looking for the red spot hollow – this is a bright region that separates the Great Red Spot and the South Equatorial Belt.

Moon

Shadow of moon

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THINKSTOCK, NASA/JPL/DLR, REV. RONALD ROYER/SCIENCE PHOTO LIBRARY, STEVE MARSH X 2, NASA/JPL/SPACE SCIENCE INSTITUTE

Ganymede

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IMAGING JUPITER Pete Lawrence reveals the secrets to getting a clear shot of the mighty planet Good seeing is critical to getting a good image, whatever setup you use

easiest ways to capture this on camera is to centre the planet in a telescope, accurately focus and point the camera down the eyepiece. This technique, known as afocal imaging, can capture Jupiter’s disc, its four bright Galilean moons and even detail in Jupiter’s atmosphere. This detail typically includes the two main belts, and the Great Red Spot if it happens to be on the Earthfacing side of the planet.

Catching good seeing

NASA/JPL, PETE LAWRENCE X 5

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upiter is a spectacular planet to image because it’s big, bright and full of dynamic detail. Earth’s turbulent atmosphere does get in the way though, and this can present problems. A quick look at Jupiter through a telescope eyepiece shows the shimmers and distortions the atmosphere causes. This makes ﬁne detail difﬁcult to discern. These ‘seeing’ effects can vary dramatically from one night to the next, but the fact remains that the best views of any of the main planets and the Moon are generally to be had when they are at their highest point in the sky when due south. The reason for this can be explained by thinking of Earth’s atmosphere as a shell surrounding our planet. Directly above you, you’re looking through the shell at its normal thickness. Look close to the horizon and the apparent thickness is increased – at this point, an astronomical object’s light is reduced and it appears

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redder, because the blue wavelengths of its light are scattered. Seeing-related turbulence also increases. A small telescope can reveal good detail on Jupiter’s large disc, and one of the

An afocal shot is great for taking a snapshot of Jupiter, but the technique does have limitations. A smartphone, point-and-shoot or DSLR camera can only capture Jupiter as the atmosphere delivers it. You could get lucky and snap the planet in a rare moment of good seeing, but typically the result is an image that appears blurred and indistinct. What’s more, pressing the shutter button at the exact moment to capture good seeing is something that, even if you do manage it once, is hard to repeat. An alternative method is to take lots of still shots in rapid succession – the faster the better. This increases the probability that you’ll catch some of the good seeing on offer. The faster the frame rate, the more good quality stills you’ll catch. High frame rate planetary cameras have the sensitive, low-noise chip to take the short enough exposures for frame A high object is viewed through a smaller section of atmosphere so the chance of turbulence is reduced

Object less distorted when viewed directly above

Object is distorted when close to the horizon

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GUIDE TO JUPITER MARCH 37 WorldMags.net

IMAGING METHODS AFOCAL IMAGING

Afocal imaging is quick and simple to do. All you need to capture your image is a telescope set up to deliver a sharp image when viewed through the eyepiece. If you wear glasses, keep them on when achieving focus. A driven equatorial mount is highly recommended to make life easy, but even without one, with a bit of careful timing

you can still achieve a result. lens – but don’t let them Cameras that allow you to touch otherwise you may set ISO sensitivity and scratch one of the exposure time give you surfaces. Try using better control. Try a low-power setting a mid-toeyepiece at ﬁrst, high ISO to start and then with. If you have increase the the option, set magniﬁcation the lens to use a as necessary. low f/number to A remote let in more light shutter release and ﬁnally set the is recommended, exposure time to but if you don’t 0.5 seconds. The have one use your actual time needed will camera’s delay timer depend on your setup, so to take the shot. This AFOCAL RESULT review the image and if too means the picture will bright, lower the exposure time; if be taken a few seconds too dark, increase it or up the ISO. after you press the shutter button, You’ll need to hold the camera so that removing any motion caused by applying its front lens is quite close to the eyepiece pressure to the button.

PLANETARY CAMERA IMAGING

There are many different types of planetary camera currently available, but the basic differences come down to maximum frame rate and whether they take colour or mono images. The mono option requires you to image through RGB ﬁlters and combine them using software to get a full-colour result. A ﬁlter wheel will make life easier but increases the cost of your setup. Choosing a camera without an in-built infrared

rates of 30, 60 or 120-plus frames per second. Even so, noise is still likely to be an issue for single frames. The solution to this is to pull out the good frames and combine them. These can then be aligned (‘registered’) to one another and averaged (‘stacked’) together using free software such as RegiStax. The stacking stage reduces the effects of random noise and improves the quality of the ﬁnal picture. Any telescope with a suitable 1.25-inch ﬁtting can use a high frame rate planetary camera. A driven

blocker is recommended, as this the peak saturation level. Keep would prevent useful infrared it around 80-90 per cent light from swamping what and you should be ﬁne. is a normally infraredThe number of sensitive chip. Some frames you need to RGB imaging sets capture depends have ultraviolet and on the image infrared-blockers scale, but for a built in by default. relatively small Not having one image 500 permanently frames should built in allows be ﬁne. For you to use larger images, speciality infrared anywhere up to pass ﬁlters, which several thousand only let through frames per capture infrared wavelengths. are recommended. PLANETARY CAMERA The capture process Because Jupiter rotates RESULT requires you to get the planet rapidly, there’s a time limit on the chip of the camera, of around two minutes for a full accurately focus and set the sensitivity colour-set capture, but this can be of the camera so that the image does not extended using WinJUPOS’s de-rotation saturate. Most camera control software shows techniques. Visit http://bit.ly/WinJUPOS

equatorial mount makes life much easier, although computerised altaz mounts can also be used.

Getting a closer look Larger image scales, when Jupiter takes up more of the picture, can be achieved by using optical ampliﬁers such as Barlow or Powermate lenses. Inserted between the camera and the telescope, these effectively increase the telescope’s focal length as seen by the camera. The longer the effective focal length, the larger Jupiter will appear

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on the camera’s chip. But don’t overdo it: as a rule of thumb keep your telescope’s focal ratio – that’s its focal length divided by aperture size using the same units – to between f/15 and f/40. Only approach the higher values if the seeing is excellent. For example, a 4-inch telescope with a 1,000mm focal length has a focal ratio of f/10 (1,000 divided 100). A 2.5x Powermate lens multiplies this f/number directly and delivers a focal ratio of f/25. Increasing the effective focal length causes the image that’s delivered to appear > skyatnightmagazine.com 2014

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38 GUIDE TO JUPITER MARCH

PETE LAWRENCE X 6

USING REGISTAX Download the latest version at www.astronomie.be/registax

STEP 1

STEP 2

STEP 3

Click ‘Select’ and pick the movie ﬁle you want to process. The movie will open and present you with the ﬁrst frame. Use the slider at the bottom of the window to step through the movie frames. Stop at a frame that looks particularly sharp. This will become the reference frame that RegiStax will compare all the others to, so take your time here and choose the best you can ﬁnd.

Click ‘Set Alignpoints’. RegiStax will attempt to locate the highest-contrast features in the image and mark them as references points. It will monitor how these features look in all the subsequent frames. You can deﬁne your own alignment points by carrying out Step 1 and clicking on the features you think are the best reference points – in this case, don’t click on Set Alignpoints.

Click ‘Align’. RegiStax analyses all the frames in the movie, assessing their quality and how misaligned they are to the reference frame. The result is the registration graph. The red line in this graph indicates the RegiStax-assessed quality of the frames, while the green line shows how far off alignment they are. The frames are internally sorted in quality order with the best on the left.

STEP 4

STEP 5

STEP 6

Use the frame slider at the bottom of the window to move the vertical bar in the graph. The bar determines the quality threshold of the ﬁnal process. Basically, the bar should be moved to a point where the red quality line indicates the minimum quality threshold you’re happy to accept, typically 80-90 per cent. Any frames to the right of the bar will be rejected and not used in the ﬁnal process.

Clicking on ‘Limit’ conﬁrms your threshold choice. Once done, click ‘Stack’. This instructs RegiStax to work through all the frames that made it through the quality threshold, aligning them to one another and then averaging the image content between frames. The end result is normally a smooth, noise-free image. Save the result using one of the lossless ﬁle formats, for example PNG or FITS.

Repeat Steps 1-5 for all movie ﬁles. Click ‘Select’ and open a result ﬁle from Step 5. This will open in the wavelet sharpening screen. Select the Gaussian option. Moving the sliders to the right sharpens a certain level of detail in the image. Click the preview button to see what is affected; a small tweak on the early sliders is normally enough. Save to a new ﬁle name when done.

> dimmer. Large telescopes with naturally long focal lengths are able to maintain image brightness with decent image scales. Larger apertures also beneﬁt from higher resolving power, meaning they can reveal smaller detail than a small aperture instrument. One-shot-colour cameras can record full-colour still sequences of Jupiter in one go, but there are a number of limitations. For Jupiter, capture times should be kept below 120 seconds to avoid motion blur due to the planet’s rapid rotation. Then there’s an atmospheric effect called dispersion, which spreads the light of a

distant object out into a spectrum in a similar way to a prism. The effect gets worse the lower in the sky you go. Also, some telescope designs cannot bring all colours to the same focus at the same time, resulting in colour fringing. Using a monochrome camera and a set of imaging ﬁlters avoids these issues. The advantage here is a set of crisp individual red, green and blue images. These are then combined to create a sharp, full-colour result. The disadvantage is that ﬁltered captures take longer to complete, so planet rotation becomes more of a problem.

A relatively new technique is now available to undo the rotation of a fast rotating planet such as Jupiter. The freeware program WinJUPOS can do this, and using this method it’s now possible to increase your imaging time to many minutes or even tens of minutes. S

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ABOUT THE WRITER Expert imager Pete Lawrence is a regular on The Sky at Night TV show. He also compiles our Sky Guide – where you can ﬁnd more imaging tips.

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WorldMags.net ISON’s twin tails drew admiring glances ahead of the comet’s fateful encounter with the Sun

LYNETTE COOK/SCIENCE PHOTO LIBRARY

The

perils of PERIHELION Will Gater analyses the ﬁnal days of Comet ISON and asks if we are any closer to understanding the behaviour of this unpredictable visitor WorldMags.net

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n December last year the Hubble Space Telescope turned its gaze towards a tiny patch of sky in the hope of seeing an object leaving our Solar System forever. The handful of grainy, monochrome images it returned showed nothing however, save for the streaks of distant stars, blurred by the motion of Hubble as it tried to track the celestial visitor. The comet that had been relentlessly observed, and indeed hyped, for over a year was nowhere to be seen. C/2012 S1 ISON had vanished. If anything of it still existed, even Hubble couldn’t see it now. ISON’s subdued retreat into the darkness was in stark contrast to its behaviour just a few weeks earlier. As it made its closest approach to the Sun in late November, a point known as perihelion, it created a spectacle that few astronomers will ever forget. For Karl Battams, an astrophysicist and sungrazing comet expert from the US Naval Research Laboratory in Washington DC, it was the culmination of months of watching and waiting. Like many astronomers, Battams’s interest in ISON was piqued shortly after its discovery, when it was found that the comet would have a remarkably close encounter with our star. “At that point I thought, ‘That’s going to be a sungrazer and it’s a really, really long way away from us right now, which means that it should be a really bright object when it gets to us,’” Battams recalls. ISON’s discovery far out in the Solar System gave astronomers

ABOUT THE WRITER Will Gater is an astronomy journalist and author who maintained an overnight vigil when ISON was at perihelion. Find him on Twitter: @willgater

around the world time to organise an extensive observing campaign using telescopes both in space and on the ground. “We’ve only ever had advance warning of one other sungrazing comet [C/2011 W3 Lovejoy] and we only had three weeks’ warning,” says Battams. “To suddenly be told, after years of doing this, ‘Hey you’ve got 16 months to prepare for a sungrazing comet’, was unprecedented.”

Lost in the glare As numerous professional telescopes turned to scrutinise ISON, it continued to race ever farther into the inner Solar System. Amateur astronomers too followed the comet’s progress as it brightened, with many astrophotographers capturing stunning images of its growing tail. But ISON was always destined for a brush with the Sun, and in the days leading up to its perihelion passage the brightening comet disappeared into the glow of the morning twilight. As the scientiﬁc world watched on, wondering if ISON would survive the rigours of perihelion, it fell to orbiting solar telescopes such as the Solar & Heliospheric Observatory (SOHO) to act as the eyes of astronomers everywhere. >

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> At ﬁrst the signs were positive. ISON entered the

ESA/NASA/SOHO/GSFC X 4, NASA/ESA/SOHO/SDO AND FRANCIS REDDY, THINKSTOCK

ﬁeld of view of SOHO’s LASCO C3 instrument on the 27 November and began to brighten, as would be expected of a comet getting so close to the scorching solar inferno. “However, part of us was a little bit worried at the rate at which it was brightening,” says Battams. “It was brightening perhaps a little too fast. It was perhaps marginally ahead of the curve that we would want to see with a sungrazer. The fear that was starting to creep into our minds was that maybe the reason it was brightening so much was because it was falling apart.” As morning broke on the 28 November – ISON’s perihelion day – SOHO images showed the comet sporting two sweeping dust tails. “The top one was very thin and bright. It was [made of] big chunks of dust, probably centimetre-sized or maybe larger grains, that fell off the comet and were basically following the same orbit as it,” explains Battams. “The second tail, the wider more diffuse one, was the classic dust tail that we see on comets. It was very ﬁne dust that tries to follow the orbit of the comet but gets pushed out of that track by radiation pressure, by the sunlight hitting it.” It wasn’t just ISON’s beautiful tails that were attracting attention: as it plunged further towards the Sun, the head of the comet had started to noticeably fade in brightness. As ISON crept into the ﬁeld of view of SOHO’s LASCO C2 instrument – which has a slightly narrower and closer view of the solar corona than its counterpart LASCO C3 – it appeared dramatically different to the comet it had been just hours earlier. “There wasn’t even an obvious nucleus,” recalls Battams. “The comet was more like an arrow that tapered to a very ﬁne point. The whole thing was an unusual shape and that really gave us cause for concern when we saw the appearance of it at conjunction, with the brightness

Þ ISON was brightening worringly fast as it came into SOHO’s sights

behaviour that it had been undergoing.” Before long ISON had disappeared behind the mask that LASCO uses to block the blazing disc of the Sun. With the comet’s two wraith-like dust tails lingering in view, whatever ISON had become now faced the climax of its epic journey away from the eyes of SOHO.

The haggard remains

Þ ISON rounds the Sun, its rapid dimming on approach laid bare

Many had written ISON off when, at around 8pm on 28 November, what Battams calls a “fuzzy, dusty streak” appeared from behind the mask of the LASCO C2 camera. Sure enough, something of ISON had survived its sweep past the Sun, and soon it moved into the LASCO C3 images too. “It seemed very tenuous, very diffuse and elongated,” says Battams. “That to me reeked of a comet that has no nucleus and is just a trail of dust. And that’s basically what it was – just a trail of very heavy dust that was still following the orbit.” As it moved away from the Sun in the SOHO images, the remains of ISON appeared to brighten (see ‘A bright rebirth’, below), giving hope that >

A BRIGHT REBIRTH When ISON emerged from perihelion, it initially appeared to brighten. Comet expert Geraint Jones from the Mullard Space Science Laboratory in Surrey thinks there could be a couple of explanations. “I suspect that the primary one was that the comet’s nucleus had already broken up into fragments before perihelion,” says Jones. “What we were seeing was the regrouping of nucleus fragments and dust as their orbital velocities slowed down, forming a fairly coherent cloud of dust near where the nucleus should have been had it survived.” But another effect may have also contributed to the apparent brightening. “The way that the phase angle – the angle between the observer, the comet and the Sun – changed meant that some of the re-brightening could have been due to that changing angle, as sunlight was scattered more efﬁciently towards SOHO and Earth by the dust that had survived perihelion.”

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Þ SOHO’s LASCO C3 instrument caught ISON’s apparent brightening post-perihelion

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Þ Early optimism was short-lived; this sequence of SOHO images shows how ISON faded as it retreated from the Sun

EXPERT REACTIONS DR GERAINT JONES, MULLARD SPACE SCIENCE LABORATORY

PROFESSOR ALAN FITZSIMMONS, QUEEN’S UNIVERSITY BELFAST

DR NATALIE STARKEY, THE OPEN UNIVERSITY

I had high hopes that ISON would survive in one piece, though of course I was very aware that there was a risk it would fragment. Hoping that it would survive wasn’t foolhardy: Comet C/2011 W3 Lovejoy passed even closer to the Sun than ISON did, and it did survive perihelion. Just the fact that ISON broke up is [scientiﬁcally] valuable in itself, even if it is disappointing.

Like everyone else, I felt a sense of disappointment when it became clear from the SOHO images that ISON’s nucleus had effectively disintegrated. Comet ISON’s passage reinforced our picture of how fragile cometary nuclei are, not to mention how unpredictable their behaviour can be. The real science lessons will appear later this year, as astronomers analyse their data and publish their ﬁndings.

By studying comets as they pass through, we get a chance to probe back in time to the beginning of our Solar System, before the planets formed. Comets preserve all the earliest Solar System forming materials, including water and organic material, untouched and unchanged over billions of years. By studying them we can start to answer some of the most basic questions about our existence.

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> the comet would still be visible after perihelion. The reality, though, was that ISON had disintegrated into a cloud of dusty debris, one that would rapidly fade away in the following days. Pinning down exactly when ISON crumbled isn’t easy and will require detailed scientiﬁc analysis. “I think we’ll ﬁnd that somewhere within the [pre-perihelion] LASCO C3 ﬁeld of view was when the whole thing came undone,” says Battams. “That was the time at which the temperature on the surface of the nucleus got so hot that almost everything was evaporating. Not just ices anymore, but every piece of rock that was on the surface. That’s an extraordinarily stressful time for any comet. When you couple that with the gravitational tidal forces that it’s undergoing at that point too, it’s a really bad combination for a comet.” If any vestiges of ISON are still out there, they’ll now drift away from the Sun and, eventually, leave the Solar System. And although ISON didn’t survive its solar sojourn, much has been learnt about it, says Battams, thanks to the work of amateurs and professionals all over the world. “The collaborative aspect of it has been phenomenal,” he says. Maybe, then, in watching a comet break apart we’ve actually learnt something about bringing things together. S

BABAK TAFRESHI/TWAN/SCIENCE PHOTO LIBRARY, NASA/SWIFT/D.BODEWITS/UMCP, NASA/ESA/J.-Y. LI (PLANETARY SCIENCE INSTITUTE) AND THE HUBBLE COMET ISON IMAGING SCIENCE TEAM, DAMIAN PEACH, SOHO (ESA & NASA) X 3

44 ISON MARCH

Though it didn’t survive perihelion, ISON was still a magniﬁcent sight in the night sky beforehand

THE CHANGING FACE OF ISON

1. This picture of Comet ISON was captured by the Swift space telescope in January 2013. ISON was 740 million km from the Sun at this point.

2. By April 2013 ISON had brightened and was beginning to develop a substantial tail, as this Hubble Space Telescope image shows.

3. As ISON edged closer to the Sun, amateurs were able to image its spectacular tail. Damian Peach captured this shot on 15 November 2013.

4. SOHO images captured just hours before perihelion showed the comet’s bright coma and two beautiful dust tails.

5. By the time ISON moved into the ﬁeld of view of SOHO’s LASCO C2 instrument, the comet appeared highly elongated.

6. ISON’s diffuse form after perihelion suggested that the comet had fragmented, leaving a cloud of dust drifting through space.

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THE SKY GUIDE MARCH 47 WorldMags.net

PLUS Stephen Tonkin’s

BINOCULAR TOUR Turn to page 58 for six of this month’s best binocular sights

The Sky Guide

March PETE LAWRENCE

Written by Pete Lawrence

As well as writing The Sky Guide, Pete can be seen on The Sky at Night on BBC Four. On page 60, he offers advice on imaging waxing crescent Moons like the one on this page.

The waxing crescent Moon is particularly well placed in the spring. This most enigmatic of lunar phases is often accompanied by the dim glow of earthshine, which illuminates the Moon’s unlit night side.

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48

Highlights

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

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SATURDAY X Galaxies are back in style this month. As our own Milky Way appears to rotate out of the way, we get to look into deepest depths of space. Regions such as the Realm of Galaxies and the Leo Triplet, pictured right, are currently well placed for telescope viewing.

7

FRIDAY The waxing crescent Moon (42% lit) is located within the V-shaped Hyades open cluster, which represents the face of Taurus.

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TUESDAY It looks as if Jupiter has an extra moon this evening – the planet passes close to the mag. +9.9 star catalogued as TYC1893-1713-1. The four Galilean moons – Io, Europa, Ganymede and Callisto – are all located to the west of the planet until 01:40 UT.

14

FRIDAY Mercury reaches greatest western elongation today, when it will appear separated from the Sun by 28º. At western elongation Mercury is a morning object.

20

PETE LAWRENCE X 6

26

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18

TUESDAY The waning gibbous Moon (95% lit) is just 1º from mag. +1.0 Spica (Alpha (_) Virginis) as it rises around 21:00 UT. Mars is 4º to the upper-left of the Moon. The Galilean moons form a line to the west of Jupiter this evening.

21

THURSDAY X The March equinox occurs at precisely 16:57 UT. This is the time when the centre of the Sun crosses the celestial equator. The Sun’s centre therefore officially moves from the southern celestial hemisphere to the northern celestial hemisphere at this moment. WEDNESDAY The waning crescent Moon (26% lit) passes a fraction south of mag. +3.1 Dabih (Beta (`) Capricorni) this morning – look from about 05:00 UT. Also see if you can spot Dabih’s sixthmagnitude companion, which sits 3 arcminutes to the west of the star.

16

SUNDAY A double shadow transit on Jupiter occurs this evening. Ganymede’s shadow passes onto the Jovian disc around 22:00 UT, closely followed by the shadow of Io approximately 20 minutes later. See page 51.

FRIDAY X The waning gibbous Moon (80% lit) is just 1º to the south of Saturn this morning. For comparison, the apparent diameter of the Moon in the sky is 0.5º. See page 51.

27

THURSDAY The waning crescent Moon (16% lit) is less than 3º to the north of Venus in the dawn twilight. There’s a trio of Galilean moons to the east of Jupiter as the sky darkens – Europa, Ganymede and Callisto. Io is off to the west.

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W SATURDAY Fabulous open cluster Melotte 111 is due south at midnight. This month our Deep-sky tour covers this region – turn to page 56.

THE SKY GUIDE MARCH 49 WorldMags.net

What the team will be observing in March

2

SUNDAY Look out for a thin waxing crescent Moon shortly after sunset, almost due west. Over the next few nights the crescent will become more prominent. Turn to page 60 for tips on how to image it and the earthshine.

5

WEDNESDAY Jupiter’s apparent motion against the background stars changes direction today, the planet initially heads west and then reverses direction to head east.

9

SUNDAY The waxing gibbous Moon will be close to brilliant Jupiter tonight and tomorrow night. T

Pete Lawrence “I’m really looking forward to observing the double shadow transit on Jupiter that occurs on the 16th. If the sky remains nice and clear I might even attempt to create a simple animation of the entire event.” Steve Marsh “For me this month is about one thing, deep-sky observing. I plan to leave the planets behind and try and tackle our Deep-sky Tour on page 56. I can’t promise not to use my Go-To though.” Paul Money “I’ll be looking out for the slim crescent Moon on the evenings of the 1st and 31st, and especially on the 27th, when it lies close to Venus in the morning twilight.”

Need to know

The terms and symbols used in The Sky Guide UNIVERSAL TIME (UT) AND BRITISH SUMMER TIME (BST) Universal Time (UT) is the standard time used by astronomers around the world. On 30 March, the UK switches to British Summer Time (BST).

RA (RIGHT ASCENSION) AND DEC. (DECLINATION) These coordinates are the night sky’s equivalent of longitude and latitude, describing where an object lies on the celestial ‘globe’.

HOW TO TELL WHAT EQUIPMENT YOU’LL NEED NAKED EYE

22

Allow 20 minutes for your eyes to become dark-adapted

SATURDAY X Dazzling Venus reaches greatest western elongation today. The planet currently appears 47º to the west of our star, making it a morning object visible before sunrise.

BINOCULARS 10x50 recommended

PHOTO OPPORTUNITY Use a CCD, planetary camera or standard DSLR

SMALL/MEDIUM SCOPE Reflector/SCT under 6 inches, refractor under 4 inches

30

SUNDAY The clocks go forward one hour at 01:00 UT, marking the start of British Summer Time (BST).

31

LARGE SCOPE

MONDAY There’s an opportunity to spot a thin waxing crescent Moon just after sunset this evening. See page 50.

Reflector/SCT over 6 inches, refractor over 4 inches

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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50

DON’T MISS…

3 top sights

Thin Moon viewing opportunity WHEN: From 15 minutes after sunset on 31 March 31 March Sunset

31 March Sunset + 30 minutes

31 March Sunset + one hour

10º

Moon

Moon

Moon W W

W

W

W

W

You’ve got until an hour after sunset to catch the crescent, but make sure the Sun has truly set before looking

PETE LAWRENCE X 4

SPRING IS A great time to try and view the waxing crescent Moon. The reason for this is that the plane of Earth’s orbit – marked in the sky by the great circle known as the ecliptic – makes a steep angle with the western horizon after sunset at this time of year. As the Moon’s orbit is only inclined to our own by around 5º, our natural satellite can always been found close to the ecliptic. As a result of the steep angle, the altitude of the crescent Moon and the length

!

NEED TO KNOW

An object’s brightness is given by its magnitude. The lower the number, the brighter the object: with the naked eye you can see down to mag. +6.0.

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of time between sunset and moonset is optimised. If you imagine the Moon as a sphere, half of it is always fully illuminated and half always in darkness. When the Moon lines up with the Sun in the sky, normally either above or below it, we get the dark half presented towards us. As the Moon then creeps farther round in its orbit we, slowly but surely, get to see more and more of the illuminated half. An early glimpse of the thin sliver of moonlight that is the post-new Moon crescent can be surprisingly hard. The reason for this is that the area of bright Moon we see is very thin and doesn’t stand out well against the bright background evening

twilight. For the best results a really clear sky and ﬂat western horizon are essential. On 31 March, just 24 hours after new Moon, a 1% lit

crescent will be following the Sun down in the western part of the sky. At sunset, the Moon will be around 12º from the Sun’s disc. Obviously, the greater the separation the easier it is to see the crescent – a gap of 12º makes this a medium-difﬁculty crescent to locate. At sunset on the 31st, make a note of where the Sun goes down below the horizon. The Moon will be heading towards the same spot from above and left of our star. Wait for the Sun to well and truly set before attempting to locate the Moon. It’s really important that you forget the normal image of the Moon’s crescent as a bright target for this to work. The crescent you’re looking for will be dim and easily lost to the background sky. As the twilight deepens, the visibility of the crescent should improve. The viewing window ends approximately one hour after sunset, when the Moon begins to set.

Thin crescents are not particularly bright and easily fade into the sky

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THE SKY GUIDE MARCH 51 WorldMags.net

Jupiter’s double shadow transit WHEN: 16 March, from when the sky gets dark until the early hours of 17 March

JUPITER HAS MANY moons, but only four large enough to be easily seen with small telescopes on a regular basis. This quartet are known as the Galilean moons after their discoverer, Galileo Galilei. Closest to Jupiter is Io, then Europa, Ganymede and ﬁnally Callisto. These are sizeable bodies: Ganymede is the largest moon in the entire Solar System, measuring 5,262km across; Callisto too is considerably larger than our own Moon. As the Galilean moons orbit Jupiter, they can be seen as bright points of light ﬂitting back and forth either side of the planet’s disc. When they pass between the planet and the Sun they can cast vast shadows on Jupiter’s cloud tops below. The shadows will typically appear as dark,

high-contrast spots on the planet’s bright disc. Single shadows transiting across the Jovian disc aren’t that uncommon. To have two shadows on the disc is less frequent and for three to appear at the same time is quite rare. There’s a triple shadow transit coming up in June; this month we will get an excellent view of a double shadow transit. The show begins on 16 March as soon as the sky gets dark enough to ﬁnd Jupiter. At 19:30 UT, Ganymede will be transiting the planet’s disc. It moves off the disc at 20:18 UT and Io begins its transit almost an hour later at 21:07 UT. Ganymede’s shadow moves onto the disc at 22:08 UT, closely followed by Io’s shadow at 22:21 UT. Io moves off the disc at 23:22 UT and

Ganymede’s shadow

Ganymede Io

E Io’s shadow N Both lunar shadows will sit astride Jupiter’s centre line at 23:18 UT on the 16th

the shadows follow suit on the morning of the 17th. Io’s shadow transit ends at 00:37 UT, Ganymede’s at 01:24 UT. Both shadows are more or

less on the centre line of the planet at 23:18 UT, the larger shadow of Ganymede being just to the south of Io’s at this time.

Moon and Saturn conjunction WHEN: Around 02:30 UT on 21 March

Saturn

This close pass serves as good practice for two similar events later in the year

THE MOON AND Saturn have a close encounter this month. On the morning of 21 March, the centre of the waning gibbous Moon (80% lit) will lie around 1º to the south of the mag. +0.6 planet. As the Moon’s apparent diameter is around 0.5º, the distance between the Moon’s northern limb and Saturn is about 45 arcminutes at closest approach. This occurs around 02:30 UT. Although there’s no cosmic signiﬁcance to this event, it’s always interesting to see a bright planet close to the Moon and even more so to be able to compare the appearance of the Moon’s disc to that of the far more distant planet. This is not the only close approach the Moon will make

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to Saturn this year. Another takes place on 31 August, when the edge of the Moon will pass just 15 arcminutes south of the planet in the evening twilight. Occurring in the dead of night, March’s conjunction is relatively easy to view, making it great training for the August event and a much harder one in October. This third occasion is a real treat, when the waxing crescent Moon (3% lit) fully occults Saturn. The disappearance occurs in daylight with the reappearance happening in twilight.

!

NEED TO KNOW

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

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52

The planets PICK OF THE MONTH VENUS

PETE LAWRENCE X 2

BEST TIME IN MARCH: 22 March, 05:30 UT ALTITUDE: 6º LOCATION: Capricornus DIRECTION: Southeast RECOMMENDED EQUIPMENT: 3-inch refractor or larger FEATURES OF INTEREST: Phase, subtle atmospheric shadings VENUS IS CURRENTLY in the morning sky, best seen around 06:00 UT at the start of the month, low in the southeast. It appears to be travelling eastwards starting Venus dims slightly as March progresses, but not enough to affect its visibility in the dawn twilight from Sagittarius, passing through effect. This is a phenomenon that Capricornus and then on into Aquarius by when the planet will be separated from means Venus’s appearance does not the end of March. Seen from the UK, the Sun by 47º. Look at Venus quite match the predicted phase at these constellations are low through a telescope at the start dichotomy (50% illumination). For down, so Venus never really of March and it will appear gains much height above 32 arcseconds wide with a morning appearances, dichotomy occurs approximately seven days later than it the horizon. 36% lit crescent. By the should due to lighting effects caused by The planet is end of the month it the planet’s thick atmosphere. If you dazzlingly bright, will have shrunk to get a chance to view Venus through a though it does gently 22 arcseconds across telescope, estimate its phase to be either dim from mag. –4.5 to and be 53% lit. crescent, half or gibbous over this period mag. –4.2 throughout The planet’s phase and verify the effect for yourself. the month. Even so, it should be 50% on The end of the month brings another remains easily bright 23 March at around 18:00 highlight – look out for a stunning enough to elevate it above the UT. The 50% phase of Venus, conjunction between mag. –4.2 Venus dawn twilight in which it sits. Venus appears as a when the planet appears as a and the waning crescent Moon (16% lit) Greatest western (morning) half circle, doesn’t occur when crescent at the start on the morning of 27 March. of March elongation occurs on 22 March, it should due to the Schröter

How the planets will appear this month The phase, tilt and relative sizes of the planets in March. Each planet is shown with south at the top, to show what it looks like through a telescope VENUS 15 Mar

MARS 15 Mar

JUPITER 15 Mar

SATURN 15 Mar

URANUS 15 Mar

NEPTUNE 15 Mar NOT VISIBLE

MERCURY 1 Mar

MERCURY 15 Mar MERCURY 31 Mar 0”

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10”

20” 30” 40” ARCSECONDS

50”

1’

WorldMags.net MARS BEST TIME IN MARCH:

31 March, 01:00 UT ALTITUDE: 31º LOCATION: Virgo DIRECTION: South Mars is becoming a prominent object, rising in the evening and reaching culmination, due south, in the early morning. It’s currently in Virgo and not too far from mag. +1.0 Spica (Alpha (_) Virginis). At the start of the month, Mars appears as a bright, mag. –0.5 star with a distinct salmon-pink colour. At the end of the month, its brightness increases to mag. –1.0, approaching that of the brightest star in the night sky, mag. – 1.5 Sirius (Alpha (_) Canis Majoris). Telescopically, things are improving too. On 1 March, Mars presents a 94% lit disc, 11 arcseconds across. By the end of the month, it’ll appear virtually fully lit and 14 arcseconds across. A small scope should show the north polar cap and the dark markings on the surface, but do give your eye time to get used to the view. It’s not uncommon to look through the eyepiece and see nothing but a pinkorange blur at ﬁrst. JUPITER BEST TIME IN MARCH:

1 March, 20:20 UT ALTITUDE: 60º LOCATION: Gemini DIRECTION: South Jupiter remains resplendent, although by the 31st the planet no longer culminates in darkness. On the 1st, a telescope will show plenty of detail on its 42-arcsecond disc. By month end, you’ll need to work a bit harder as the disc will have shrunk to 38 arcseconds, although this is still large by planetary standards. Jupiter stays close to mag. +3.0 star Mebsuta (Epsilon (¡) Geminorum) all month. At an

average magnitude of –2.2 throughout March, the planet dominates this part of the sky. The Moon will make a close pass of the planet on the nights of the 9th and 10th.

JUPITER’S MO ONS

March

SATURN BEST TIME IN MARCH:

31 March, 03:00 UT ALTITUDE: 21º LOCATION: Libra DIRECTION: South Saturn is a morning object, culminating as dawn breaks at the start of the month, but it reaches due south comfortably in darkness by month end. A scope will reveal its beautiful ring system, which is now tilted open by an angle of around 23º. Saturn’s disc currently appears 17 arcseconds across, but unlike Jupiter the view appears much more sedate and calm. The odd white spot may be seen from time to time – these are huge storms in Saturn’s atmosphere.

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

WEST

EAST

1 2 3 4 5 6 7 8 9 10 11 12

URANUS BEST TIME IN MARCH:

1 March, 19:30 UT ALTITUDE: 10º LOCATION: Pisces DIRECTION: West Mag. +5.9 Uranus is 11º above the western horizon as the sky gets dark at the start of the month. After this, the evening twilight engulfs the planet.

13 14 15 16 17 18 19 20

MERCURY

21

BEST TIME IN MARCH:

22

14 March, 06:00 UT ALTITUDE: 1º (very low) LOCATION: Capricornus DIRECTION: East-southeast March 2014 isn’t going to go down as one of Mercury’s best UK appearances. It reaches greatest western (morning) elongation on 14 March, but hugs the horizon at sunrise and will be hard to see.

23 24 25 26 27 28 29 30

NOT VISIBLE THIS MONTH 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

31 8

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Europa

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54

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

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HOW TO USE THIS CHART

GLOBULAR CLUSTER

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PLANETARY NEBULA

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

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CONSTELLATION NAME

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56

Deep-Sky Tour Get better acquainted with the delights surrounding the Coma Star Cluster

Tick the box when you’ve seen each one

M64’s high surface brightness makes it an easy spot even in small scopes

3

4

CHART: PETE LAWRENCE, M64: NOAO/AURA/NSF

1

2

MELOTTE 111

This month’s tour is loosely based around open cluster Melotte 111, the Coma Star Cluster, which lies 288 lightyears from Earth. Melotte 111 occupies an area of sky measuring 7º by 5º and forms part of the constellation of Coma Berenices. It sits one-third of the way along a line drawn between mag. +2.1 Denebola (Beta (`) Leonis) and mag. +1.9 Alkaid (Eta (¡) Ursae Majoris) – the latter is the star at end of the Plough’s handle. With the naked eye, you should be able to see a handful of stars close to the threshold of visibility from a reasonably dark site. Binoculars bring out about 40 stars between mag +5.0 and mag. +10.0. SEEN IT

5

NGC 4565

Among the stars of Melotte 111 are mag. +4.8 12 Comae Berenices and mag. +5.3 17 Comae Berenices. Drawing a line from the first to the second and carrying on for the same distance again will take you to our next target, 10th-magnitude edge-on galaxy NGC 4565. A 6-inch scope shows this as a long, thin and faint line of light, orientated southeast-northwest. The galaxy’s core appears brighter and its bulge is quite noticeable. The thinner regions away from the core appear mottled when viewed with an 8-inch scope using averted vision. The mottled regions also help to define the dark dust lane that runs the full length of the galaxy. SEEN IT

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6

NGC 4559

NGC 4559 lies 2º east of mag. +4.4 Gamma (a) Comae Berenices, which itself is just north of Melotte 111. It is a lovely spiral galaxy inclined to our line of sight, and as a result we see it as an object roughly one-third as wide as it is long. The core appears asymmetric in brightness, due partly to a bright spiral arm that ‘extends’ its brightness farther northwest. A number of faint foreground stars in our Galaxy appear in front of the western half of NGC 4559. These can distract your eyes from seeing the naturally dimming outer regions of NGC 4559 adjacent to the core in this direction. SEEN IT

NGC 4725

Return to Gamma Comae Berenices and follow the constellation towards mag. +4.2 Beta (`) Comae Berenices. Just below the halfway point are a pair of stars, the brighter of which is mag. +4.9 31 Comae Berenices. Located 2º south of this star is another spiral galaxy tilted even more open to our line of sight. This is NGC 4725, a concentrated galaxy with spiral arms tightly wound around its core. A small scope shows it as an elongated patch aligned southwest-northeast. The core appears as a slightly brighter concentration in the middle of the main patch. This galaxy rewards larger apertures well, appearing quite bright against the background sky. SEEN IT

M64

We’ll end our mini galaxy-fest on a brighter note with M64, a lovely spiral located one-third of the way along a line joining mag. +4.3 Alpha (_) Comae Berenices to Gamma Comae Berenices. At mag. +8.5 and with a higher surface brightness than the other galaxies in this tour, M64 can be found using a 3-inch scope without too much bother. The galaxy appears elongated with a gradual brightening towards the core. The core itself is offset south, emphasised by the presence of a dark dust lane wrapped around its northern edge; higher magnifications really strengthen this view. This distinctive feature gives the galaxy its informal title of the Black Eye Galaxy. SEEN IT

24 COMAE BERENICES

If you imagine Alpha, Beta and Gamma Comae Berenices as three corners of a slightly distorted square, fifth-magnitude 24 Comae Berenices marks the fourth corner. This is a rather beautiful binary star – sometimes referred to as the ‘spring Albireo’ – the orange-hued primary contrasts markedly with the blue light of the fainter secondary. Once you’ve located the pair, increase the magnification to show them at their best. For comparison, the separation between both components is 20.3 arcseconds, which is slightly larger than the current apparent diameter of Saturn. SEEN IT

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Binocular tour Discover double stars, a galaxy pair and the secret of Polaris, hidden in plain sight

With Stephen Tonkin

Tick the box when you’ve seen each one

1 M81 AND M82

CHARTS AND PICTURES: PETE LAWRENCE

15 x This month’s tour takes us through the 70 north polar region of the sky and starts with the galaxy pair M81 and M82. Imagine a line from mag. +2.4 Phad (Gamma (a) Ursae Majoris) through mag. +2.0 Dubhe (Alpha (_) Ursae Majoris) and extend it for the same distance. The galaxies should be in the same field as the end of this line; M81 is the brighter of the pair. They offer a very useful way to demonstrate averted vision: as you direct your gaze at one, the other appears bigger, brighter and more detailed. SEEN IT

2 KAPPA DRACONIS

ASSOCIATION

10 x Our next stop is a fine little group of stars 50 of different colours. Mag. +3.9 Kappa (g) Draconis is itself is a hot (14,000ºC) B-type star that is 540 times more luminous than the Sun. To the north are a pair of K-type stars, the brighter of which is mag. +4.9 6 Draconis, only 300 times as bright as our star. To the south we have

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a star with a similar luminosity, the longperiod pulsating variable (mag. +4.9 to +5.0) 4 Draconis. This is a cool M-type star whose temperature is a mere 4,000ºC SEEN IT

3 OYY123

10 x OYY123 sits at the end of a 4° chain of 50 stars that extends west from mag. +3.7 Thuban (Alpha (_) Draconis). The components shine at mag. +6.6 and +7.0, and are easy to split even with handheld binoculars, being separated by 68 arcseconds. The ‘OYY’ marks it as being part of Otto Wilhelm von Struve’s catalogue of double stars. Otto was one of 18 children of the famous 19th-century astronomer Friedrich Georg Wilhelm von Struve, one of whose objects is the next stop on our tour. SEEN IT

4 STRUVE 1972

10 x Struve 1972 is much more of a challenge, 50 with the components being of similar brightness (mag. +6.6 and +7.3) but much closer at 31 arcseconds. To find it during spring

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E

¡

S

Aldibah

`

5º

f

W

e

c

evenings, put both mag. +4.3 Zeta (c) Ursae Minoris and mag. +4.2 Epsilon (¡) Ursae Minoris low in the field of view: Struve 1972 is just under 2° above and slightly to the right of the middle of the line joining them. It is a good test of both the observer and the quality of 10x50 binoculars, so if you are having trouble splitting it, mount your binoculars and make sure they are perfectly focused. SEEN IT

5 ENGAGEMENT RING ASTERISM

10 x Many astronomers view mag. +2.0 50 Polaris (Alpha (_) Ursae Minoris) merely as a convenient marker for the north celestial pole, oblivious to the pretty asterism of which it is part. A pair of 10x50 binoculars will reveal a slightly squashed circlet of mostly 8th- and 9th-magnitude stars, nearly 1º wide, which form the ‘ring’. Polaris itself blazes as the ‘diamond’. SEEN IT

6 NGC 6543

15 x Our ﬁnal stop is another pole: NGC 6543 70 marks the position of the north ecliptic pole, the point on the northern half of the celestial sphere that is always the same angular distance from the Sun. To ﬁnd it, imagine a line joining mag. +3.1 Nodus Secundus (Delta (b) Draconis) and mag. +3.2 Aldibah (Zeta (c) Draconis). NGC 6543 is offset from the centre of this line around 1º towards Aldibah. It looks stellar but for two qualities. First, it has an ethereal green tinge to it. Second, unlike the surrounding stars, it ‘blinks’ as you change from direct to averted vision. SEEN IT

THE SKY GUIDE MARCH 59 WorldMags.net

N

STATISTICS

Moonwatch Crater Triesnecker TRIESNECKER IS A relatively small crater located to the south of Mare Vaporum and northeast of Sinus Medii, the small lunar sea that sits at the centre of the Moon’s near side. A telescope will give the best views of the 27km-diameter crater, revealing it to have a slightly polygonal shape. Rather than being a perfect circle, the rim appears to be made up of straighter sections that together seem roughly circular. The rim walls appear terraced inside and lead down to a fairly wide, undulating ﬂoor. A small mountain peak complex at the centre completes the picture. A number of hills can be seen to the north, but the showpiece is a series of complex rilles, or cracks, which occupy an extensive area to the east of the main crater. Known as Rimae Triesnecker, or the Triesnecker Clefts, these are a most interesting and yet strangely perplexing set of features. Under the right lighting conditions, ejecta material from Triesnecker can be seen to cross the rilles, inferring that the crater is younger of the two. The rilles cross one another, so presumably there is an age difference between them too. Unlike other cracks on the Moon’s surface, there’s no obvious mechanism or related nearby features to suggest what has caused the rilles. In contrast, located 133km to the northeast of Triesnecker is 10km-wide crater Hyginus. It too is associated with a rille, Rima Hyginus. In this case the crater is part of the rille itself, the whole system appearing to be made of small pits connected by collapsed material. Rima Hyginus is quite likely volcanic in origin.

If you can follow the cracks close to Triesnecker some also appear inﬂuenced by the crater. Is this just a trick of the view or is there some link between the younger crater and older rilles? Perhaps the formation of the crater extended the rilles that were already there? As you can see, not everything about the Moon is as simple as it might ﬁrst appear! Triesnecker sits on the midpoint of a line joining two

TYPE: Crater SIZE: 27km wide AGE: Estimated to be younger than 1.1 billion years LOCATION: Latitude 4.2°N, longitude 3.6°E BEST TIME TO OBSERVE: First quarter (evening of 8 March) or six days after full Moon (mornings of 22 and 23 March) MINIMUM EQUIPMENT: 2-inch refractor

similar looking craters: Pallas, 166km off to the west, and Agrippa, 205km to the east. Under oblique illumination there is plenty of delicate detail to be seen. The region to the

E

north and west of Triesnecker shows subtle wrinkle ridges in the lava surface. Several small craterlets can also be picked out, such as 4km Triesnecker F to the east of Triesnecker.

“Ejecta material from Triesnecker can be seen to cross the rilles, inferring that the crater is younger of the two” MARE VAPORUM

HYGINUS

RIMA HYGINUS

RIMAE TRIESNECKER

TRIESNECKER TRIESNECKER F

SINUS MEDII

Unlike nearby Hyginus, there is no obvious relationship between crater Triesnecker and its adjacent rille system

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Astrophotography The crescent Moon and earthshine RECOMMENDED EQUIPMENT DSLR, 300mm focal length or longer lens/scope, remote shutter release cable

ALL PICTURES: PETE LAWRENCE

The tricky part is blending the seam between the lunar crescent and the remaining earthshine

THIS MONTH, WE’RE going to look at how you can capture a waxing crescent Moon along with its accompanying earthshine. The spring months are a great time to catch these beautiful crescents – better than any other time of the year. The reason is that the plane of the Earth’s orbit, marked by the ecliptic, makes a steep angle with the western horizon after sunset in the spring. As the Moon never strays far from the ecliptic, the early crescents appear high up after the Sun slips below the horizon. The aspect of the Moon from now through to May is such that the waxing crescents occur at the start of the month. There are actually two new Moons this month, one on the 1st and one on the 30th. These represent the start of the lunar cycle, with waxing crescent phase occurring in the week that follows each one. At the point of new Moon the lunar disc lines up with the Sun, normally appearing slightly above or below it in the sky. For normal observing equipment, skyatnightmagazine.com 2014

this renders the Moon lost to the Sun’s glare. Over the period that follows, the gradual movement of the Moon along its orbit makes it appear to separate from the Sun. As the Moon slowly moves eastwards, increasing its separation from the Sun, we get to see more and more of its illuminated hemisphere. At new Moon we’re looking squarely at the night half of the Moon’s globe. As the angle between the Moon, Earth and the Sun increases, we get to see more of the daylight part of the globe. The Moon passes through its familiar phases starting with the crescent, then ﬁrst quarter and the gibbous phases, before reaching its full phase, when it is opposite the Sun in the sky. The sequence then plays out in reverse, with the Moon passing though gibbous, last quarter and waning crescent before turning new once again, 29.5 days later.

Imagine what it would be like to look back at Earth from the near side of the crescent Moon. From here, our planet would appear big and bright in the lunar sky – Earth is roughly four times the size of the Moon and about four times as reﬂective. The sunlit Earth is easily bright enough to illuminate the lunar surface around you. Heading back to Earth, we can often see this dim illumination on the dark part of the Moon when the lunar phase is a crescent. Known as earthshine, this is sunlight that has reﬂected off the Earth back to the Moon and then reﬂected back to Earth again – quite a journey! When the Moon is a waxing crescent phase and earthshine is easily visible, the situation is known as ‘the old Moon in the young Moon’s arms’. Imaging the earthshine is pretty straightforward – you simply use a longer exposure than you would for the crescent itself. This overexposes the crescent but will bring out detail on the earthshine-lit portion. If you were to capture an image exposed for the crescent and another for the earthshine, you may be tempted to think that they would line up and produce a view similar to that you’d see with the naked eye. However, achieving this can be deceptively difﬁcult. The steps opposite should help you capture these two shots and blend them seamlessly.

KEY TECHNIQUE MIMICKING THE EYE The human eye has an amazing dynamic range. When you look at a thin crescent Moon showing the glow of earthshine on its night side, it’s easy to take for granted just how amazing it is that your eyes can see both the crescent and the earthshine so naturally. A camera will struggle to do this in one go: you’ll need to combine two different exposures. This technique, known as high dynamic range imaging, is an important astrophotographic skill that can really help with tricky targets like this one.

Send your image to: [email protected] WorldMags.net

THE SKY GUIDE MARCH 61 WorldMags.net

STEP-BY-STEP GUIDE

STEP 1 The best type of camera to use for this project is a DSLR. It needs to be attached to a telescope or lens with a focal length of 300mm or longer – this will give you a large enough image scale to see the Moon’s disc with some detail on it. Coupling the camera directly to a scope or lens of around 1,000mm focal length is ideal.

STEP 2 Although not strictly necessary, a driven equatorial mount will help keep lunar detail sharp, especially in the earthshine exposure. Focus the camera as accurately as possible and set an ISO of 200-400 for the crescent shot. The exposure you’ll need will depend on your kit. Take a shot of 0.5 seconds and review the result as a test.

STEP 3 Adjust the exposure so that the crescent comes out bright but without any white in it: check by looking at the image’s histogram on your DSLR. Take several shots then increase the exposure, overexposing the crescent. Take several shots then increase the exposure again. Repeat this cycle until the image looks really overexposed.

STEP 4 Pick the best crescent shot from the ﬁrst set and load it into a layer based graphics program, such as Photoshop or GIMP. Choose an overexposed shot that’s sharp and shows the earthshine, but doesn’t have too much hazy glare from the cresecent. Load it as a separate layer and align the two shots – reduce the opacity of the upper layer to do this.

Tolerance Magic wand

Layer mask button

STEP 5 Make the upper layer opaque again, then click on the crescent using the magic selection tool. The entire crescent should be selected. If not, undo, increase the tool’s tolerance and repeat. Once most of the crescent has been selected, create a layer mask. In Photoshop, copy the selection, hold down the Alt key and click the layer mask button.

STEP 6 Use the eyedropper tool to sample the sky colour in the overexposed image. Create a blank layer between the shots and ﬁll it with this colour. Set the new layer’s blend mode to ‘Lighten’ and merge with the correctly exposed layer. Finish by applying a Gaussian blur to the top layer’s layer mask and apply until the images join naturally.

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1968

TODAY

Þ The disappearance of most of the staff residences at La Silla Observatory in Chile is dramatically evident in its transformation since 1968

OBSERVING in an uncertain

future What do you do when your observatory becomes obsolete? Govert Schilling toured Chile to ﬁnd out

A

n ominous scene greets me at Camp Pelícano, the entrance of the European La Silla Observatory in Chile. Two vultures are sitting on a road sign, as if patiently awaiting the death of a giant animal. Of course, vultures don’t feed on telescopes, but the two raptors remind me of the deteriorative skyatnightmagazine.com 2014

state of the observatory, where many of the domes are empty, while other telescopes are mothballed. I can’t help wondering how this site will look 50 years from now. In the 1980s, La Silla, run by the European Southern Observatory (ESO), was the largest astronomical observatory in the world. Back then the saddle-

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AGING OBSERVATORIES MARCH 63 WorldMags.net problem is the same: the older generation of telescopes no longer competes with the 8-10m giants that now dominate ground-based astronomical research. Last year I drove the 1,650km from San Pedro de Atacama in northern Chile, close to the newly inaugurated ALMA, to the nation’s capital, Santiago. Numerous detours not only took me to some of the most spectacular scenery in the world, but also to the various observatories that were established here back in the 1960s. What I discovered along the way is that although no one knows how to shut down observatories, it’s tough to keep them alive.

Running on empty

Þ They don’t eat metal, but nonetheless vultures await at the entrance of La Silla Observatory

þ These days it’s HARPS’s use of La Silla’s 3.6m scope that keeps the observatory running; inset, HARPS itself

“We now have ﬁve empty domes and three decommissioned telescopes,” says La Silla deputy site manager Juan Fluxa. “A number of instruments have been handed over to other institutions. For instance, ESO’s 1m Schmidt Telescope is now rented and remotely operated by Lick Observatory. We only provide technical support.” Meanwhile, ESO’s Grand Prisme Objectif twin astrograph is in a Santiago museum; the Bochum Telescope will probably go to the city of Valparaíso for educational purposes and the Dutch Telescope has been donated to a private observatory in San Pedro. What is keeping La Silla alive is HARPS, ESO’s High Accuracy Radial Velocity Planet Searcher. Installed in the ESO 3.6m Telescope in 2003 and operated by the University of Geneva, Switzerland, HARPS has been a proliﬁc exoplanet hunter. “It’s really the best in the world,” says team member Nuno Santos of the University of Porto, Portugal. According to Fluxa, a ‘gentlemen’s agreement’ ensures the sole use of the 3.6m telescope by HARPS for at least another seven years. “If HARPS stops, we have a problem,” he says. >

Þ La Silla Observatory’s canteen, as it was in 1980, reveals the hustle and bustle of days gone by

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ESO X 3, GOVERT SCHILLING, ESO/J.LAUNOIS/BLACK STAR, ESO/H.H.HEYER

shaped mountaintop was bustling with activity, and a few hundred astronomers, technicians, night assistants and observatory staff crowded the premises. Today, with only 40 people present during the week, most of the dormitories are empty and the canteen is deserted. The nearby Las Campanas Observatory, operated by the Carnegie Institution for Science, is working on its own survival strategy. Further south, Cerro Tololo Inter-American Observatory (CTIO), managed by the National Optical Astronomy Observatory (NOAO), has run into similar problems. In Arizona, US, NOAO’s Kitt Peak National Observatory faces an uncertain future; the University of California’s Lick Observatory is threatened by funding cuts. Everywhere, the skyatnightmagazine.com 2014

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CHILE’S AGING OBSERVATORIES

LA SILLA

LAS CAMPANAS

CERRO TOLOLO

La Silla was ESO’s ﬁrst astronomical observatory. Work began on establishing a large European observatory somewhere in the southern hemisphere in 1953; Great Britain had been part of the project to begin with but abandoned it in 1961 in favour of a scheme that would result in the AngloAustralian Observatory being built in New South Wales, Australia. The UK joined ESO in 2002. Cinchado, nicknamed La Silla, was the mountain eventually chosen as the site for the observatory in 1964. Construction began in earnest in 1965 and the La Silla Observatory was inaugurated on 25 March 1969. The 3.6m New Technology Telescope (NTT), which began operations in 1989, was a revolutionary test bed for technologies that were later used in ESO’s Very Large Telescope on Cerro Paranal. At present, only the three largest telescopes at La Silla – of which the NTT is one – are continuously operated.

The Las Campanas Observatory supplanted Mount Wilson Observatory in California as the Carnegie Institution for Science’s primary observing facility. It became an astronomical frontrunner with the construction of the twin 6.5m Magellan telescopes. The twin telescopes – one named after the astronomer Walter Baade and the other after the philanthropist Landon Clay – are situated 60m apart on the Cerro Manqui peak. The Baade scope saw ﬁrst light on 15 September 2000 with the Clay scope following in its footsteps almost two years later. Observations began at the site nearly 30 years earlier, with the 1m Henrietta Swope reﬂector in 1971. For the ﬁrst six years, this was the biggest telescope at the site. Its reign came to an end in 1977, with the arrival of the 2.5m Irénée du Pont telescope. Las Campanas will also be home to the 22m equivalent diameter Giant Magellan Telescope, scheduled to be completed in 2019.

The Cerro Tololo Inter-American Observatory (CTIO) is the southern hemisphere counterpart of the Kitt Peak National Observatory in Arizona, US. Cerro Tololo is home to ﬁve working optical telescopes, the biggest of which is the 4m Victor M Blanco Telescope, which was completed in 1974. In 2012, the 570-megapixel Dark Energy Camera was incorporated into the Blanco scope at a cost of $50 million. Cerro Tololo’s sister site, Cerro Pachón, lies 10km to the southeast and is home to a number of other telescopes that are run by international consortiums that the NOAO is part of. This includes the 8.1m Gemini South Telescope and the 4.1m Southern Astrophysical Research Telescope (SOAR). It is also the site upon which the 8.4m Large Synoptic Survey Telescope (LSST) is currently under construction. If everything goes according to plan, the LSST is expected to begin its observations in 2022.

> The situation is similar at Cerro Tololo. Some

of the smaller domes are empty, some instruments are mothballed and the largest telescope on site, the 4m Victor M Blanco Telescope, is now dedicated to one new instrument: the $50 million Dark Energy Camera (DECam), co-funded by the National Science Foundation and the Department of Energy. Among other things, the 570-megapixel camera will study the role of dark energy in the evolution of the Universe by examining 300 million galaxies. According to CTIO telescope scientist Tim Abbott, “DECam has come to the rescue of the Blanco Telescope. Maybe even of the whole observatory.” Like ESO’s La Silla, Cerro Tololo would be unable to maintain the costly observatory infrastructure needed to keep the smaller instruments running without the inﬂux of money from a big project like HARPS or the Dark Energy Survey. Part of the problem is that other mountaintops have been chosen for new instruments, one reason being the lack of available real estate at the existing sites. ESO constructed its Very Large Telescope on Cerro Paranal, a few hundred kilometres north of La Silla, and the 39.2m European Extremely skyatnightmagazine.com 2014

Þ The Blanco Telescope’s DECam imager – blue, left of centre – does the same for Cerro Tololo as HARPS does for La Silla

Large Telescope will be built on the neighbouring Cerro Armazones. The Large Synoptic Survey Telescope Corporation, of which NOAO is a founding member, will build its 8.4m telescope on Cerro Pachón – already home to the 8.1m Gemini South Telescope and the 4.1m Southern Astrophysical Research Telescope (SOAR). But

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AGING OBSERVATORIES MARCH 65 WorldMags.net can an aging observatory be saved by constructing a next-generation telescope at the same site? Miguel Roth certainly believes so. Roth is director of the Las Campanas Observatory, just north of La Silla. In 2000 and 2002, the twin 6.5m Magellan Telescopes saw ﬁrst light here. They’re still productive, and the same is true for the three smaller telescopes at Las Campanas, one of which is operated by Polish astronomers. When Roth drives me up to a neighbouring mountaintop that was ﬂattened by dynamite blasts in March 2012, I understand why he believes in a bright future for the observatory. Around 2019, the newly created plateau will be home to the 22m equivalent diameter Giant Magellan Telescope (GMT), and there’s room for an identical twin. “For a couple of years, GMT will be the biggest telescope in the world,” says Roth.

Which is not to say that small telescopes have become useless in present-day astronomy. On the contrary, says Nicole van der Bliek, director of CTIO. She takes me to the highest point of Cerro Tololo, where you get a great view of the many small domes of various robotic telescope projects that pepper the slopes of the mountain. They’re being used for automated gamma-ray burst followup observations, for helioseismology studies and educational purposes. “We call this our mushroom farm,” she quips. “But these smaller projects are only viable here because of the continuous funding of the Blanco Telescope.”

Þ If La Silla were to close, ESO agreements mean that no trace could be left – not even the foundations

þ But it’s not all doom and gloom – the Giant Magellen Telescope will open in Las Campanas around 2019

The same is true for the telescopes of the midsized Small and Moderate Aperture Research Telescope System (SMARTS) at Cerro Tololo, run by an international consortium of universities. “One of the four domes is now empty,” says van der Bliek. “A second telescope is hardly being used.” Her dream is to ﬁnd a sponsor to enable CTIO to offer these 1m-class telescopes to astronomers in developing countries. “The idea is still pretty vague, but it would be a wonderful opportunity,” she says. “It would be so sad to have to close down this beautiful site.” Not only would it be sad, it would be next to impossible, explains La Silla’s Juan Fluxa. “The steel constructions and concrete foundations of the domes aren’t easy to demolish. In some cases, they reach down tens of metres into the ground. But one of the Chilean government’s conditions for granting the land to ESO was that we return the mountain to its original state if we ever leave. Maybe we need to discuss options for turning the site into a convention centre or a tourist destination. I just can’t imagine someone will blast everything away – it’s very expensive.” When I left La Silla, the vultures had gone. Maybe the venerable observatory will survive one way or the other, and the same might be true for the other astronomical sites in northern Chile. Big telescopes have been described as the scientiﬁc equivalents of cathedrals. One day, they may turn into the astronomical counterparts of the Egyptian pyramids. S ABOUT THE WRITER Govert Schilling is an astronomer from the Netherlands. With Lars Lindberg Christensen he has co-written a book about telescopes in Chile, titled Europe to the Stars.

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IZTOK BONCINA/ESO, DAVID PARKER/SCIENCE PHOTO LIBRARY, NOAO/AURA/NSF, T. ABBOTT & CTIO/NOAO/AURA/NSF, GMTO, ESO/J.DOORNENBAL

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A

little over a year after the GRAIL probes were deliberately crashed into the surface of the Moon, scientists have used the data they collected to produce the most detailed picture of its interior ever. Ebb and Flow, the twin probes that made up the GRAIL (Gravity Recovery and Interior Laboratory) mission, spent nine months in lunar orbit. During this time they measured variations in the Moon’s gravitational ‘pull’, in a bid to learn more about how our natural satellite formed and what its composition is. The spacecraft, each the size of a small washing machine, were able to detect changes in the distance between themselves with extraordinary precision – just a few thousandths of a millimetre – leading to the discovery that the Moon’s gravity ﬁeld is highly uneven. Lunar basins, craters and mountain peaks were all studied in greater detail than ever before. But Ebb and Flow also mapped the large invisible regions that have so much gravitational pull they can inﬂuence spacecraft in lunar orbit. The presence of these regions explains why probes circling the Moon have been seen, seemingly for no reason, to veer off their prescribed course.

BENEATH THE

SURFACE Two probes have mapped the Moon’s gravity in unprecedented detail. Paul Sutherland investigates their ﬁndings

NASA/JPL-CALTECH, NASA/JPL-CALTECH/MIT

On the double Launched in September 2011, the GRAIL probes took more than three months to travel to the Moon and spent another two getting into orbits where they could map lunar gravity in tandem. From March until May 2012, Ebb and Flow carried out their primary mapping mission, ﬂying in near-circular orbits from pole to pole at an altitude of around 55km. The mission entered a second phase in August 2012, when the probes were dropped to an altitude of 23km – so low that the mission team had to keep making adjustments to stop them from being knocked off course and crashing. GRAIL’s readings would vary as the probes ﬂew, sometimes due to obvious surface features, such as ﬂying over a crater in the ground, where the pull weakened, or over a mountain range, where it would increase. But as they circled the Moon, they also acted as a cosmic X-ray machine, scanning beneath the surface. > skyatnightmagazine.com 2014

HOW DID GRAIL WORK? The GRAIL mission involved placing twin probes a short distance apart in the same orbit around the Moon. Flying together over mountains, craters and hidden underground features, they moved slightly towards and away from each other due to the varying gravitational pull. An instrument on board each probe, called the Lunar Gravity Ranging System, was able to make highly precise measurements of the reactive

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changes in their velocities. From this data, mission scientists were able to produce a detailed map of the Moon’s gravitational ﬁeld in extremely high resolution. GRAIL’s lunar studies essentially mirrored the work of another pair of satellites called GRACE (the Gravity Recovery And Climate Experiment) which have been orbiting the Earth since 2002 to map our own planet’s gravitational ﬁeld.

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GRAIL’s synchronised ﬂying formation was the key to its ability to collect data

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NASA/JPL-CALTECH/MIT/GSFC, NASA/JPL-CALTECH/CSM X 3, MARLI MILLER/VISUALS UNLIMITED/ SCIENCE PHOTO LIBRARY, NASA/GSFC/ASU, NASA/GSFC/ARIZONA STATE UNIVERSITY

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> Most of the gravitational anomalies detected by GRAIL were due to the patterns of features on the lunar surface. But a small number of these ﬂuctuations – around two per cent – came from the effect of features beneath it. The results gave scientists an unprecedented insight into the internal structure of the Moon and what it was made of. For example, strong gravitational pulls were found in areas where there was no topographical cause for them. Instead, the forces were produced by large, dense underground regions known as mass concentrations, or mascons for short. Planetary scientists believe that the mascons are the result of impacts from giant asteroids smashing through the Moon’s thin crust. These features give us glimpse about four billion years into the Solar System’s past, when the Late Heavy Bombardment rendered our cosmic backyard something akin to a shooting gallery. The previously hidden mascons clearly stand out on GRAIL’s lunar gravity map as they resemble the bullseye on a dartboard. Scientists think

that the asteroid impacts sent shockwaves through the lunar interior that reverberated within the crust and drew dense material from within the lunar mantle that lies beneath the crust – creating the telltale ringed pattern.

Crust patterns

Þ The mascons appear as concentric ‘bullseyes’ in GRAIL’s gravity map of the Moon

GRAIL data also revealed that the average global crustal thickness is between 34 and 43km, which is about 10-20km thinner than had been thought. This was an important result because it showed that the general density of the highland crust is much lower than had been generally believed and suggests the Moon is made up of much the same material as the Earth, which in turn supports the idea that the Moon formed from material ejected when Earth was struck by a giant body the size of Mars early in the Solar System’s history. Mission scientists also learned that the crust was porous and had been smashed up to a depth of several kilometres, a feature they now believe to be common to all terrestrial planets. As well as mascons, GRAIL discovered several linear patterns in its gravity map where the

Bouguer gravity (mGal)

600 0 –600

UNDERLYING GRAVITY The colourful images of the Moon produced using GRAIL data are examples of Bouguer maps, which show regions of different gravitational pull once the effects of surface features such as mountains and craters have been removed. In the absence of

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topographical inﬂuences, only Bouguer gravity remains, revealing mass anomalies within the Moon. These patterns, highlighted in false colours for clarity, show the locations of such features as mascons and dikes. They also reveal differences in the

thickness of the lunar crust across the Moon and variations in the density of the crust and mantle. Regions of stronger gravity are red, weaker areas blue. The prominent red circular blobs indicate the presence of the mascons produced by giant impacts.

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GRAIL MARCH 69 WorldMags.net gravity ﬁeld’s resolution at the surface to 5-10km, compared with 80-100km previously. “GRAIL has enabled us to see into the crust and derive the change in crustal density and porosity with depth,” he adds. “We are seeing features below the crust that have no manifestation on the surface and are believed to have originated very early in lunar history. “While we continue to study the crust of the Moon we are beginning to look carefully at the GRAIL data for gravity signals from the lunar interior that can provide information about the lunar core, tides and the mantle.” The science team believe the way to build on GRAIL’s success is to send a spacecraft to land on the Moon to study its interior and return lunar samples to Earth. “The next steps in understanding the surface of the Moon should probably come from a lander that returns a sample to Earth,” Smith says. “For the interior, we really need seismic measurements from several points on the lunar surface. Tentative plans are being developed for both ideas while not ignoring the desire to understand the presence of water ice at the lunar poles. There is much to be done!” S

gravitational pull was stronger than in surrounding areas. These identiﬁed the locations of giant features called dikes, which are cracks beneath the lunar surface that became ﬁlled with molten magma and then solidiﬁed. The dikes can be up to 480km long and 40km wide. They show that the Moon’s molten core expanded during the ﬁrst billion years of its history, just as planetary modellers had predicted, and the Moon became as much as 10km greater in diameter.

Þ Dikes exist on Earth – the

top image is from the US; GRAIL found their lunar cousins, in red above

Grasping gravity The lack of tectonic activity on the Moon means that it has changed little over billions of years, making it a relic from the early Solar System. GRAIL’s treasure trove of data, therefore, can help scientists learn about the formation of planets outside our own Earth-Moon system. Space probes have detected mascons beneath impact basins on Mars and Mercury too, and so information about the lunar examples will give researchers some understanding about how they have altered the crusts of other rocky worlds. When astronauts eventually return to the Moon, the GRAIL data will help them calculate how much energy will be needed to scale mountains or crater walls. “The GRAIL mission to measure the gravity ﬁeld of the Moon was a resounding success and exceeded our expectations,” says Dr David E Smith, GRAIL’s deputy principal investigator. “The two prime reasons that led to this success were the very high accuracy of the GRAIL measurements and the very low altitude above the lunar surface from which the measurements were made. Together, they enabled us to derive the gravity ﬁeld of the Moon with unprecedented accuracy and with very high surface resolution.” Smith says the mission has improved scientists’ understanding of lunar gravity by several orders of magnitude. They have now measured the

ABOUT THE WRITER Paul Sutherland is a space journalist, and the author of Where Did Pluto Go?. Each month he reports on the latest space research in What I Really Want to Know on page 106.

THE DEMISE OF GRAIL Before impact

Before impact

After impact

After impact

EBB

FLOW

Þ New craters can be seen at the crash sites of both GRAIL probes after impact On 17 December, 2012, after ﬁring their thrusters a ﬁnal time to use up fuel, Ebb and Flow were both crashed deliberately into a 2.4km-high peak near the lunar north pole. This dramatic ﬁnale to the mission was designed partly to avoid them coming down randomly on a NASA heritage site, such as where the Apollo missions landed, but also to extract further useful

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gravitational data from the descent. The collisions occurred at 6,050km/h, close to crater Goldschmidt. They took place in darkness, but streaks of ejecta plus small new craters formed by the impacts were later imaged by the Lunar Reconnaissance Orbiter. The crash zone was named the Sally K Ride Impact Site after the ﬁrst US woman in space, who died earlier that year.

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Think you can match Kieron’s efforts, or this stunning shot of the Carina Nebula? The Robotic Scope category is just one of seven being contested in 2014’s Astronomy Photographer of the Year competition. For full details on how to sign up, the rules and how to submit your images, visit the competition website. www.rmg.co.uk/astrophoto

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Imaging

afar

from

Kieron Allen wondered how it easy it would be to take an astrophoto with a professional robotic scope. Read on to ﬁnd out how he did Kieron Allen is Sky at Night Magazine’s online editor. He has been working as a science writer since 2011, after completing a postgraduate diploma in journalism.

W

e all dream of a backyard observatory brimming with the latest astronomy kit and, with enough capital, this needn’t be a pipe dream. But one thing money can’t buy is a clear sky and stable atmosphere. Cue the robotic telescope. Situated in some of the best observing sites in the world, these important astronomical tools give everybody the opportunity to have a go at astrophotography without the countless hours spent hunched over CCD instruction manuals and bleak bank statements. And they can deliver spectacular results – the shot of the Carina Nebula on these two pages was taken remotely using the Siding Spring Observatory in Australia. As an imaging novice, I was eager to ﬁnd out how easy it was to use a robotic telescope myself. There are lots to choose from: iTelescope.net, Observing With NASA, Slooh, LightBuckets and the Faulkes Telescope Project are just a few examples. I decided to go with the Bradford Robotic Telescope at the Teide Observatory in Tenerife as the price was reasonable and the scope is run from the UK. Signing up to the Bradford Robotic Telescope programme was an easy, online process. I opted for a standard subscription – at this ﬁrst stage in my astro-imaging adventure, the 10 picture a month limit seemed more than enough. After receiving email veriﬁcation I was ready to capture my ﬁrst astrophoto. Now all I had to do was choose a target. I decided straight away that I wanted to take multiple images of the same object, so I could try out >

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LÁSZLÓ FRANCSICS, THINKSTOCK

ABOUT THE WRITER

72

WorldMags.net > a number of exposures and experiment with the telescope’s camera array. Obviously, I had to pick an object visible from Teide at the time of year I was planning my observations (December 2013). The staff at the Bradford scope gave me another stipulation: my target had to be more than 15º above the horizon to avoid sky-glow and atmospheric disturbance. For these reasons, I settled on M31, the Andromeda Galaxy.

Programming the scope

ALAMY, © UNIVERSITY OF BRADFORD X 6

Þ There are plenty of lists to help you pick a target, or you can specify coordinates yourself

Þ The next step was to pick the instrument I wanted to use; the default one is ticked for you

The Bradford Robotic Telescope was speciﬁcally built for remote imaging

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Finding and selecting M31 on the Bradford Robotic Telescope website was straightforward. With a clear interface, targets are simple to ﬁnd. I discovered it under the sub-heading ‘Well-known galaxy, nebula or cluster’. Now I had to choose what instrument I wanted to image it with. The Bradford Robotic Telescope comprises three optical setups, named Constellation, Cluster and Galaxy. All three, plus a guidescope, are attached to a single equatorial mount ﬁxed onto a 2m pier. Constellation provides the widest ﬁeld of view, around 40º square, and is designed to capture an area of the night sky large enough to encompass entire constellations. Cluster is another wide-ﬁeld setup, designed to capture stellar clusters like the Pleiades; its super sensitive CCD is coupled with a 7-inch f/2.8 lens. The last, Galaxy, is the only optical system to include a telescope. Aiming for distant Messier and NGC objects along with star ﬁelds, planets and close-up shots of the Moon, the driving force behind Galaxy is a 14-inch Schmidt-Cassegrain. For my opening shot I decided to use Cluster, as it has a wider ﬁeld of view than the Galaxy camera. Adapting its settings was, again, straightforward. All three stages were presented on the same webpage and I was essentially guided through the process – perfect for a novice like me. First, I had to select the exposure time. There is a rough guide to the optimum

REMOTE TELESCOPES MARCH 73 WorldMags.net exposure times for different objects on the page. For galaxies this is around 120,000 milliseconds (two minutes). I chose 110,000 milliseconds for my ﬁrst attempt. Next, I had to decide whether or not to add a dark frame to the image. This step is recommended as it usually results in a better quality image by reducing noise. I did this for all of all my images. Finally I had to choose my ﬁlters. I decided to use full-colour RGB for every image. Being so new to astro imaging I didn’t feel comfortable experimenting with different ﬁlters, but there were options for a wide variety, including clear, neutral density, or no ﬁlter at all. After deciding on a name for the image my ﬁrst request was placed in the job queue. In the hope that all my completed images would come through at around the same time, I immediately entered a further three requests. For my second and third images I opted for slightly shorter exposure times of 100,000 and 90,000 milliseconds, keeping the other settings the same. For my ﬁnal shot I decided to switch to the Galaxy setup and zoom in a little closer, using an exposure time of 100,000 seconds. Now I simply had to wait, a few days at most – or so I’d hoped.

Washed out It turns out that even the world’s best astronomy spots can be hit by bad weather. Just a few days after I submitted my image requests, the Bradford Robotic Telescope was put out of action for over a week while storms battered the Canary Islands. I was unable to check my position in the job queue and, although links to weather

Þ Choosing settings for my shot was easy, only requiring that I complete a short form

Þ A simple processing interface allowed me to quickly tweak colours and more

star ﬁeld. But using the simple image reports and live views of the observatory site were available online, it was impossible processing tools available on the Bradford Robotic Telescope website my images were to predict when communication with the instantly transformed. scope would be restored. After processing, the Although we’re used to bad images taken using the weather here in the UK, wide-ﬁeld Cluster when using a robotic camera immediately scope you can’t take revealed the galaxy’s advantage of those elliptical shape, small breaks in faint dust lanes and the clouds – the companion galaxy power is out of your M110 hovering hands and it’s very below. The results frustrating indeed. from the Galaxy But despite the camera were even more setbacks, a few weeks impressive, resolving after ﬁrst requesting M31’s outer arms. them, my images appeared The editing process itself in my inbox. Þ My raw image was was a surprisingly simple At ﬁrst glance the results a bit lacklustre – not an encouraging start affair. After selecting my weren’t that impressive: in image I simply had to click the all of my shots, the ferocious ‘Edit’ button to bring up the processing heart of the Andromeda Galaxy appeared software. This consisted of a handful > as a mere smudge against a dappled

ROBOTIC SCOPES IN EDUCATION Philip Benson, IT technician at Shoeburyness High School in Essex, explains how giving students access to the robotic Faulkes Telescope is helping them engage in real science How did the school get involved with a robotic telescope scheme? Our head of science Mark Smith, went to an event and signed the school up to the Leading Space Schools Education Programme – access to the Faulkes Telescope came as part of that package. I booked a couple of sessions on it myself, and once I’d worked out how to use it I explained to the students that in the professional world this was how astronomers gained access to some of the largest telescopes, booking time on

them and knowing exactly what they want to do beforehand.

asteroid, we were tracking in the shortest possible time.

What kinds of projects have the students undertaken using the Faulkes Telescopes? We had an opportunity this year to take part in what’s called a priority observation – an opportunity to observe something that could be cutting edge. Different schools around the country where given exact coordinates and exact exposure times for a capture. The schools also took different slots throughout the whole day, so we became part of the national Faulkes team. We were working alongside other telescope operators around the world in order to gather as much data about the object, a possible comet or

How has this access beneﬁtted the students at your school? It’s teaching them how to use remote controlled equipment: getting them to appreciate that although it might be 2pm on a summer’s day, they are operating a telescope on the other side of the world. Hopefully it will encourage them to do some research for themselves. The project helped them to develop an understanding of optics too. They found out the focal length of the telescope, its aperture and all those factors. Then, knowing what camera was attached, we worked out exactly what ﬁeld of view it covered.

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74 REMOTE TELESCOPES MARCH

© UNIVERSITY OF BRADFORD X 3

Þ My ﬁnal processed wide-ﬁeld shot of the Andromeda Galaxy, taken with the Cluster camera using a 90,000-millisecond exposure > of tabs that allowed me to adjust tone and contrast, ﬂip the image, correct and realign colours, and carry out photometry, among other things. Once saved, you can access your images at any time. It’s worth opening them in a separate image editing programme such as Photoshop, GIMP or Paint.NET to give them a ﬁnal touch up. I used Photoshop to make a few simple changes to my images, adjusting the colour balance, hue, saturation, brightness, contrast, and sharpness. Using a robotic scope is a fantastic way to get involved with astrophotography

Þ I managed to get a better glimpse of M31’s core in my narrow-ﬁeld shot using the Galaxy camera, set at an exposure of 100,000 milliseconds

without investing heavily in expensive equipment. And for more experienced imagers, robotic scopes offer a lot, providing raw data from which advanced processing techniques can bring out amazing detail. It may seem that being limited to a ﬁnite number of exposures per month is somewhat inhibiting in comparison to using your own scope. But when I took into account unpredictable weather – particularly here in the UK – the time it takes to capture image data yourself and the buzz of getting to use professional equipment, I found I was hooked. I think I’ll be giving it another go. S

Þ I also managed to produce a reasonable image of the Orion Nebula in a later session

ROBOTIC TELESCOPES

BRADFORD ROBOTIC SCOPE

ITELESCOPE.NET

OBSERVING WITH NASA

LIGHTBUCKETS

www.telescope.org

www.itelescope.net

www.lightbuckets.com

The Bradford Robotic Telescope offers two subscription packages. Standard subscription allows for a maximum of 10 jobs per month; Pro subscription gives greater access to the site and includes 40 images per month.

iTelescope.net can connect you with any of the 13 robotic scopes in its network, spread across the US, Spain and Australia. These include scopes as large as 20 inches and some of the world’s premier dark-sky locations.

http://mo-www.harvard.edu/ OWN/index.html

Price: Standard subscriptions £3 per month, Pro subscription £10 per month.

Price: Check online. Prices depend on image time, not exposures, ranging from free to over £500.

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Funded by NASA, this free service was developed by scientists at the Harvard-Smithsonian Center for Astrophysics to give schoolchildren the chance to observe the Universe. Now anyone can visit the website and use the MicroObservatory to image the cosmos. Price: Free

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LightBuckets provides access to ﬁve scopes; it will suggest which one you need for the job you request. Observing slots are rented by the hour and paid for with a points system. The most expensive scope, a 33-inch Nasmyth-Cassegrain, costs 350 points; the cheapest just 50. Price: Points start at $1 each, but the price drops the more you buy.

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The UK’s Telescope & Equipment Specialists Call 01223 911150 (local rate) for friendly advice and phone order

Great Service and Best Prices We offer a wide range of telescopes and accessories for all your star-gazing needs, beginners and experts alike, at our best prices – with free shipping (orders over £50 in UK mainland)

We are official dealers for Get expert, friendly advice to select the right equipment for your requirements. 01223 911150 | www.astronomycentre.co.uk | [email protected] WorldMags.net

ADVERTISEMENT FEATURE

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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. PLANET EARTH EDUCATION

UNIVERSITY COLLEGE LONDON

Courses available for enrolment all year round One of the UK’s most popular and longest standing providers of astronomy distance learning courses. Choose from ﬁve separate astronomy courses, suitable for complete beginner right through to ﬁrst-year university standard, including GCSE Astronomy. A certiﬁcate is issued for each completed course. You will ﬁnd a complete syllabus for each of the courses available, along with other details about each course, and the necessary enrolment information on our website. There is a ‘Student Feedback’ link where you can view some of the unsolicited comments we have received from past students. We pride ourselves on being accessible and ﬂexible and offer very attractively priced services, of the highest standards, and we work hard to provide you with what you want. Of paramount importance to us is the one-to-one contact students have with their tutor, who is easily accessible even outside of ofﬁce hours.

0161 653 9092 www.planeteartheducation.co.uk

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. Details and application form are linked on the web page below.

020 7679 3943 [email protected] www.ucl.ac.uk/phys/admissions/certificate WorldMags.net

ADVERTISEMENT FEATURE

WorldMags.net UNIVERSITY OF THE UNIVERSITY OF CENTRAL LANCASHIRE YORK

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 single-module 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.

MPhys (4-year) and BSc (3-year) degree programmes including Physics with Astrophysics. The astrophysics options and research project enable you to pursue in-depth knowledge of astrophysics topics. Programmes include hands-on experience using the Department’s suite of optical and radio telescopes. Key teaching and research areas include nuclear astrophysics, fusion and lasers, nanotechnology, computational and theoretical physics.

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

01904 322241 www.york.ac.uk/physics

Further details are available at: astro.qmul.ac.uk/teaching/ msc-astrophysics. Enquiries: [email protected] Tel: 020 7882 6958

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Skills

Brush up on your astronomy prowess with our team of experts

Contents The guide

How to

Sketching

Scope doctor

78

81

85

87

What can we learn about stars based on their colour?

Build a protective and insulating case for your powertank

Discover how to sketch M101, the Pinwheel Galaxy

Steve Richards answers your astro equipment queries

SKILLS

The guide With Elizabeth Pearson

The secrets of star colour We ﬁnd out what, if anything, we can tell about a star from its hue

THINKSTOCK X 2, ILLUSTRATION BY ESO/STEVE MARSH

S

imply standing outside on a clear night and looking at the stars is one of astronomy’s simple pleasures. Shining bright, they trace out the constellations and the myths of days gone by in vivid colour. In Orion, ﬁery red Betelgeuse squares off against blue-white Rigel; in Scorpio, Antares burns with a crimson intensity that led to its name, meaning ‘rival of Mars’. Elsewhere, the kaleidoscope spans rich golds, warm oranges and glinting sapphires. Stars give off light because their intense heat causes them to glow. The fact we see different colours is down to each star’s surface temperature: the hotter it is, the bluer the light it emits. Surface temperatures greater than 10,000°C will cause a star to appear blue. Those with lower temperatures will appear whiter, colder still will look yellow and stars as ‘cool’ as 3,500°C will look red or orange. Though our Sun appears yellow, and there are many yellow stars, its temperature of 6,000°C means that it is actually classed as white. All stars are predominantly made up of hydrogen and helium, plus traces of a few other elements, so it can’t be their composition that determines their temperature. Instead it’s their mass that makes the difference. More massive stars burn hotter, as the intense gravity makes

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star, we cannot use it to estimate mass. But there is a clear relationship between a star’s colour and its luminosity. This can be clearly seen on what’s known as a Hertzsprung-Russell diagram, an example of which is shown on the right.

The colour cascade

Þ The fact that stars can be different colours is most easily seen in the constellation of Orion their centres incredibly dense. This causes hydrogen fusion reactions within the core to happen much faster than in less massive stars, resulting in huge temperatures. Although colour can give us a rough idea of the surface temperature of a given

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The diagram is a scatter chart, with luminosity (either true or relative to the Sun) plotted against surface temperature. A couple of trends are immediately obvious, chieﬂy that blue stars occupy the left of the chart, red stars the right, with the rest of the spectrum in between. What this reveals is how stars evolve. The band that runs diagonally down the diagram is called the ‘main sequence’. When a star ﬁrst bursts into life it will fall somewhere along this line, its colour and luminosity in effect determined by its mass, which remains relatively unchanged throughout its life. Stars of all colours are being created all the time. Stars leave the main sequence when they begin to run out of fuel, a change that often results in the star changing colour too. Stars with masses between 0.3 and eight times that of the Sun move onto the ‘red giant’ branch. Their outer layers balloon out, causing the surface to rapidly cool. They still have the same mass as before, and are just as bright, but now have a

SKILLS MARCH 79 WorldMags.net 106

105

104

LUMINOSITY (compared to the Sun)

103

102

10

THE MAIN SEQUENCE Stars spend most of their lifetimes in this section. During their lives stars brighten slightly, which is why the band is so broad.

1

SUPERGIANTS The most massive of stars end their lives as supergiants. They are big enough to start fusing heavy elements in their cores, making them burn brighter and faster than any other stars.

The Sun

GIANTS

10 –1

10 –2 WHITE DWARFS

10 –3

10 –4

Interstellar winds eventually blow off the outer layers of red giants, leaving behind the tiny core as a white dwarf. The temperature of these stars is not a result of nuclear fusion, but the residual heat of their previous incarnation.

At the end of their lives, very massive stars suddenly redden and brighten, moving onto this branch. Though their diameter greatly increases, they still retain the same mass as before.

10 –5

30,000ºC

10,000ºC

6,000ºC

3,000ºC

SURFACE TEMPERATURE Þ Early versions of the Hertzsprung-Russell diagram plotted spectral class on the bottom axis, which is why the temperature scale now runs backwards different colour. When stars greater than eight solar masses run out of fuel, a similar thing happens and they become supergiants.

Sadly, hue alone can’t tell you if a red star is a supergiant or a red dwarf, or if it was born one million years ago

WHY DON’T WE SEE ANY GREEN STARS? You may have noticed that there are no green stars on the HertzsprungRussell diagram. In truth, there are lots of green stars, but to us they look white. Stars emit light at all wavelengths, but red stars emit much more red light than green or blue, which is why they appear that colour. It’s a similar story for blue stars. However white stars, such as our Sun, emit most strongly at green wavelengths, but nearly as much

red and blue is emitted as well. All put together it means the Sun, and other stars like it, shine white. Occasionally astronomers might ﬁnd a star that appears green, but this is most often an optical illusion caused by a nearby red star throwing off the eye. Zubeneschamali in Libra is often thought to be green even though it stands alone in the sky, however its spectral measurement classes it as a blue star.

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or has existed for billions. But colour can give us an indication of where a star may be on this evolutionary path – red stars are farther along the evolutionary chain than blue ones. Consequently, we can infer that places with a lot of blue stars must have formed them recently (astronomically speaking). Looking for blue stars, therefore, can reveal starforming regions both in our own Galaxy and beyond. It’s just one of the ways that astronomers can map out the stellar history of the Universe. As it turns out, star colour is much more than something that adds interest to the night sky. S Elizabeth Pearson is BBC Sky at Night Magazine’s staff writer skyatnightmagazine.com 2014

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SAN114F SAN114S SAN114TI

SAN114

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SKILLS MARCH 81 WorldMags.net

SKILLS

How to

Build a powertank protector With Mark Parrish

A simple battery insulator that doubles as an observing stool

It’s easy to customise this design: here we’ve added a cable tidy and hot water bottle compartment; inset, the unit in action

TOOLS AND MATERIALS

FINISH

Primer and oil-based paint, or varnish. MATERIALS

Plywood (12mm thick for sides and base, 6mm thick for front panel, back panel and lid layers), 18x18mm softwood batten, 50mm-thick foilcovered insulation foam, 50mm-thick sponge foam for seat, fabric offcut. SUNDRIES

No 8 woodscrews to secure battens, M5 countersunk bolts and nuts to secure lid layers, PVA glue, duct tape.

ALL PICTURES: MARK PARRISH

P

owertanks are portable battery packs that provide convenient and safe power for telescope mounts and accessories. Unfortunately in cold weather battery performance diminishes, so in this month’s How to we’re going to describe how you can build an insulating unit for your powertank – a unit that happens to double up as a seat. Typical batteries are designed to operate most efﬁciently at about 20-25°C. As temperatures fall, so does battery capacity – in other words, the amount of electricity they are able to hold decreases. The cycle life, the number of times the battery can be charged and discharged before it stops working properly, is similarly affected. If the temperature falls to –20°C, a battery may stop working altogether. Our seat unit insulates a previously warmed battery from the cold air outside,

TOOLS

Coping saw or similar, drill, ruler, compass, pencil, scissors, staple gun, craft knife, screwdriver, sandpaper.

with an optional small source of heat – a hot water bottle – maintaining the temperature during extended observing sessions. After six hours outside in temperatures of 5°C, our box was still a toasty 30°C inside. There are many models and types of powertank on the market and as such it is impossible to set out the best dimensions for your insulating unit here. Instead, you’ll ﬁnd an Excel calculator to help you work out the size of each part on the coverdisc. On the ﬁrst tab, marked ‘Calculations’, enter the length, width and height of your powertank and the other necessary details.

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Updating each ﬁeld recalculates the table of parts shown at the bottom of the sheet. This information is duplicated on the second tab, marked ‘Cutting list’, which you can print out and take to a timber merchant should you wish.

Design speciﬁcs The simple ‘screwed and glued’ design provides plenty of strength and makes this insulating unit relatively easy to build. One element worth expanding on, however, is the lift-off padded seat. It consists of two thin layers of plywood, which are screwed together. Before joining them, the upper > skyatnightmagazine.com 2014

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82 SKILLS MARCH

Seat padding

Lid panels; battens ﬁxed to long edges of lower lid

STEP-BY-STEP GUIDE

Gap at top accommodates lid batten

Back panel

Front panel Three battens ﬁxed to the exterior of the front and back panels

Side panels Base panel

ALL PICTURES: MARK PARRISH

Þ The ‘glue and screw’ nature of the protector makes assembly a straightforward affair > layer is topped with sponge foam and a PVC coated fabric. The edges of the fabric are tucked under the plywood layer (much like making a bed), pulled tight and stapled. When the bottom layer of plywood is attached the tucks and edges are concealed. To insulate the main unit, we used 50mm-thick foil-coated foam, the type used for cavity wall insulation in buildings. You can get this from builders merchants, but substitutes include plain polystyrene foam (we suggest sticking thin card or vinyl to this to prevent the delicate, crumbly surface from being damaged), bubble wrap or even loose foam packaging pellets. If you mix the latter with some PVA glue and ﬁll the space around an inner liner, they will set and stay together rather than shifting and settling. The resulting seat unit is necessarily bulkier and heavier than the powertank alone, but the shaped handles make it quite easy to carry. You may wish to add a shoulder strap if you have to move it long distances, but for garden use or when transporting it by car it is quite convenient and you no longer have to remember to pack a folding chair. We added a cable slot and some pegs so that leads and cables can be plugged in then coiled up on the outside of the unit ready for use – this means you won’t have to open up the warm chamber and let out heat to retrieve them. You may decide to add other features such as an eyepiece rack, or even build a second, uninsulated seat for other accessories or a fellow stargazer. S

Mark Parrish is a consummate craftsman who loves making astro accessories skyatnightmagazine.com 2014

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

STEP 6

Carefully mark out and cut the plywood panels to size. You should have seven: two matching side panels, matching front and back panels, two matching panels for the lid and one for the base. Cut the eight battens to length.

Cut out the handle slots by drilling holes at both ends and using a coping saw to complete the shape. Drill clearance holes for the screws, and countersink as shown above. This allows the screw heads to sit ﬂush with the surface.

Glue the four M5 bolts into the holes in the upper lid panel – we’ll come back to them shortly. First, make the seat. Place your seat padding on top of the upper panel, wrap your fabric over the top of the padding, then staple it to the underside of the panel.

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Mark out the screw holes. For the battens, you need three holes per batten in each surface it attaches to. Also mark out four extra holes in the upper and lower lids (which we’ll use to ﬁx these panels to each other) and the slots for the carry handles.

Glue three battens to the front panel and secure with screws; repeat for the back panel. Glue and screw the side panels and the base into these battens, and you should end up with a case like the one above. Fix the remaining two battens to the lower lid panel.

Fasten the upper and lower lids together by threading nuts onto the M5 bolts from the previous step. Sand all the surfaces and apply a protective ﬁnish. Finally, cut out and insert the insulating material into the main unit; ﬁx in place with duct tape.

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WorldMags.net Sussex Astronomy Centre Meade Advanced Product Dealer

Free Parking Friendly personal service for ALL your astronomy needs. $FMFTUSPO 4LZ8BUDIFS .FBEFNBJOTUPDLJTUGPS4VTTFY Beginners most welcome! A large range of telescopes and accessories from the world’s leading suppliers. Tel: t.VMCFSSZ-BOF (PSJOHCZ4FB 8PSUIJOH 8FTU4VTTFY

www.sussex-astronomy-centre.co.uk

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SKILLS MARCH 85 WorldMags.net

SKILLS

Sketching The Pinwheel Galaxy

With Carol Lakomiak

NEED TO KNOW STEP 1 Centre M101 in your eyepiece. Lightly coat the tip of a blending stump with B graphite and use it to draw a small spot (the galaxy’s core) in the middle of your sketch. With the B pencil, add the brightest stars in the ﬁeld – these are your anchor stars.

NAME: The Pinwheel Galaxy, M101, NGC 5457 TYPE OF OBJECT: Galaxy CONSTELLATION: Ursa Major RA: 14h 03m 12s DEC: +54° 20’ 53” EQUIPMENT: 8-inch or larger reﬂector; H and B pencils; blending stump BEST TIME TO SKETCH: 1-4 March, 8pm UT till dawn; 21-30 March, 8pm UT till midnight FIELD OF VIEW SHOWN: 44 arcminutes; 109x magniﬁcation

ALL PICTURES: CAROL LAKOMIAK

F

ace-on spiral galaxy M101 was discovered in March 1781 by Pierre Méchain. Its magnitude is listed at +8.4, but it’s actually quite dim because of something called ‘surface brightness’. In a nutshell, surface brightness is the result of evenly distributing the magnitude of an object over its entire size. So, M101’s magnitude of +8.4 is actually spread out over an area of 21x21 arcminutes, making the galaxy appear much dimmer than its magnitude might suggest. As such, it’s best sketched under as dark skies as you can ﬁnd. To locate M101, imagine an equilateral triangle with a base formed by mag. +2.2 Mizar (Zeta Ursae Majoris) and mag. +1.9 Alkaid (Eta Ursae Majoris). The galaxy is where the top of the triangle would be. Because of its dimness, it helps to study M101 at low magniﬁcation before you start your sketch. Using averted vision, determine where the edges of the galaxy lie relative to the nearest anchor stars. When you do start sketching, use large circular motions with your ﬁngertip to create the galaxy’s glow. Then increase

the magniﬁcation to look for galactic structure – the background glow might fade a bit when you increase the power. Using averted vision, scan around and see if you can detect any bright areas or hints of the spiral arms. If you do, draw them with the graphite-coated blending stump – use a light touch and very small circular motions. The anchor stars you draw in Step 1 will help you to populate the star ﬁeld; they also serve as a ‘frame’ to keep the view centred if your telescope doesn’t have tracking. If this is the case, all you have to do to counter the Earth’s rotation is reposition your scope so that the anchor stars in the eyepiece match those in your sketch. Stars often form shapes in the eyepiece, some geometric, others random but pleasing to the eye. Note down any that you see and use them, along with the anchor stars, as guides to ﬁlling in the rest of the star ﬁeld. As a ﬁnal step, invert your sketch in an image-editing program. Carol Lakomiak is BBC Sky at Night Magazine’s sketching expert

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STEP 2 Scribble some B graphite on a piece of paper and rub your ﬁngertip across it a few times. Use your ﬁngertip to ‘draw’ the full size of the galaxy’s glow. If you detect any structure in the galaxy, such as spiral arms or bright patches, add them with the blending stump.

STEP 3 As you populate the star ﬁeld with an H pencil, look out for any shapes that could be used to help you determine the proper placement of other stars. For example, two of the anchor stars drawn in Step 1 are part of an triangle in the top right of the view.

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SKILLS MARCH 87 WorldMags.net

SKILLS

Scope

With Steve Richards

DOCTOR

Our resident equipment specialist cures your optical ailments and technical maladies

PAUL WHITFIELD X 2

I recently bought a Canon EOS 5D Mk III DSLR camera. What portable equipment is available to start my astrophotography journey? JUSTIN WALKER The Canon EOS 5D Mk III is capable of taking some great images of deepsky objects, although it is less suitable for Solar System imaging, where a high frame rate camera would be better. Here are a couple of portable options for you. You could use your new camera with a selection of lenses to capture wide-ﬁeld images, and here there are several ultra-portable mounts that you could consider. The AstroTrac TT320, for example is extremely lightweight at only 1kg, yet has a payload capacity of 15kg making it suitable for mounting a wide range of lenses and refractor telescopes. If you like the idea of using camera lenses then the Vixen Polarie Star Tracker and iOptron SkyTracker are even more compact, but only have a payload capacity of around 3kg. Camera lenses with focal lengths in the range of 15mm to 200mm would be ideal. However, if you would prefer to get closer into the action then a larger mount will be required and either the Sky-Watcher HEQ5 Pro or Celestron Advanced VX mounts should be on your shortlist. Matched with either an ED doublet refractor like the Sky-Watcher ED 80 Pro or the new William Optics GT-81 triplet, you would have a formidable

imaging system. With either of these mounts you should consider autoguiding and – if you are using a telescope – adding a focal reducer-ﬁeld ﬂattener.

Þ AstroTrac’s TT320 is light, but easily capable of supporting a refractor

STEVE’S TOP TIP

limited How can I get the most out of my camera? CCD imaging time with my mono want to If your imaging time is limited but you mono CCD a with es capture detailed colour imag hydrogena just g usin ing camera, consider imag owband narr I) (OII III en oxyg an and alpha (Ha) sions is emis ﬁlter. Because the wavelength of OIII OIII the , light blue and right on the cusp of green blue and n gree the both data can be used for channel. channels, leaving the Ha for the red both green to Mapping the Ha to red and the OIII ly high nt, vibra and blue channels produces data! of sets two just with es detailed colour imag

I have a Celestron NexStar 5 SE Go-To telescope. Is there any type of motor maintenance that I should be doing? LO BARBOSA The Celestron 5 SE is a complete observing system comprising a Schmidt-Cassegrain and a computerised Go-To altaz mount with a simple built-in ‘wedge’ that allows the mount to be used in equatorial mode. In common with most other mounts of this type, like the Sky-Watcher SynScan AZ Go-To and the iOptron Cube-PRO Portable Go-To, user motor maintenance is not actually required Þ The NexStar as the units are pretty 5 SE benefits well sealed and should from minor only be opened for repair precautions by the manufacturer. However, there is some general maintenance and care that can be applied to all mounts of this type to help keep them in tip-top condition. Moisture and dust are the biggest potential enemies so always remove any moisture with a soft towel after each observing session. Store the mount in a dry, well-ventilated area and when it is completely dry, cover it with an old pillow case to keep dust at bay. Steve Richards is a keen astro imager and an astronomy equipment expert

Email your queries to [email protected] WorldMags.net

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REVIEWS MARCH 89 WorldMags.net

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

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

90

Find out if Borg’s modular astrograph is worth more than the sum of its parts

SEE INTERACTIVE 360° MODELS OF ALL OUR FIRST LIGHT REVIEWS AT WWW.SKYATNIGHTMAGAZINE.COM

WWW.THESECRETSTUDIO.NET X 4

This month’s reviews

First light

90

Borg 89ED f/4.3 modular astrograph

94

Celestron Skyris 445C colour imaging camera

98

Pentax Astrotracer DSLR camera kit

Books

Gear

102

104

We rate four of the latest astronomy titles

Including this Virgin Galactic model kit

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

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FIRST light

See an interactive 360° model of this telescope at www.skyatnightmagazine.com/borg89ed

Borg 89ED f/4.3

astrograph ALL PHOTOS: WWW.THESECRETSTUDIO.NET

VITAL STATS s Price £2,295 s Optics Doublet with one ED element s Aperture 89mm (3.5 inches) s Focal length 383mm, f/4.3 s Focuser FeatherTouch 2-inch dual-speed 10:1 Crayford s Extras 0.65x focal reducer-ﬁeld ﬂattener s Length 539mm including dew shield, 458mm without dew shield s Weight 2.8kg including tube rings s Supplier Ian King Imaging s www.iankingimaging. com s Tel 01580 212356

A self-assembly telescope aimed at intermediate imagers WORDS: STEVE RICHARDS

T

aking delivery of a Borg refractor is a most unusual and surprising experience. There’s no long box: rather, the telescope is supplied in component form in several small boxes ready for ﬁnal assembly by the end user. This modular approach has advantages for both portability and upgradeability. Assembly was very straightforward, with each component mating accurately with the next. The parts supplied for this review form a very wideﬁeld astrograph; in other words, a telescope speciﬁcally designed with deep-sky imaging in mind. Looking at the optics, the objective lens was ﬁnely multicoated to increase light transmission and free of blemishes. We were originally caught out by a set of silver rings that had no internal or external threads in them. However, a little research revealed these to be simple spacers, one of which (the 4mm one) was vital to making sure that the camera attachment

couldn’t foul the protruding lens element at the rear of the two-part reducer-ﬂattener.

Finding focus In common with many other focal reducer-ﬁeld ﬂatteners, the spacing between the camera’s sensor and the mounting face of the reducer is set at 55mm. This measurement makes it compatible with a typical DSLR camera when using a Borgsupplied and camera-speciﬁc bayonet adaptor. Unfortunately, when not using a DSLR two adaptors must be used in the image train, eating into this spacing allowance by 13mm. Although this leaves sufﬁcient back focus for a typical CCD camera and ﬁlter wheel, there is insufﬁcient allowance for an off-axis guider as well, so autoguiding must be carried out using a separate guide telescope. We mounted the review telescope on our own side-by-side mounting bar and used a 4-inch refractor as our guide telescope. >

MODULAR ASSEMBLY The Borg 89ED is part of a highly modular range of telescopes designed very much with portability in mind. This modular approach allows you to upgrade components incrementally as your requirements change. It also makes transporting equipment very simple indeed: Borg telescopes are not only supplied in component form, but are designed to be dismantled again and taken overseas. It is, therefore, possible to carry just the critical components – such as the objective lens – in airline hand luggage while the rest of the instrument goes in the hold. Tube diameters are reduced in size to exactly match the light cone of the objective lens, and the other components are similarly matched to keep the telescopes as compact and lightweight as possible. The engineering of the various modules is very ﬁne indeed, and when it came to assembly we found that each part screwed smoothly into the next. Once assembled, the telescope felt solid but surprisingly light, with no obvious sign of its modularity.

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FIRST LIGHT MARCH 91 WorldMags.net

CAMERA ROTATOR It is important to be able to rotate the imaging camera to accurately frame your chosen object. The built-in camera rotator has three knurled thumb screws, which loosen a collar so you can spin the rear section through 360°. Re-tightening the collar after rotation resulted in zero image or focus shift.

FEATHERTOUCH FOCUSER The telescope is supplied with a FeatherTouch 2-inch dual-speed 10:1 Crayford focuser. This ﬁne focuser installs seamlessly into the telescope tube. The action is perfect, very smooth yet able to comfortably support the weight of our CCD camera. There was no focus shift when using the locking bolt.

DEW SHIELD The retractable dew shield has an aluminium screw-ﬁt dust cap and removable plastic centre disc, which forms an 81mm aperture mask. The dew shield extends by 81mm, offering the front element excellent protection from stray light and dew, but we would have liked to have seen a locking bolt.

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SKY SAYS… The objective lens was ﬁnely multicoated to increase light transmission and free of blemishes

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WorldMags.net FOCAL REDUCER-FIELD FLATTENER The 0.65x focal reducerﬁeld ﬂattener is designed to provide a wide and ﬂat ﬁeld of view. It is comprised of four elements, one of which is made from Ohara ED (extra-low dispersion) glass. Star shapes were generally excellent, with just a hint of elongation at the corners of the ﬁeld of view.

FILTER DRAWER The ﬁlter drawer unit is installed just before the rear section of the focal reducer-ﬁeld ﬂattener. The holder is easy to remove and accommodates 52mm or 48mm ﬁlters. To minimise disturbance, a standard mechanical shutter release cable with an M3.2 tapered thread can be used to eject the ﬁlter holder.

FIRST light > With its short focal length, this scope captures a ﬁeld of view 3° 20 arcminutes wide by 2° 13 arcminutes deep when used with a camera with an APS-C sized sensor. To put this into some kind of sky perspective, this ﬁeld of view would capture the whole of NGC 7000, the North America Nebula. Many other deepsky objects are also fairly large, so a wide ﬁeld of view like this is a very attractive proposition. Short focal length telescopes have a very narrow focus ‘sweet spot’, but with the precision FeatherTouch Crayford focuser supplied, achieving focus was a simple task. We also noted that there was no image shift when racking the focuser in and out and it had no difﬁculty supporting the weight of our CCD camera.

Detail leaps out of our image of the Horsehead Nebula in Orion

WWW.THESECRETSTUDIO.NET, STEVE RICHARDS

Broad testing We used a Starlight Xpress SXVF-M25C one-shotcolour CCD camera with an APS-C sized sensor for our imaging tests. To combat the effects of light pollution, we inserted a 2-inch Hutech IDAS light pollution ﬁlter into the focal reducer’s built-in ﬁlter drawer. This very useful feature, combined with additional ﬁlter holders available from Borg, could remove the need for a ﬁlter wheel when using a mono CCD camera to produce colour composite images. Among the deep-sky delights we imaged were the Pleiades and the more elusive Horsehead Nebula. These two objects and their surrounding areas encompass a star cluster, reﬂection nebulosity, dark nebulosity and emission nebulosity, giving us the opportunity to assess the telescope’s performance over a range of different objects and brightness skyatnightmagazine.com 2014

levels. Star shapes were good over the majority of the ﬁeld of view with just the tiniest amount of ﬁeld curvature making its presence known in the far corners. We were impressed with its performance and would recommend it to intermediate imagers looking for a wide-ﬁeld telescope. S

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

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+++++ +++++ +++++ +++++ +++++ +++++

SKY SAYS… Now add these: 1. QSI 683 WSG-8 CCD camera 2. Avalon M-Zero mount 3. Astrodon 31mm LRGB ﬁlter set

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We are ofﬁcial dealers for a range of quality brands including Celestron, Sky-Watcher, Baader Planetarium, Lunt, Altair Astro, iOptron, Kendrick, Vixen, Opticron, AstroTrac, ZW Optical and Barr and Stroud, all of which can be seen in our showroom. Check out www.tringastro.co.uk for our Latest Special Offers, Events, Monthly Sky-Guides, Buying Guides, Product Reviews and more, or visit our Showroom in Tring Hertfordshire - Open 6 Days a Week!

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FIRST light

See an interactive 360° model of this camera at www.skyatnightmagazine.com/celest445c

Celestron Skyris 445C

colour imaging camera USB 3.0 compatibility takes this camera’s imaging ability to new heights WORDS: MARTIN LEWIS

ALL PHOTOS: WWW.THESECRETSTUDIO.NET

VITAL STATS s Price £649 s Sensor Sony ICX445AQA colour CCD sensor s Pixels 1280x960 pixels, 3.75μm square s Size 42x42x39mm s Weight 94g s Extras 1.25-inch adaptor, C-mount to CS-mount adaptor, USB 3.0 cable, software CD, user manual s Software CD Drivers, iCap 2.3, RegiStax 6 s Supplier David Hinds s www.celestron.uk.com s Tel 01525 852696

T

he Imaging Source has paired with start recording. It is best to record videos in the Celestron to produce the Skyris monochrome Y800 format, as this saves disk space 445C. This colour CCD camera, with and improves connection speed. You can convert USB 3.0 connectivity and a 1280x960 the monochrome video to colour at a later date pixel Sony ICX445AQA chip at its heart, is designed using software such as RegiStax. At night we found for high-resolution imaging of the it best to set the record dialog box in brighter planets of the Solar System, as the preview screen to RGB32 colour SKY SAYS… well as areas of the Sun and Moon. for easier focusing, then change this This camera is Digital video cameras are often used back to Y800 before recording. designed for highto produce high-resolution still images of our nearest neighbours. To get stills resolution imaging from a device like this, the recorded On our newer Windows 7 laptop of the brighter videos are split into individual frames there were no real issues with running planets, as well and sorted in order of quality using with either USB type, frame rate as areas of the stacking software such as RegiStax or differences aside, but when using an Sun and Moon DeepSkyStacker. The best frames are older Windows XP laptop, which was then aligned, combined and sharpened USB2.0 only, iCap 2.3 crashed every to produce a detailed image. time we tried to adjust the gain setting slider. As The number of frames you have to work with here an alternative, we successfully used the camera depends on the frame rate, which is the number of with the latest version of freeware recording consecutive images (or ‘frames’) that your device program FireCapture. can capture per second. You can connect the Skyris Our ﬁrst imaging target was the ﬁrst quarter 445C to your computer through either a USB 2.0 or Moon, captured using a 8.75-inch f/6 Newtonian a USB 3.0 port, but a USB 3.0 connection is better as reﬂector, 2x Barlow lens and an ultraviolet/infrared it allows you to record at double the frame rate. ﬁlter screwed onto the camera’s 1.25-inch adaptor. The camera can be operated using the The Skyris 445C produced smooth images showing supplied iCap 2.3 software. This good detail over large regions, with the 1280x960 program allows you to alter chip running at 30 frames per second (fps). We the exposure, gain and wanted to experiment by lowering the camera’s other settings, and gamma setting for some of the higher-contrast >

In the ﬁeld

THE LATEST USB CONNECTIVITY The cameras in the Skyris range are some of the ﬁrst astronomical video cameras to utilise USB 3.0 connectivity for improved data transfer rates. When using iCap to record videos in the highest quality uncompressed monochrome format (Y800), the large chip size limits the maximum video frame rate at USB 2.0 to 15fps. However, with a USB 3.0 connection the camera can run at a maximum of 30fps. The advantage of this higher frame rate is that you can gather more video frames in a given time. When you come to process your videos, an increased number of frames helps to reduce signal noise in the stacked image, giving a smoother result. It also means that more detail can be pulled out when processing. You can still use the camera with USB 2.0 perfectly well – just not at the higher frame rates that USB 3.0 allows.

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FIRST LIGHT MARCH 95 WorldMags.net

COLOUR CHIP The Sony ICX445AQA CCD chip allows you to quickly record in full colour without having to capture separate red, green and blue videos through individual colour ﬁlters and recombining later on, as is the case with mono cameras. This speeds up the colour imaging process considerably and avoids the need to purchase a set of colour ﬁlters.

BODY The camera has a beautifully made and very neat aluminium housing, which is the about the size and weight of a mediumsized eyepiece. Heat dissipation ﬁns machined into the exterior of the body keep the chip cool, helping to minimise noise.

MANUAL The 15-page manual is worthy of comment as it is particularly well laid out and clear. It covers system requirements, driver and software installation, how to use the camera to capture videos and how to process them in RegiStax. There are also some useful general tips on digital video imaging.

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96 FIRST LIGHT MARCH

FIRST light 1.25-INCH ADAPTOR The kit comes complete with a 1.25-inch to C-mount adaptor, threaded for ﬁlters. This screws into the front of the camera so you can insert it into an eyepiece holder. Also included is a C-mount to CS-mount adaptor ring, should you wish to attach different video lenses directly.

USB 3.0 CABLE Some video cameras come with connector leads that are impractically short. Not so the Skyris 445C: its USB 3.0 cable is a generous 3m. The plug is secured to the body of the camera by two thumbscrews, preventing accidental disconnection, and is backwards compatible with USB 2.0 sockets.

SKY SAYS… Now add these: 1. Celestron infrared-blocking ﬁlter 2. Celestron off-axis guider

WWW.THESECRETSTUDIO.NET X 2, MARTIN LEWIS X 3

> lunar regions, but surprisingly the software has no

slider to change this. Jupiter was next on our list. To save hard disk space we set a reduced frame size of 640x480 pixels using the rather awkward ‘region of interest’ feature in iCap. The sensitivity of the camera was evident, however, and allowed short exposure times of 1/40th of a second. The ﬁnal processed images showed good belt and spot details on the planet, but we had to stick with 15fps as higher speeds showed a ghosting artefact, visible as an arc on one side of the planet after processing. The artefact was absent at 15fps but got worse the higher we pushed the frame rate. Our ﬁnal target was the winter Sun, low in the south at midday, imaged with a white light ﬁlter over our scope’s aperture. The fully processed images revealed nicely detailed sunspots, solar granulation and bright faculae. Again we covered large areas of the disc with the big chip and, unlike Jupiter, recording at 30fps didn’t lead to any ghosting. Like the Moon, this high-contrast object didn’t need much processing, which suppressed the artefact. If you are looking for a camera to have a go at producing your own detailed images of our near neighbours, you might well consider the Skyris 445C for its large colour chip and USB 3.0 connection. S

3. Baader Microguide eyepiece

> The south polar region of the Moon at ﬁrst quarter, recorded at 1280x960 pixels and 30fps

Þ The main belts were clear on Jupiter, captured at a smaller frame size of 640x480 pixels and 15fps

VERDICT BUILD AND DESIGN CONNECTIVITY EASE OF USE FEATURES IMAGING QUALITY OVERALL skyatnightmagazine.com 2014

+++++ +++++ +++++ +++++ +++++ +++++

> Sunspots stood out on the white light Sun, imaged at 1280x960 pixels and 30fps

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FIRST light

See an interactive 360° model of this camera at www.skyatnightmagazine.com/penastrokit

Pentax Astrotracer

DSLR camera kit M

A package that promises star tracking without the need for an equatorial mount

WORDS: MARK PAYNE-GILL

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VITAL STATS

s Price Package £1,995; Astrotracer only £229.95 s Camera Pentax K-5 IIs DSLR s Lens 16-50mm, f/2.8 s Camera sensor CMOS type APS-C s O-GPS1 weight 61g including battery s Tracking duration Up to ﬁve minutes s Supplier The Widescreen Centre s www.widescreencentre.co.uk s Tel 020 7935 2580

any of us start out in astro imaging Calibration’ procedure, which is crucial to enable with a simple setup: a DSLR with a the tracking function. The display instructed us to bulb function and a tripod. Under rotate the camera body for 180˚ or more around the dark skies and with short exposures, horizontal, vertical and lens axes. After 30 seconds this modest equipment will allow you to record or so an ‘OK’ message conﬁrmed calibration was simple but pleasing views of the Milky Way and successful and defaulted back to the Astrotracer individual constellations, revealing menu, where we set the exposure time. detail beyond the reach of the eye Clicking the ‘Start Shooting’ ﬁeld then SKY SAYS… alone. However, as you take longer prompted us to press the shutter It is impressive exposures, the menace of Earth’s release to initiate the Astrotracer and in its ability to rotation takes hold and turns start the exposure. pin-sharp stars into trails. compensate for In recent years a number of Earth’s rotation, compact, portable products have With the supplied lens set to its even after appeared on the market as a solution widest at 16mm, we began with a two minutes for tracking the sky without the need one-minute exposure, gradually for a bulky equatorial mount. Pentax’s increasing to the ‘maximum trace offering is the Astrotracer O-GPS1 unit – a device duration’ of ﬁve minutes to see how well it coped at that tracks the sky through a DSLR camera by the extreme end of its tracking range. We then physically adjusting its mirror. switched to the longest focal length of 50mm and The package we review here comprises Pentax’s did the same. The supplied wireless shutter release ﬂagship K-5 IIs DSLR camera body, a 16-50mm button activates the mirror-up function and opens f/2.8 lens, a wireless remote control and the O-GPS1 the shutter a few seconds later: a very useful feature unit. After switching on the camera and GPS unit, to minimise camera shake. the Astrotracer function is accessed via one of ﬁve After one minute the Astrotracer was coping submenus in the main shooting display. This is well with tracking and after two minutes little well explained in the manual. tracking error was evident. However, in threeWith focus set to manual and exposure mode minute exposures the stars at the top and bottom to bulb, we selected the ‘Astrotracer’ mode from corners appeared as trails, but peculiarly the the GPS menu. We then followed the ‘Precise centrally framed stars were still small points. >

Trail thresholds

FROM DAMPING TO TRACKING The Astrotracer function is a great example of converging technology where one application gives rise to another: in this case the camera’s built-in shake reduction system, which uses magnetic and acceleration sensors to dampen vibrations during normal handheld photography. Cleverly, the Astrotracer function is able to use information from these sensors to generate alignment data in three axes. When combined with GPS latitude data, it calculates the movement of celestial objects as Earth rotates.

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Once activated it is able to physically move the camera sensor to compensate for this motion. Although the range through which the sensor physically moves is small, it is still large enough to translate into relatively long exposure times without trailing, far longer than a camera ﬁxed on a tripod can possibly achieve. As such, it opens up a range of possibilities for travellers who are interested in astrophotography, but don’t want to be burdened with large pieces of equipment.

FIRST LIGHT MARCH 99 WorldMags.net

LENS In optical terms the supplied lens performed adequately while wide open at f/2.8, with some aberration noticeable at the edges of the frame. You could also use manual lenses, but you will have to input its focal length data for the Astrotracer to function correctly.

O-GPS1 UNIT Light and compact, the body of the GPS unit simply attaches to the hot shoe on top of the camera, requiring its own power source with a single AAA battery. It gives GPS positioning data on screen and can even be used as a navigation aid.

TOP DISPLAY An exposure countdown timer activates on the top display of the camera when the Astrotracer is enabled. The display has a bright green backlight, which you’ll need to turn off if you want to keep your night vision. The main menu needs to be accessed to toggle this on and off.

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100 FIRST LIGHT MARCH

FIRST light SENSOR The K-5 IIs uses a CMOS type APS-C format sensor with an ISO range from 80 to 51,200. We took test shots to check its sensitivity and noise handling at higher ISO ratings: this was good up to ISO 800. Noise crept in at ISO 1600, above which it became very noticeable.

SKY SAYS… Now add these: 1. Horizon 8115 two-way tripod

3. Meade astro rucksack

þ Our one-minute exposure of Orion, captured at ISO 800 and a 50mm focal length

> Recalibrating the sensors failed to correct this.

CAMERA

Stars move larger distances across the sky the closer they are to 0˚ declination, which combined with the curvature of the wide-angle lens could explain the apparent trailing. The ﬁve-minute exposure showed noticeable trailing in the centre and was much worse at the edge of frame. The Astrotracer appeared to have gone beyond its limit at this focal length. Focusing on Orion, we repeated these tests with the lens at its longest focal length, 50mm. In one-minute exposures, stars were small points of light with good detail recorded in the Orion and Flame Nebulae, although on the right of frame there was a little ‘bloating’ of stars, which looked more akin to lens aberration than poor tracking. The Astrotracer continued to do a good job after two minutes, with Orion standing out beautifully, although stars at the edge of the frame were beginning to trail. In longer exposures the

The camera itself is lightweight, of good build quality and weather-sealed, with a sensor designed to perform well in low light conditions. The viewﬁnder gives 100 per cent coverage and we found the menu easy to navigate. With a ﬁrmware upgrade Pentax’s K-5 and K-r cameras can also support the GPS unit and Astrotracer function.

Astrotracer struggled to keep sync, with the stars appearing trailed right across the image frame at ﬁve-minute exposures.

All things considered... Given that it only takes 10 seconds for stars to trail in photographs taken on a ﬁxed camera with a 50mm lens, the Astrotracer is quite impressive in its ability to compensate for Earth’s rotation, even after two minutes. It will appeal to those new to astro imaging, and for those on a budget it performs well enough for wide-ﬁeld imaging to serve as an alternative to expensive standalone tracking platforms. Equally, this is a clever piece of kit to have tucked away if you want to travel without lugging a tracking platform around. It should be noted that the Astrotracer unit itself can only be used in conjunction with Pentax DSLRs that have the magnet-driven Shake Reduction system, such as the K-5 IIs, K-5 or K-r. S

VERDICT ASSEMBLY BUILD & DESIGN EASE OF USE FEATURES TRACKING ACCURACY OVERALL skyatnightmagazine.com 2014

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WWW.THESECRETSTUDIO.NET, MARK PAYNE-GILL

2. Tracer 10Ah lithium polymer battery pack

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

Gransden, Beds & Cambs SG19 3PF 01767 677025

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Books New astronomy and space titles reviewed

An Astronaut’s Guide to Life on Earth B

NASA, NASA/VICTOR ZELENTSOV

Chris Hadﬁeld Macmillan £18.99 z HB

You can order these books from our shop by calling 01803 865913

TWO MINUTES WITH CHRIS HADFIELD

OOK

OF THE MONTH

Canadian astronaut Chris Hadﬁeld became a YouTube sensation when he performed a version of David Bowie’s Space Oddity from aboard the International generation of space voyagers is not easy for someone driven to succeed. Space Station. Now we can read about There is a lazy assumption that astronauts the rest of his remarkable career, both are unemotional robots, and this is why on Earth and off it. In 1995 he took they can perform so well in conditions that part in a joint docking mission between would frighten the life out of most of us. Space Shuttle Atlantis and the Hadﬁeld insists the opposite is Russian space station Mir. true. If you try to be a decent Six years later, he helped and happy person on assemble the ISS. And Earth, you will be a in 2013, he commanded better one in space, too. the station after If there is one ﬂying to orbit aboard slight ﬂaw in this a Soyuz capsule. book, it’s the lack of Among the many supporting characters. adventures recounted Hadﬁeld is the focus is a spacewalk in throughout, which is which Hadﬁeld was mainly to its beneﬁt, temporarily blinded by but just occasionally, its excess cleaning ﬂuid inside undoing. Even so, this ﬁnely his helmet visor. Blinking back the discomfort, he Hadﬁeld says his social written account should appeal media efforts were part to anyone with an interest in continued with his tasks of being an explorer space travel. It’s a reminder, regardless. Incidents such as too, that enthusiasm, commitment and this reveal the seemingly unstoppable hard work can get you where you want to willpower shown by all astronauts. It’s go, so long as you remember to take time not entirely wrong to describe them off with the kids once in a while. as superhuman, but Hadﬁeld points out that you have to hold onto your ★★★★★ ordinary, earthbound qualities, too. Maintaining the love of your family PIERS BIZONY is the author of The Space when you’re hardly ever at home, Shuttle and other books on spaceﬂight protecting friendships in an intensely competitive job and keeping your sense Reader price 17.99, subscriber price 16.99 of humility when training up the next P&P £1.99 Code: S0314/1 skyatnightmagazine.com 2014

RATINGS ★★★★★ Outstanding ★★★★★ Good ★★★★★ Average ★★★★★ Poor ★★★★★ Avoid

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What inspired you to write the book? It’s really the expression of what I’ve been doing for the past 21 years as an astronaut, the incredible experience of spaceﬂight and the perspective that it brings. I decided that the name of the book should be An Astronaut’s Guide to Life on Earth because that’s what really matters to everybody. I ﬂew in space very rarely in my time as an astronaut. Almost everything that was fun and interesting occurred on Earth. Why was it important for you to share your experience through social media? Not only did I try to do my job right, try to be competent and do everything I needed to do, but a large component of the work was to bring everybody along on the voyage to the best of my ability – and to the best of our technology’s ability. For anybody who is walking on the forefront of exploration on behalf of other people, a large part of the job is to bring the messages back. The advent of huge advances in technology allowed me to communicate in a more effective way. What is the most important lesson you learned as an astronaut? You have to have a life with purpose. To have long-term goals for yourself, things you want to do with your life but don’t make them the deﬁning characteristic of your life. The real joys of life have been on a day-to-day basis. I have a purposeful life but at the same time love every rung of the ladder or every step along the way. CHRIS HADFIELD is a former commander of the International Space Station

BOOKS MARCH 103 WorldMags.net

From Dust to Life John Chambers and Jacqueline Mitton Princeton £19.95 z HB We may all be made of stardust, but the mystery of the origin of this dust has intrigued people since the dawn of time. In From Dust to Life: The Origin and Evolution of our Solar System the authors attempt to solve the riddle – with a great degree of success. John Chambers and Jacqueline Mitton take us on a journey through space and time in our planetary neighbourhood. In an accessible and engaging manner, they combine astronomy, astrophysics, history and space exploration, not only telling us what happened but explaining the science behind it. Complete with pictures, tables and diagrams, the book at times reads like a school manual – but not in a dreary way.

The Cosmos: Astronomy in the New Millennium Jay M Pasachoff and Alex Filippenko Cambridge £40 z PB The Cosmos: Astronomy in the New Millennium is an excellent textbook that provides an introduction to modern astronomy. It is extremely wide ranging: the initial chapters give a good introduction to light, energy and matter, the essential prerequisites of modern astronomical tools like spectroscopy. Optics and telescopes are also discussed. All of the standard astronomical topics are covered here in a nice order, starting from celestial mechanics and the Solar System, and then on to stellar evolution and cosmology. Harder topics like black holes are given a nontechnical treatment.

It is incredibly thorough and detailed, yet very accessible to non-scientists too. The narrative ﬂows nicely from chapter to chapter, ﬁrst winding the clock back to see how our ancestors tried to explain what they saw above their heads, and then meticulously listing all the major recent discoveries. Not only does the book tell us how old the Earth and the Universe are, it also explains the various past calculations. At times, though, the authors mention things that may not be known to a general audience without any follow-up – one example that sticks in the mind is that of the Oort Cloud. Granted, there’s a glossary in the end that has the deﬁnition, but to know about the glossary, one would have to study the contents or leaf through the book backwards. Not everyone does. Nonetheless, this remains a compelling overview of the evolution of the Solar System.

★★★★+

KATIA MOSKVITCH is a science writer and broadcaster Reader price 16.99, subscriber price 15.99 P&P £1.99 Code: S0314/2

A reasonable amount of space is given to more recent topics like SETI, the Search for Extraterrestrial Intelligence. Refreshingly, the book also includes the exploits of amateur astronomers and provides some good context for many of the historical ﬁgures who have helped to shape astronomy over the years. Personally I would have liked to have seen a few more worked examples, in particular those of a more mathematical nature, as these often present students with the most difﬁculties. The book is well structured and illustrated, and the authors have taken great care to get salient points across efﬁciently. Key ideas are summarised at the end of each chapter, and I was pleased to see a discussion on the nature of science and the scientiﬁc method – the philosophy of science is something all students should explore as soon as possible. All in all, a helpful introduction to anyone studying astronomy today.

★★★★+

DR PAUL ABEL is a reporter on The Sky at Night on BBC Four

The Constellation Observing Atlas Grant Privett and Kevin Jones Springer £26.99 z PB When it comes to ﬁeld use, full-sized star atlases are unwieldy and pocket atlases often too small. Thus there’s a vacant niche in the market for a textbook-sized tome like this one. The Constellation Observing Atlas is an alphabetical list of constellations, each with a chart, description, historical and mythological notes, and a varied selection of objects that can be seen with apertures as small as three inches. The authors’ familiarity with their choice of objects, coupled with interesting asides, makes the constellation notes a pleasure to read. They also make occasional helpful recommendations of better targets in adjacent constellations. The constellation genitives are wrong in a few instances, but this is a minor error we all occasionally make. Unfortunately there are several larger oversights that limit the charts’ usefulness for inexperienced observers. None of the charts have constellation names on them, and there’s no consistency as to whether the chart is printed opposite or on the reverse of its accompanying notes. The charts are also reproduced at different scales, and sometimes with no indication of the scale. Nor are there any index charts to show how the constellations ﬁt together. The blue chart background helps to preserve dark adaptation when used under red light, but we found that the black text became difﬁcult to read and the green symbols for planetary nebulae disappeared altogether. Still, this could become a useful book for beginners if future editions address its shortcomings.

+++++

STEPHEN TONKIN writes BBC Sky at Night Magazine’s Binocular tour Reader price 23.99, subscriber price 22.99 P&P £1.99 Code: S0314/3

Reader price 34.99, subscriber price 33.99 P&P £1.99 Code: S0314/5

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104 GEAR MARCH

Gear

Elizabeth Pearson rounds up the latest astronomical accessories

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4 1 Altair 20mm Lightwave Hyperwide 100˚AFOV Eyepiece Price £339 s Supplier Altair Astro 01263 731505 swww.altairastro.com This eyepiece provides a massive 100º apparent ﬁeld of view (AFOV). It’s rather weighty at 875g, but has 14.5mm eye relief and a folding rubber eye guard.

2 Warmawear Heated Socks Price £14.95 s Supplier Primrose 0118 903 5210 s www.primrose.co.uk These battery-powered wool-rich socks promise to provide heat for up to ﬁve hours. The heating elements are in the soles and toes, and each sock takes a single D battery.

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3 OVL Flip Mirror Imaging Diagonal

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Price £59 s Supplier Optical Vision 01359 244200 s www.opticalvision.co.uk Add this ﬂip mirror to your setup in place of a regular diagonal to switch between visual observing and CCD imaging in an instant. The diagonal connects to a telescope focuser via a 1.25-inch nosepiece and has an M42x0.75 T-thread for CCD cameras.

4 Celestron FireCel Rechargeable Power Pack Price £39 s Supplier David Hinds 01525 852696 s www.celestron.uk.com The FireCel is a portable USB charger, red light torch and handwarmer all rolled into one. A useful device for observing in remote locations.

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5 Orion EZ Finder Deluxe II Reﬂex Sight Price £68 s Supplier SCS Astro 0800 018 1544 s www.scsastro.co.uk This reﬂex sight helps you aim your telescope by projecting an LED pattern onto its screen. Its dovetail ﬁnder bracket ﬁts most Orion scopes.

6 Revell Virgin Galactic Models Price £13.95 s Supplier Gizzmo Heaven 01534 861619 swww.gizzmoheaven.com Piece together the future of space tourism with this model kit of the latest Virgin Galactic craft – SpaceShipTwo and WhiteKnightTwo.

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106 EXPERT INTERVIEW MARCH

WHAT I REALLY WANT TO KNOW IS…

When is a star not a star? Sergio Dieterich is discovering where the Sun’s companions part ways with the mysterious ‘failed stars’ called brown dwarfs INTERVIEWED BY PAUL SUTHERLAND

S

tars form when interstellar gas clouds contract and condense under their own gravity. As they do so, the pressure and temperature in their cores becomes high enough for nuclear fusion to begin. Outward pressure from the heat generated by the fusion then balances the inward pressure of gravity, and the star reaches a state of equilibrium, becoming a stable object. But stars are not the only objects to form in these clouds of dust and gas. The process produces objects with masses insufﬁcient to generate the temperature and pressure necessary to ignite hydrogen. These ‘failed stars’ are known as brown dwarfs. Because they are so dim, they were not discovered until the 1990s. One of the prime missions of NASA’s WISE spacecraft was to hunt brown dwarfs using infrared light. In the local neighbourhood, it found that there is one brown dwarf for every six regular stars.

WISE revealed one ‘failed’ brown dwarf star for every six that successfully ignited

NASA/JPL, THINKSTOCK

Each end is a beginning There is a clear physical difference between these two bodies. A star generates its own energy, whereas a brown dwarf shines only at the beginning of its life due to energy produced as it condenses under gravity. A star will carry on shining as it enters what is called the ‘main sequence’ of stellar evolution, but the brown dwarf is constantly cooling. This has deep implications for the search for life. It is possible to have planets around brown dwarfs, but they tend to be poor candidates for life; brown dwarfs don’t provide a stable environment due to their rapid cooling. Knowing the cut-off point where brown dwarfs end and stars begin therefore helps us to see which bodies are more likely to host habitable worlds. I have been trying to ﬁnd out where the dividing line comes in terms of mass, temperature and radius. Using telescopes in Chile I observed 62 brown dwarfs, all very close, to measure their brightnesses and precise distances. skyatnightmagazine.com 2014

ABOUT SERGIO DIETERICH

Dr Sergio Dieterich’s research at Georgia State University in Atlanta focuses on the smallest possible stars and lowermass brown dwarfs.

It’s thought that an object must have at least seven per cent the mass of the Sun to be able to ignite and become a star. At a very young age, stars and brown dwarfs are hard to tell apart. Very cold objects, at a temperature of about 700˚C, are most certainly brown dwarfs. But objects observed in the range of about 1,200˚C to 2,200˚C could be either brown dwarfs or regular stars. The question is how small an object can you get and still have it shine like a star? It turns out that the easiest way to answer that is to look at each object’s radius. Stars are made of hot gas and so behave as we expect gas would: as they become more massive, they get bigger like a balloon. The brown dwarf operates a different way. The inside is like rubber or elastic and if you put more mass into it, it compresses itself further, so the radius would be smaller. If you put those two trends together, there should be a minimum radius-temperature relationship right at the boundary between brown dwarfs and stars. It was this minimum that we found. Brown dwarfs and other stars are no more than dots of light when seen through a telescope, so you can’t tell their size directly. But physics says that if you know the energy coming from an object and also its temperature, you can calculate its surface area. The majority of the brown dwarf’s output is in the infrared, but I also observe them in visible light too, from about 0.6μm (which is, roughly, green light) to about 20μm (mid-infrared) using WISE data. I saw that radius falls with decreasing temperature, as expected for stars, until a temperature of about 1,800˚C and a radius of around 60,500km, which is a similar size to Saturn. There we see a gap with no objects, and then the radius starts to increase with decreasing temperature, as we expect for brown dwarfs. I now want to build on my research by making sure we study all brown dwarfs within a certain distance of the Earth. S

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High in the southern evening sky lies the False Cross asterism, immersed in the star-rich region of the Milky Way between the Southern Cross (the constellation Crux) and mag –0.7 Canopus (Alpha (_) Carinae). The asterism, a group of four 2nd-magnitude stars, traditionally linked the sails and keel in the ancient constellation of Argo Navis. From the top two stars of the False Cross, a collection of a dozen 2nd- to 4th-magnitude stars clearly shows the outline of Argo’s sails, now known as the constellation of Vela.

SERP

Though the Moon is tidally locked to our planet, it regularly ‘wobbles’ on its axis, meaning we see a little more than the 50 per cent of its surface than you might expect. This phenomenon, called libration, gives us a glimpse of features that normally reside out of sight over the lunar limb, and this month there are two favourable ones. On the 8th, a libration of the northeast limb reveals craters Plutarch, Hubble and Seneca, while on the 24th a southwest limb libration unveils craters Pingre and Hausen.

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Halfway between Zeta and Gamma Leonis is an impressive edge-on spiral galaxy, NGC 3190 (RA 10h 18.1m, dec. +21° 50’), pictured. The mag. +10.9 galaxy appears elongated, 3 arcminutes by 1 arcminute, with a bright nucleus. Averted vision may reveal a dark lane running along the south side. Only 5 arcminutes northeast is mag. +11.0 elliptical galaxy NGC 3193.

OPHIUCHUS

The Sickle asterism in Leo holds two brilliant double stars. Zeta (c) Leonis (RA 10h 16.7m, dec. +23° 25’) is great in binoculars: its mag. +3.5 and mag. +6.0 stars are a wide 330 arcseconds apart – one is a paler yellow than the other. Just 3.6° above this double star is another, Gamma (a) Leonis (RA 10h 20.0m, dec. +19° 51’). Its mag. +2.4 and mag. +3.6 stars are also yellow, but separated by 4.4 arcseconds.

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