BBC Sky at Night 2017 Yearbook

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Your handbook to the best stargazing from January to December

PRACTICAL ADVICE TO GET MORE FROM YOUR KIT

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HOW TO FIND THE NEXT SUPERNOVA

TAKE BETTER ASTROPHOTOS FROM UNDER CITY SKIES

TECHNOLOGICALLYSUPERIOR

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YEARBOOK 2017

WELCOME It takes Earth 365 and a quarter days to complete one orbit of the Sun. And during that time our planet’s movements are choreographed with the other seven planets in our Solar System, the comets and meteors that orbit alongside them and galaxies that populate space beyond. This is good news for anyone with an interest in the night skies as it means that not only do we know what to look for but also where and when, which is exactly what BBC Sky at Night Magazine’s 2017 Yearbook tells you. The following 114 pages are packed with easy-to-follow instructions on how to see all the best celestial events that will be passing across the UK’s skies during the coming 12 months. But just because we know what the skies will be presenting us with doesn’t mean they don’t harbour any surprises. No matter how familiar you are with the constellations, nebulae and planets that come into view, there’s always something new to notice – especially as there are so many different ways to look for them. Whether you’re using a telescope or binoculars, a camera or filters, or just relying on your eyes alone, the skies

“No matter how familiar you are with the sky, there’s always something new to notice” always have something unexpected to reveal. And in the 2017 Yearbook you’ll also find essential tips on what equipment to use and the best ways to use it to give you the greatest chance of capturing the striking views this year’s skies have in store. Not only will the stars, planets, comets and galaxies that are on show each month keep your gaze turned upwards but we also have three longterm imaging projects to keep you busy from January to December. So here’s looking forward to an amazing year of stargazing.

Chris Bramley Editor

CREDITS EDITORIAL

PUBLISHING

Editor Chris Bramley Art Editor Steve Marsh Production Editor Rob Banino

Publisher Jemima Ransome Managing Director Andy Marshall Chairman Steven Alexander Deputy Chairman Pete Phippen CEO Tom Bureau

CONTRIBUTORS Paul Abel, Jaspal Chadha, Ian Evenden, Will Gater, Tim Jardine, Pete Lawrence, Martin Lewis, Stephen Tonkin, Mark Townley

CIRCULATION / ADVERTISING

ISTOCK

Head of Circulation Rob Brock Advertising Managers Neil Lloyd (0117 300 8276) Tony Robinson (0117 314 8811)

BBC WORLDWIDE, UK PUBLISHING

© Immediate Media Company Bristol 2016. All rights reserved. No part of Yearbook 2017 may be reproduced in any form or by any means either wholly or in part, without prior written permission of the publisher. Not to be resold, lent, hired out or otherwise disposed of by way of trade at more than the recommended retail price or in mutilated condition. Printed in the UK by William Gibbons Ltd. The publisher, editor and authors accept no responsibility in respect of any products, goods or services which may be advertised or referred to in this issue or for any errors, omissions, misstatements or mistakes in any such advertisements or references.

Director of Editorial Governance Nicholas Brett Director of Consumer Products and Publishing Andrew Moultrie Head of UK Publishing Chris Kerwin Publisher Mandy Thwaites UK Publishing Coordinator Eva Abramik

PRODUCTION

[email protected] www.bbcworldwide.com/uk--anz/ukpublishing.aspx

Production Director Sarah Powell Production Coordinator Emily Mounter Reprographics Tony Hunt and Chris Sutch

Like what you’ve read? Email us at [email protected]

YEARBOOK 2017

Contents Features Visual observing guide: supernovae Peeling back the layers Secrets of Selene Capturing planets the Dobsonian way Imaging under city skies Equipment reviews: best of 2016

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Month by month guide January February March Winter target: open cluster M35 April May June Spring target: galaxies M81 & M82 July August September Summer target: globular cluster M22 October November December Autumn target: the Crab Nebula, M1

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Features Insight Astronomy Photographer of the Year 2016 gallery Project: showing lunar libration Project: variable star light curves 3URMHFWSORWWLQJDEXWWHUƆ\GLDJUDP How to: thermally optimise your telescope +RZWRPDNHDVLPSOHVRODUƅQGHU How to: clean your DSLR sensor Subscribe to BBC Sky at Night Magazine Glossary

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YEARBOOK 2017

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VISUAL OBSERVING GUIDE SUPERNOVAE

PAUL WHITFIELD, ISTOCK X 2

Paul Abel explains how to use your telescope to hunt for exploding stars

I

n 1054 Chinese astronomers noticed the arrival of a new star in the sky. Back then, such objects were known as ‘guest stars’. Today, we know this ‘guest’ wasn’t a new star at all, but an old one

that had exploded in a cataclysmic event known as a supernova. Supernovae are among the most destructive events that nature can produce. When they happen, a single star, previously lost in the glare of the

combined light of a billion Suns, will flare up and outshine its entire galaxy. Studying supernovae not only provides important clues about star death, but also tantalising details about the expansion of the Universe > and the origins of heavy elements.

VISUAL OBSERVING GUIDE 2017 All that remains of the ‘guest star’ seen by Chinese astronomers is the Crab Nebula, M1

There’s a wonderful mystery surrounding supernovae. You never quite know when the next one will be, and when one does occur you have to be quick. You only have a small amount of time before it fades back into obscurity. Supernovae occur for two reasons: either as the final death throes of a massive star or because a white dwarf has attempted carbon burning. It is inside these cosmic fireworks that heavy elements are made, and in their afterglow, these elements are returned to the interstellar medium where they will eventually become part of new stars, planets and possibly life. Although spectacular, supernovae are rare. In our own Galaxy we would expect between one to three supernovae per century, and the last one that was visible to the naked eye occurred in 1680. Stars like Betelgeuse (Alpha Orionis), Antares (Alpha Scorpii) and Rho Cassiopeiae are all candidates. All of these stars have started their journey towards a violent death – it’s not a question of if, just when. Supernova observation falls into two categories: searching and monitoring. And as visual observers, we are well placed

many galaxies as possible, searching their elusive patchy glows for new faint pin-pricks of light. Spring is a particularly good time to start since at that time Earth is turned away from the centre of the Milky Way and facing out towards extragalactic space. Over the spring, the galaxies of Leo, Virgo and Coma Berenices are well on view.

Beginning your hunt

Betelgeuse, the red star in the shoulder of Orion, is a good candidate for going supernova

To visually hunt for supernovae, you’ll need a telescope that can see a reasonable number of galaxies, so an instrument with a 6-inch aperture at least. You’ll also need to be familiar enough with the sky that you can find them fairly quickly. Fortunately there are a number of bright galaxies out there – see the starter list on page 9 – and you should survey as many as you can in one night. You’ll need to become familiar with how these galaxies look if you are to detect any faint supernovae in the future. Making sketches is extremely helpful in this regard. Examine each galaxy at a medium power (100x, for example) and make repeat observations of it as often as possible. It has to be said that imagers have had a great deal of success here for one simple >

“You never quite know when the next supernova will be, and when one occurs you have to be quick” to make valuable contributions to this exciting field of amateur astronomy. Since supernovae are so rare, we have to search long and hard to find them. The way to do this is to examine as

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> reason: the more galaxies you can survey in a night, the better your chances of scoring a supernova. Veteran hunter Tom Boles has clocked up a staggering 155 discoveries from his observatory in Suffolk using CCD imaging. But occasionally, supernovae are discovered by accident. In January 2014 Doctor Steve Fossey of University College London was training four undergraduate students in imaging M82, the Cigar Galaxy in Ursa Major. In the process they discovered SN 2014J, a supernova that was just beginning to become visible. However you find it, if you do suspect that you’ve discovered a supernova alert Guy Hurst, the British Astronomical Association’s (BAA’s) supernova patrol coordinator at [email protected]. If a supernova is reported and it’s within the magnitude range of your telescope, you should begin observing at once. Your main goal is to make as many magnitude

SN 2014J

SN 2014J was spotted early because its discoverers were familiar enough with M82 to know it shouldn’t be there

estimates of the supernova as often as possible so that a light curve can be obtained. For this, you’ll need a star chart that has suitable comparison stars and their magnitudes listed. When SN 2014J

was reported the American Association of Variable Star Observers (AAVSO) produced an excellent comparison chart showing the location of the supernova in M82 and a number of good comparison

TYPES OF SUPERNOVAE

We can classify supernovae into two distinct types TYPE I

TYPE II

These occur in binary star systems when a white dwarf star is able to accumulate material from a nearby companion, causing the temperature of its core to start rising. If it can attract enough material, carbon fusion will start in the core. A few seconds later a runaway fusion reaction occurs and the star explodes, producing a supernova.

This type of supernova is produced when a star that is at least eight solar masses begins to collapse. Once stars of this size run out of hydrogen, they start burning other elements: first carbon, then neon, oxygen and finally silicon. Eventually the core becomes too heavy and collapses, producing a supernova.

The light curve of this type of supernova is very distinctive: there’s a peak in magnitude and then the luminosity slowly drops off. Due to the nature of the explosion, Type Ia supernovae are considered excellent ‘standard candles’ for measuring distances in space.

Type II supernovae fall into two subcategories depending on the light curves they produce. A II-L curve shows a linear falling off, while a II-P curve shows a distinctive plateau and the luminosity drops off at a much slower rate.

Luminosity

Luminosity

ISTOCK X 2, © GALAXY PICTURE LIBRARY/ALAMY, CHART BY PAUL WOOTTON, PAUL ABEL

II-P curve

II-L curve

Time

Time

THE VALUE OF LIGHT CURVES The reason we want to make as many magnitude estimates of a supernova as possible is so that the data can be plotted on a graph to produce a light curve like the ones above. Not only does the light curve

08

allow us to classify the type of supernova, with enough data professional astronomers can estimate the mass of the progenitor – and therefore determine the type of star that produced the original explosion.

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You can generate your own light curve by simply plotting your magnitudes against time in a spreadsheet. Alternatively, the BAA and AAVSO websites can do this for you if you enter your observations online.

VISUAL OBSERVING GUIDE 2017 +10.0 +10.5

SN 2014J

+11.0 +11.5 +12.0

Visual magnitude

+12.5 +13.0 +13.5

Þ The author’s rendition of SN 2014J; sketches are useful as they can reveal gradual changes

+14.0 +14.5

BAA (www.britastro.org) and the AAVSO (www.aavso.org) will be very happy to see them. Your data can be added to the growing body of observations used by professional astronomers. Despite the prevalence of digital cameras, visual observing still has a place in modern amateur astronomy. There are plenty of ways in which to make meaningful contributions: all that’s needed is a telescope, dedication and clear skies.

+15.0 15.5 16.0 11/01/14

31/01/14

20/02/14 12/03/14 01/04/14 21/04/14 11/05/14

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Date

Þ With a sharp peak and steady drop, this light curve reveals SN 2014J to be a Type Ia supernova stars to use. To estimate a supernova’s magnitude, you need to judge it against a comparison star of fixed brightness and evaluate the difference to one tenth of a magnitude. It’s best to use two comparison stars, one brighter than the variable star and one fainter. You should record your observations in the same way each session: in a log book note down the

date, time, estimated magnitude and deduced magnitude. It’s wise to draw it too, to show the supernova’s location and how it changed as it faded. For example, SN 2014J had a distinctly yellowish hue that got a little stronger as it started to diminish in brightness. Remember, your observations are of no use if they just sit on a bookshelf. Both the

START WITH THESE

GALAXIES

ABOUT THE WRITER Dr Paul Abel is an astronomer at the University of Leicester. Listen to him on our Virtual Planetarium each month.

Many galaxies worth patrolling are visible in the spring; the ones marked with an asterisk have produced supernovae in the recent past

GALAXY

LOCATION

MAGNITUDE

TYPE

APPROXIMATE DISTANCE

M81* (Bode’s)

Ursa Major

+6.9

Spiral

12 million lightyears

M82* (Cigar)

Ursa Major

+8.4

Starburst

12 million lightyears

M65

Leo

+10.3

Spiral

35 million lightyears

M66

Leo

+8.9

Spiral

36 million lightyears

M61*

Virgo Cluster

+10.2

Barred spiral

52 million lightyears

M64 (Black Eye)

Coma Berenices

+9.4

Spiral

24 million lightyears

M101* (Pinwheel)

Ursa Major

+7.9

Spiral

21 million lightyears

M51* (Whirlpool)

Canes Venatici

+8.4

Spiral

23 million lightyears

M104 (Sombrero)

Virgo

+9.0

Spiral

29 million lightyears

M84*

Virgo

+10.1

Elliptical

60 million lightyears

M85*

Coma Berenices

+10.0

Elliptical

60 million lightyears

M60*

Virgo

+9.8

Elliptical

55 million lightyears

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It’s easy for amateur astronomers to view the Sun in three remarkably different guises: (from left to right) white light, calcium K and hydrogen-alpha

PEELING BACK THE

LAYERS :LWKVXFKDZLGHYDULHW\RIWHOHVFRSHVFDPHUDVDQGƅOWHUV available, anyone can capture breathtaking images of our host star in different wavelengths, writes Mark Townley

O

bserving and imaging the Sun has never been easier or more accessible, thanks to an increasing number of solar telescopes and filter systems.

This kit isolates specific wavelengths of light coming from the Sun – white light, calcium K or hydrogen-alpha – at the same time as blocking the other wavelengths, making solar observing

safe and easy. Here we look at what these three different views will show you of the Sun’s internal structure and features, things that would be otherwise hidden by our star’s overwhelming brightness.

PEELING BACK THE LAYERS 2017

WHITE LIGHT What you can see When observing in white light you’re actually viewing a range of wavelengths across the visual spectrum. This allows you to see a layer of the Sun called the photosphere, where you can observe familiar sunspots, the darker and cooler regions where magnetic field lines are concentrated. With their darker central umbra and lighter surrounding penumbra, sunspots are the easiest feature to see. Smaller dark spots without developed umbra and penumbra are known as pores. In active regions you can observe faculae: brighter patches best seen from an oblique angle near the limb of the Sun where limb darkening allows them to stand out easier. Through larger apertures and at higher magnifications polygonal granules are visible, which are giant convective cells of plasma. Solar transits, where an object passes in front of the Sun, can also be seen. Commonly these are birds or planes, but on rare occasions the International Space Station will also pass over.

White light reveals sunspots, including their umbra and penumbra, along with brighter faculae

Imaging advice Imaging the Sun in white light is easy and a wide range of cameras can be used. With a dedicated solar filter over the front of your telescope, results can be captured and viewed instantly by holding a camera phone or compact camera afocally to the eyepiece, with a DSLR camera at prime focus or even by projecting the image of the Sun onto a white screen. The best results are achieved using a Herschel wedge and digital CCD camera, where many hundreds of individual frames are captured in video format. Using freely available software that can be downloaded from the internet, such as RegiStax or Autostakkert, the sharpest frames are automatically selected and digitally stacked into one final image which has less noise and better quality than the individual frames. This can then be coloured to individual taste using freeware such as GIMP. >

Þ A typical white light setup: a Sky-Watcher ED80 Pro apo refractor, Lunt solar wedge and a PGR Chameleon 3 camera

Any telescope can observe the Sun in white light by using a suitable front-mounted glass or solar-film filter. Be sure to get these from a dedicated astronomy retailer rather than attempting to improvise a filter yourself – the safety of your eyes is paramount. A green or continuum filter at the eyepiece end will allow a higher contrast view or image to be achieved by reducing the effects of the poor daytime seeing. For the highest contrast view, a Herschel wedge used in conjunction with a continuum filter, an ultraviolet/ infrared-cut filter and a refractor is the best option.

PETE LAWRENCE X 3, MARK TOWNLEY X 3

How to see it

Þ Autostakkert automatically selects the best frames from a

large imaging run to produce a final image of higher quality

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11

&$/&,80. At the calcium K wavelength, brighter areas known as plage can often be seen around sunspots

What you can see When you observe the Sun in calcium K light you’re viewing our star at 393 nanometres, the ultraviolet end of the spectrum. This reveals the solar chromosphere, a layer some 1,000km above the photosphere at a temperature of about 12,000 Kelvin. Most people struggle to see anything at this wavelength, so it’s better suited to imaging. Some of the features seen in white light are visible, such as sunspots with their associated umbra and penumbra, and also faculae, but now you can also see the bright white plage; areas of hot, magnetically frothy plasma that extend above the photospheric faculae. In calcium K, the influence of magnetic fields gives a bright white appearance, with the exception of the very strong magnetic fields around sunspots, which appear dark. Rarely, solar flares can be seen in calcium K and, rarer still, are darker filaments, which can be seen on the disc.

Imaging advice Calcium K imaging is a form of narrowband imaging, as only a very narrow spike of light at a certain target wavelength or colour is allowed to pass through the filter. A mono CCD or CMOS camera is the best choice for capturing images; with a colour camera, only a quarter of the Bayer matrix (the blue component in this case) that covers a colour chip would be utilised, resulting in a loss of image resolution. Freeware program FireCapture is a great choice for capturing images. Try to keep exposure times fast, as shorter calcium K wavelengths are more susceptible to poor seeing and shorter exposure times allow the moments of best seeing to be captured. Use the histogram function in the capture software to avoid overexposing the image and losing precious detail.

Þ A Lunt B1800 calcium K filter on a Sky-Watcher Evostar ED80 Pro apo refractor and Pentax Zoom eyepiece

MARK TOWNLEY X 6

How to see it

Þ FireCapture offers a wide range of intuitive and user-friendly features to make capturing images as easy as possible

12

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Observing or imaging in calcium K requires a refractor, and better results are achieved with longer focal ratio scopes as they are less susceptible to spherical aberration, which can cause a softening of the image at calcium K wavelengths, particularly in budget telescopes. A calcium K filter is needed and a number of different sizes are available from Lunt, plus a blocking filter. Be sure to check with your dealer which size of blocking filter is best suited to your telescope. If you’re observing visually, try different eyepieces from your collection as the coatings on these can affect light transmission and image brightness.

3((/,1*%$&.7+(/$<(56 2017

+<'52*(1ƨ$/3+$

The Sun is much more dynamic in hydrogen-alpha than white light; here we see a filament stretching from the sunspot group for over one million km, as well as a large prominence on the limb

What you can see Hydrogen-alpha gives the best all-round views of the Sun. It’s easy to see in the eyepiece and shows an ever-changing view of various features that never ceases to amaze: from flame-like prominences on the limb to long, snaking dark filaments that hover above the disc, both of which

are clouds of plasma held aloft by intense magnetic fields. Again you’re looking into the Sun’s chromosphere in this wavelength, albeit at a slightly different temperature and height above the photosphere than calcium K. Sunspots and the bright plage around active regions are

still visible, with solar flares noticeably brightening and then fading over a period of minutes to hours. In the best conditions a layer of spicules can be seen around the solar limb; a fine layer of dancing, hair-like jets of hot plasma that shoot out of the chromosphere.

Imaging advice As in calcium K imaging, it’s better to image with a mono CCD or CMOS camera to get the best results. Early in the morning is often the ideal time to image; before the heat of the day has built up causing the seeing conditions to blur the finer details. Always make sure you have a crisp focus by observing the limb or a high-contrast feature like a sunspot or a dark filament. Exposure times can take a while to master in hydrogen-alpha, as too much can make the prominences on the limb stand out, but at the same time can wash out disc detail. Conversely, too little exposure can give nice contrast on the disc, but then the prominences are underexposed. Capture separate images of the disc and prominences then combine them into a composite to get the best of both worlds. < Freeware ImPPG allows complete flexibility with sharpening and other post processing activities at all solar wavelengths

Þ A Sky-Watcher ED80 Pro apo refractor plus a Daystar Quark hydrogen-alpha eyepiece filter provides detailed and high-contrast views

How to see it Hydrogen-alpha offers you the largest choice of equipment. There are options to suit all budgets, from front-mounted etalon filters that fit on existing refractors or compound telescopes used in conjunction with a blocking filter, to dedicated hydrogen-alpha telescopes or rear-mounted filters that go before an eyepiece or camera. Options such as double stacking front etalon filters provide higher contrast views. The different sizes of blocking filters can seem bewildering to a novice, so it’s best to seek advice from your local astronomical society or dealer to see if you can try different options before buying.

$%2877+(:5,7(5 Mark Townley is solar astrophotographer and expert on solar telescopes, outreach and all things concerning our host star.

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Secrets of

Selene Astronomer Will Gater looks at 20 lunar targets for beginners who want to take their Moon watching further

WILL GATER X 2, CHRISTIAN FRIEBER/CCDGUIDE.COM, MICHAEL KARRER/CCDGUIDE.COM, ISTOCK

I

f you’ve just got your first telescope and are beginning to explore the night sky, there can be no better object to start your journey with than the Moon. Easy to find and brimming with hundreds of fascinating features to observe, our natural satellite ticks all the right boxes. But what if you’ve already looked at all of the most famous craters, imposing mountains ABOUT THE WRITER Will Gater is an astronomy journalist, author and astrophotographer. Follow him on Twitter: @willgater

and handful of more obvious rilles? Where do you go from here? Well, we reckon we’ve got the answer. On the following pages we’ve selected 20 lunar targets or phenomena that we think you’ll probably not have seen yet. They include intriguing volcanic features and magnificent craters, as well as several sights that you’ll need to catch at just the right time to see. Most are visible in a 6-inch scope, but a few will require a larger aperture. So read on and let us introduce you to some of the secrets of Selene.

SECRETS OF SELENE 2017

Sunrise over Copernicus T Copernicus has to be one of the most observed craters on the Moon. You’ll no doubt have already seen its spectacular terraced walls and central peak mountains. But one of the joys of lunar observing is that the illumination of any one feature changes night by night and even, much more subtly, hour by hour. The first simple challenge on this list, then, is to watch – over a few nights – the sunrise over Copernicus. Why not try a sketch to record what you see?

Changing illumination As the Moon orbits Earth we see its changing phases, with the terminator (the boundary between light and dark on the disc) moving night after night. The best time to observe most lunar features is when they’re close to the terminator and hence obliquely lit. This provides contrasting lighting and can help highlight subtle textures and topography.

T The Marius Hills We now move to the western side of the Moon, to a collection of features that you really do need the right illumination to see well. The Marius Hills are situated within the vast Oceanus Procellarum and although they’re referred to as ‘hills’, they're actually volcanic features known as domes. Through a telescope they look like pimples poking up from the smoother surrounding surface. The best time to see them is when they’re very close to the terminator around two days before full Moon.

S The Hyginus and Triesnecker rille systems Our next targets are two of the finest rille systems visible on the lunar surface. They’re a wonderful sight under steady seeing. The tentacle-like Triesnecker rille system appears to extend out from the 25km-wide Triesnecker crater, which is very close to the centre of the lunar disc, as seen from Earth. While the long Hyginus rille, a little way northeast, seems to slice right across the crater for which it is named. Look for them around a day after the first quarter Moon.

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WILL GATER X 4, MICHAEL KARRER/CCDGUIDE.COM X 2, ROBERT SCHULZ/CCDGUIDE.COM, CHRISTIAN FRIEBER/CCDGUIDE.COM

S Earthshine lit seas

W The shadows of Archimedes and its surroundings

When the Moon is a thin crescent the unlit portion of its disc is illuminated by a faint light – ‘Earthshine’ – that’s been scattered off our planet. While you may well have admired this sight with the naked eye, it’s even more breathtaking through a telescope. Use an eyepiece that fits the whole Moon within the field of view and wait until twilight has faded to a deep blue. Under these conditions you’ll see the lunar seas in shadow as well as some of the bright craters.

Moving around to the eastern edge of the Mare Imbrium we come to the Archimedes crater. You’ll likely have seen Archimedes when the Sun’s relatively high over it. But it’s worth observing it when it’s almost on the terminator. Then the crater walls cast spectacular shadows across its floor and the nearby mountains do the same onto the surrounding landscape. See if you can also spot the two peaks to Archimedes’s west throwing pointy shadows out over the sea.

W Rille near Plato Situated on the rugged northern shore of the Mare Imbrium is the beautiful crater Plato. With its smooth, dark floor it’s instantly recognisable. Your next target is not the crater itself, though, but a rille that meanders through the terrain east of it. The rille is part of Rimae Plato and you’ll need a large scope and good conditions to see it, so you may find that this is one feature you need to visit a public observatory or astronomical society to tick off.

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Steady seeing Look at the Moon with a telescope and you’ll probably notice the surface appears to gently wobble or sometimes even shimmer. This effect is caused by air movements in the atmosphere above. Such seeing conditions can vary from minute to minute and night to night, but the best views will always be had when the seeing is steady and these undulations are less intense.

SECRETS OF SELENE 2017

Craters Eddington, Russell and Struve T Some of the Moon’s most interesting features aren’t situated near the centre of the disc but in regions close to the limb. As the disc of the Moon appears to wobble during its orbit around the Earth – an effect known as libration – some of these areas become better placed for observation. Eddington, Russell and Struve are good examples of features that benefit from libration. Lunar phase and libration combine to show off these three craters best in June and July this year.

S Crater Bullialdus If you ask us, Bullialdus is one of the most underrated lunar craters. Perhaps it’s because it’s often well-lit when the more prominent Copernicus is on show. Just like Copernicus, it has an impressive undulating ejecta blanket, a striking central mountain and terraced walls. The crater is located on the western side of the Mare Nubium in the Moon’s southern hemisphere. It’s nicely illuminated around three days after the first quarter Moon when the Sun will be catching the western walls of the crater.

Rimae Hippalus X If you’ve managed to observe crater Bullialdus (above left) you may well have already spotted our next set of features. The Rimae Hippalus lie nestled among the mountains to the southwest of Bullialdus. Catch them at the right illumination – close to the terminator and with their floors just in shadow – and you can’t fail to be impressed by the three main, curved, rilles gouging their way through the lunar landscape. Like Bullialdus, they’re interestingly lit around three to four days after the first quarter Moon.

The Hortensius Domes T S Ray ejecta from crater Proclus On a night when the Moon is full there are few shadows on the lunar disc to give contrast and highlight the texture of our natural satellite’s surface. You might think therefore that it’s not worth observing the Moon then, but think again. The ray ejecta around Proclus look best when they’re illuminated from on high. The unusually shaped streaks consist of material blasted out when the crater was formed. You’ll find this bright scar near to the western edge of the Mare Crisium.

Cast your eye west of the crater Copernicus and you’ll come across a small scrap of lunar ‘sea’, known as the Mare Insularum. Close to its eastern edge is a crater called Hortensius. And just north of the crater is where you’ll find the wonderful Hortensius domes, a small cluster of volcanic domes that are a fine sight in amateur equipment. To catch these raised bumps on the lunar surface at their optimum illumination look for them on about nine days after new Moon.

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W Crater Pythagoras and its central mountains Eratosthenes and Copernicus are good examples of craters with central mountains, formed when the lunar surface rebounded in response to the impact that made the crater. Because of their position on the lunar disc, though, our view of these craters’ mountains is from almost directly above. Crater Pythagoras, on the other hand, is very close to the northwest limb of the Moon and so we see its central mountains at an oblique angle, providing the spectacular sight of the peaks rising out of the crater floor.

T Rima Ariadaeus There are many rilles on the Moon but few are as striking as Rima Ariadaeus. This fault in the lunar surface stretches roughly 250km from one end to the other. A small telescope should show it well – you’ll find it cutting through the rough terrain between the craters Julius Caesar and Agrippa. Like all lunar rilles, Rima Ariadaeus’s appearance alters dramatically with the Moon’s changing phase; for a good view of the rille, seek it out on nights around first quarter Moon.

S Craters Atlas and Hercules

WILL GATER X 5, MICHAEL KARRER/CCDGUIDE.COM X 2, OLIVER SCHNEIDER/CCDGUIDE.COM, ROBERT SCHULZ/CCDGUIDE.COM

Atlas and Hercules are two truly exceptional craters in the northeastern part of the Moon’s disc. Hercules is about 70km across and appears to have a relatively smooth floor that contains the pockmark of another crater: Hercules G. Atlas meanwhile is somewhat larger, about 87km wide, and you may be able to spot the rilles on its floor with a large aperture telescope under the right lighting conditions. Look for them both when the Moon is a crescent, around five days after the new Moon.

T Mons Rümker The Oceanus Procellarum is littered with intriguing selenological features and Mons Rümker is one them. It’s a wide, relatively flat, volcanic peak that rises out of the smooth basalt plains in the far north of Oceanus Procellarum. It’s situated close to the limb of the Moon, west of the famous Bay of Rainbows, Sinus Iridum. Ideally you want to observe it six days after the first quarter Moon, when the angle of the Sun casts shadows that show it off best.

W Wrinkle ridges in Oceanus Procellarum and Mare Imbrium While we’re exploring the northwest sector of the Moon let’s concentrate on some other, subtler, features in this region. Wrinkle ridges are perfectly named – through a telescope they appear like giant creases in the smooth lunar seas. It’s thought they were formed when the Moon’s surface contracted. There are many wonderful examples in the Oceanus Procellarum and the nearby Mare Imbrium. You’ll find one of the finest southeast of the western tip of the Sinus Iridum – look for it around 10 days after new Moon.

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SECRETS OF SELENE 2017

W Reiner Gamma When it comes to intriguing lunar features, they don’t come much more intriguing than the enigmatic Reiner Gamma. This bright marking in the Oceanus Procellarum resembles a tadpole with a long, wriggling tail. A 2015 study suggests it might be the result of a comet smashing into the Moon. It’s located about halfway between the craters Marius and Cavalerius. To see it you’ll need to observe it six to seven days after the first quarter Moon, when it's not washed out too much by direct illumination.

T Kies Pi W Wrinkle ridges in Mare Fecunditatis If you enjoyed observing the wrinkle ridges in the Oceanus Procellarum and the Mare Imbrium, both mentioned earlier, it’s worth turning your attention to the Mare Fecunditatis roughly two days after new Moon. Here there are some particularly beautiful wrinkle ridges that wind their way across large parts of the lunar sea. If you have clear skies for a number of nights, you can watch day by day as the changing illumination causes the ridges to seemingly dissolve from view.

No discussion of the secret treasures of the Moon’s surface would be complete without a mention of the lunar dome Kies Pi. You’ll find this fascinating volcanic feature – essentially a lunar shield volcano – very close to the crater Kies in the Mare Nubium. Through a telescope it appears to resemble a raised blister in the smooth surface around it. Since it’s such a subtle feature, you do need steady seeing conditions to see it well. It’s particularly well illuminated roughly four days before the full Moon.

5IOVQÅKI\QWV UIOQK S Rimae Janssen The 20th feature in our list takes us south to crater Janssen. This 200km-wide depression sits among the mass of craters in the Moon’s south-eastern sector. Janssen can be tricky to make out under some illuminations as, despite being relatively large, there are several smaller craters that break up its outline. It’s the rille that arcs across Janssen’s floor that we’re most interested in here though. You’ll need a large scope to see it clearly – look for it about five days after new Moon.

To change the magnification of a telescope setup – and thus get either a ‘closer’ or wider view – you need to use different eyepieces; the shorter the focal length of the eyepiece the more magnification you’ll get. But remember, it’s easy to push the magnification too far, so try to match the eyepiece you use to the seeing conditions and capabilities of your scope.

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CAPTURING

PLANETS

THE DOBSONIAN WAY

Dobsonian scopes can be adapted for effective planetary imaging – Martin Lewis explains how

Jupiter, Mars, Saturn and Venus imaged through the author’s Dobsonian scopes

CAPTURING PLANETS THE DOBSONIAN WAY 2017

D

obsonian-mounted Newtonian telescopes are very popular due to their ease of use and value for money – they give the largest aperture possible for the lowest cost. The Newtonian design is simple. Being a pure reflector there are no issues with colour fringing and the central obstruction also tends to be smaller than in other reflectors, such as Schmidt-Cassegrains. This means that large-aperture and lowcost Dobsonians can often yield great planetary images. Their big aperture makes the images bright and contrasted, and provides extra resolving power to see surface detail. The Dobsonian mount was intended to be a simple push-to altaz mount for visual observing, and by far and away the majority of Dobsonian telescopes are operated like this. However, some astronomers have found ways of using their Dobsonian reflectors to take great photos of the planets by recording video and then stacking individual frames using software such as RegiStax or Autostakkert!, reducing the blurring effects of the atmosphere. Sharpened in a graphics editor, the final image shows a wealth of surface detail.

Þ The gas giant Jupiter imaged with a 8.7-inch Dobsonian using the drift method

Drift or driven

X Venus: no real limit over one session X Mars: five minutes X Jupiter: five minutes X Saturn: 10 minutes

Þ Jupiter imaged with the same scope but mounted on a driven equatorial platform

You’ll probably need to use a Barlow lens to enlarge the planet’s image, and the best magnification Barlow depends upon a number of factors. Too low and you’ll lose detail by undersampling, but if it’s too high you’ll have to manually reposition your telescope frequently. Start with a power that gives a focal ratio of f/10 and

experiment around there. If you can, use a camera with a bigger chip to maximise the percentage of time that the planet is in the frame. Although you can get reasonably pleasing photos with the drift method, driven methods really let you pull out significant planetary detail. With a driven

scope you eliminate drift smearing and can increase the magnification to boost the image scale without worrying about getting very short drift runs. Also, you can gather more frames to help reduce image noise because you don’t need to waste time repeatedly moving your telescope to the start of the drift run. >

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MARTIN LEWIS X 6, WWW.THESECRETSTUDIO.NET

The simplest way of capturing videos is the drift method, which requires no driven mount. Just capture multiple short video sequences as the planet drifts through the field and then combine the videos into one image. Each second a planet drifts about 15 arcseconds, so exposures of 30 milliseconds will lead to drift smearing of only about 0.5 arcseconds, similar to the level of detail you would see on a good night. The true window over which you can gather videos is also limited by rotational smearing. The following list lets you know how long you can image the planets before rotational smearing of about 1 arcsecond becomes evident:

> But if Dobsonians are supposed to be

push-to scopes, how do you get them to track a planet? One method is to fit a Go-To drive system and the other is to place the scope on an equatorial platform. Neither of these methods would probably be good enough for long-exposure deepsky photos, but because planetary images are generally a few tens of milliseconds long, and because of the frame-to-frame alignment capability of the stacking programs, both types are good enough for planetary imaging. Go-Tos generally use friction drives on the altitude and azimuth axes, which

can be engaged or disengaged to change between ‘go-to’ and ‘push-to’. Equipped like this, a Dobsonian should be able to keep the planet in frame and allow you to record videos to process into detailed pictures later. The Go-To will make finding your target easy and you should be able to compensate for any inaccuracies by using the motors manually to recentre the planet. Because you’re using an altaz system, however, in time the planet will rotate relative to the frame of the camera. This is less of a problem for planets than for deep-sky imaging because the videos tend to just be a few minutes long, limiting

the amount of rotation during a video. Over the course of 10 or 20 minutes, however, the field rotation could become noticeable if you’re combining images from different videos. Fortunately the useful derotate function in WinJupos (jupos.org/gh/download.htm) will not only compensate for the rotation of the planet on its axis, but also for orientational drift due to this field rotation effect.

The equatorial approach Mounting your Dobsonian on an equatorial platform is your second option and gives your scope true equatorial

How to capture images with

the drift method

Step 1

Step 2

Step 3

Step 4

Set up your scope and allow it to cool to reduce thermal currents, then collimate as normal. Connect a digital video camera to the telescope and, looking at your laptop, focus critically on a star. Polaris is a good choice for the star as it won’t move while you are focusing.

Reposition the scope so the finder cross hairs are just ahead of the planet. As soon as the planet enters the camera frame, hit record. Keep recording until the planet drifts out of the frame. Quickly repeat. Keep going until you’ve gone outside the time window for your target.

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Line up your finderscope so that Polaris is near the middle of the camera frame. Align on the planet and check the chosen exposure settings. Planet brightness should be about 70-80 per cent of the saturation level and the gain about 50-75 per cent of maximum.

Join your videos together using PIPP’s (sites.google.com/site/ astropipp) ‘Join’ mode. Use the ‘Object Detection’ and ‘Centre and Crop’ functions to keep the planet centred and eliminate the empty frames. Process this output video in RegiStax or Autostakkert! to finish.

CAPTURING PLANETS THE DOBSONIAN WAY 2017

Equatorial platforms How this setup tracks like a German-equatorial mount Understanding how an equatorial platform works can be confusing – they look so different from most other types of equatorial mount and don’t seem to have an obvious rotation axis. To help with understanding imagine this:

movement for an hour or so before the platform needs to be repositioned back to the start. Like the Go-To drive method, it maintains the low, stable centre of gravity of the Dobsonian design. With it you can continue to use the normal push-to altaz movements of the Dobsonian mount that are so much more in tune with the human frame of reference, but as soon as you’ve found the target it stays put in field as the equatorial platform tracks it. An equatorial platform can be moved between scopes and even used to place a normal camera tripod on to turn your DSLR into a fully tracked camera. Commercial equatorial platforms are available from a number of different suppliers and are generally made for a specific latitude. For planetary imaging, absolute tracking accuracy from the drive system is not essential but it is useful to be able to adjust the drive speed slightly to keep the target in the field. Some platforms also have a screw jack on the southern end to help move the object up and down in the field. One of the most important characteristics of a telescope drive system, if you want the highest resolution images, is that vibration

Solid cone resting on ground with centre axis pointing at north celestial pole

N Pairs of bracket-mounted roller bearings, set at an angle each side of cone to allow it to rotate about its centre axis

Single, driven roller bearing makes cone rotate at same speed as stars (sidereal rate)

Cutting through cone parallel with ground and removing top section leaves a level platform with equatorial motion

should have an insignificant effect on the image. Equatorial platforms are prone to such vibration as they often use stepper motors as the main drive. You may not see signs of this vibration in normal use at the eyepiece but if it’s there it will prevent you from achieving full highresolution imaging. You can check for vibration by inserting a high-power eyepiece and checking the smoothness of the twisted track of a bright

star when you firmly tap the eyepiece to shake the scope. Vibration will be seen as a sawtooth on the smooth path.

Þ A tapped eyepiece at high power; the star path is smooth as it settles down again

Pole star

ABOUT THE WRITER Martin Lewis is a keen astronomer. He has in-depth knowledge of observing with all sorts of equipment.

MARTIN LEWIS X 7

The author’s home-built 8.7-inch Dobsonian on a home-built equatorial mount

X There is a large solid cone on the ground with its centre axis pointing at the North Celestial Pole. X Two pairs of roller bearings are fitted on brackets running against the outside surface of the cone, one pair near the narrow end and the other pair near

the wide end, angled so their axes point towards the apex of the cone. These should restrict the cone to rotating about its axis. X One roller is driven so the cone rotates to follow the stars. X Cut through the cone parallel with the ground and dispose of the top section. The flat platform that’s left will have equatorial tracking properties. X Anything placed on this platform will automatically follow the stars as it will have an axis pointing at the Pole Star and be rotating at the same rate as the night sky.

Þ If the star path shows a sawtooth pattern, it indicates that drive vibration is present WWW.SKYATNIGHTMAGAZINE.COM

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IMAGING UNDER

CITY SKIES Jaspal Chadha reveals how you can capture quality deep-sky images under light-polluted skies

F

or the last few years I’ve been taking images of the night skies. But there’s a problem: I live in London, one of the most light-polluted areas in the UK. This makes it hard to achieve one of the main requirements for a good astro image – a high signal to noise ratio. While the best way to increase that ratio is to reduce the noise by imaging from a site with darker skies, there are various things you can do to capture decent images from under the urban lights in the middle of a city. After months of trial and error I finally settled upon a setup that works for me. When I started I used a DSLR and colour single shot CCD. The results weren’t what I expected. The images lacked detail and were often filled with the orange glow of light pollution, despite my best attempts to reduce it. Even with exposures of four hours I wasn’t happy with the amount of detail being captured and trying to remove the glow with photo-editing software was a long process that still didn’t get me the results I wanted.

Sacrifice colour for clarity Things improved when I switched to using a monochrome CCD camera, an option that retains the main advantage of a CCD: its sensitivity. The more sensitive the camera, the shorter the exposure

If you live in the city, the full Moon is far from the only source of irritating sky glare – but it’s possible to capture wonderful images all the same

required to detect faint detail. CCD cameras have a greater dynamic range than DSLR cameras, meaning there’s a larger range of luminosity that they can detect. The CCD can more easily capture both faint and bright detail in a single exposure, rather than needing several images to bring out different elements. However, a mono CCD only detects the brightness of the light, not its colour. If you want to bring out the colour of images you have to use filters. In normal colour imaging, three filters are used to separate the primary colours of the visual spectrum. Red, green and blue (RGB) filters are designed to approximate the colour sensitivity of the human eye, so that the resulting image is true colour. When using RGB filters to create a broadband image, all types of wavelengths are captured across the entire visible spectrum so this picks up a lot of light pollution from the surrounding

“My images lacked detail DQGZHUHRIWHQƅOOHGZLWK WKHRUDQJHJORZRI OLJKWSROOXWLRQŠ

IMAGING UNDER CITY SKIES 2017 city lights. This is usually most visible as green and magenta gradients in the images. To reduce this I use a simple CLS CCD light-pollution filter. There are a few things to remember when using light-pollution filters, however. First is that they’re not 100 per cent foolproof when it comes to light suppression. These filters are helpful, but they have their drawbacks. All of them are designed to block out only particular wavelengths of light and there’s one overriding factor to consider when deciding how effective they’ll be for you. They’re designed to block the wavelengths emitted by low-pressure sodium-vapour lamps – the orange type. If the location where you make your observations from is lit by newer LED street lamps, then light-pollution filters will be useless. They also cut down the total light getting to the sensor, so the exposures required will be longer. But they should increase the ratio of useful image information compared to background glow, so overall should result in an improvement.

Jaspal’s setup: switching to a mono CCD has made all the difference under the light-polluted London skies

Go deeper by narrowing down

Much time and effort will be required to capture data from all three filters. So little light gets past the filter that imaging requires very long exposure times. Typically I’ll spend at least three to four hours’ imaging time on each filter, with some single exposures of up to an hour. The most rewarding results come from the Ha filter. The image is readily visible and has much detail. The OIII and SII filters produce dim, noisy images that are frustrating to work with, but are needed for a complete image.

Staying on target Keeping the telescope on track when narrowband imaging takes some practice too. I use an autoguider, and finding a stable guide star can be a challenge thanks to the fact that so little light reaches the >

© PAUL CARSTAIRS/ALAMY STOCK PHOTO, JASPAL CHADHA X 3

For those times when I want to bring out the finer detail of a deep-sky object, I attach narrowband filters: the light-pollution filter’s green tint is easy to remove in photo-editing software during the image-processing stage. These filters enhance the contrast of emission objects by accepting only a narrow range of wavelengths around the emission lines of certain gasses within the objects, such as hydrogen-alpha (Ha), doubly ionised oxygen (OIII), ionised sulphur (SII) and others. During the image-processing stage, data from each emission line is assigned a certain colour band – red, green or blue – and these are combined later in a graphics editor to create the most stunning images. As narrowband filters only pick up a tiny portion of the available light, they can be used to take astrophotos even when the Moon is up as well or from locations that are usually plagued by light pollution. Narrowband filters commonly come with a bandwidth of 5nm or 3nm at the emission line they let through; you can expect to pay a higher price for the lower bandwidth filters.

Þ The night sky before (left) and after (right) processing – the amount of sky glow that can be removed with editing software is tremendous WWW.SKYATNIGHTMAGAZINE.COM

25

> guide camera’s sensor. Some narrowband imagers choose to use a separate camera on a guidescope. This has several advantages, the biggest being that since the guide CCD is not looking through the narrowband filter, the stars appear considerably brighter and finding a suitable guide star is easy. The drawback to a guidescope though is flexure, where different parts of the telescope setup move by different amounts over the course of the night. This means that the main telescope may not be perfectly aligned with the guidescope during the course of the exposure. I use an off-axis guider that allows you to guide your telescope through the same optics that are taking the picture. This eliminates any possibility of guiding error. However, the main difference between narrowband and broadband images comes when you combine the colours for the first time using image-editing software. Generally I use the standard Hubble palette combination where SII is red, Ha is green and OIII is blue. Since the Ha is usually a much stronger emission line, the result comes out very green. So it’s a good idea to assign the SII and OIII a stronger combine factor, or do an equivalent in Photoshop to ‘push’ the SII and OIII data before combining them. Even when that is done, it’s likely you’ll want to do more colour adjustments, such as

Þ Planetarium programs like Stellarium can help you to plan your sessions

Forward planning 1. Plan your imaging in advance using a planetarium program such as Stellarium (www.stellarium.org) to work out where your target is going to be in the sky and how much time you have to capture it. This will also help you work out where the best place in your garden or observing site will be to both avoid light pollution and get the best view.

2. Image when your desired object is just past the meridian line in the sky. This will ensure you have the best sky conditions and will help shy away from light pollution. 3. Invest in a decent mount that will allow you to track for a longer period if you’re aiming to do long-exposure astrophotography.

Mixing SII, Ha and OIII data in the RGB channels respectively can be used to give images reminiscent of the Hubble Space Telescope – this one is of the Heart Nebula

JASPAL CHADHA X 10, WWW.STELLARIUM.ORG

Another Hubble palette rendition, this time of open cluster Melotte 15 within the Heart Nebula

Variants on the Hubble palette can be achieved by giving extra weighting to the SII and OIII channels, as seen in this shot of the Wizard Nebula

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IMAGING UNDER CITY SKIES 2017 1

2

3

Þ The Bubble Nebula: OIII (1) and SII (2) filters produce dim and noisy images, but when combined with Ha data the result (3) is great adding a Selective Colour adjustment layer, before the results become pleasing. Though I try to cut down on light pollution, there’s always a little that gets through. To cope with this, I use a powerful program called Gradient Xterminator (www.rc-astro.com/resources/ GradientXTerminator) when processing data. This Photoshop plug-in destroys light wash and amplifier glow from surrounding lights that may have been introduced while imaging. Eventually, once all of this is done I arrive at my final image. It might take a bit of work, but you’d be amazed with what you can accomplish even under the skies of a city.

ABOUT THE WRITER Jaspal Chadha has been an astro-imaging enthusiast for two and a half years. Observing from London, he has to overcome heavily polluted skies.

Þ Even from a polluted sky it’s possible to capture great deep-sky shots; clockwise from above: the Whirlpool Galaxy, the Dumbbell Nebula and globular cluster M13

Reducing light pollution Hiding away from light pollution is much more effective than editing it out afterwards Shielding your equipment from stray light can be as simple as adding a cardboard cuff to the end of your scope, or by extending the dew shield. A lot of stray or unwanted light comes from security lights. If you have them, turn them off while you’re observing. If your neighbour’s security lights are troublesome, politely ask if they can be turned off during your observing sessions. An offer to show the neighbours what you’re looking at can work wonders and you never know, you might convert them to your hobby. Stray light gradually decreases as the night goes on. More people head to bed, turning off the lights in their homes as they go, and some local authorities turn street lighting down or off after midnight. If you’re able to stay out late, you’ll probably find that after midnight the amount of stray

light around seems to be less than earlier in the evening. Even if you have streetlights shining into your garden, it’s usually possible to find a spot that’s not illuminated by them, giving a good view of the sky. Getting into the shadow of a brick wall or a tree can help here, though this can block your view of a large part of the sky, so you may need to hunt around for the best spot in your garden. One of the most difficult forms of light pollution comes from artificial light being shone directly into the sky and reflecting back off dust and water vapour, filling the night with a haze of light. High humidity or prolonged dry spells when dust can be thrown up into the atmosphere will seem to make the situation worse. Check weather reports and wait for stable conditions with low wind speeds to get the darkest skies.

Þ Jaspal’s observatory is at the back of his garden, where trees help to shield it from light pollution

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EQUIPMENT REVIEWS BEST OF 2016

EQUIPMENT REVIEWS

BEST OF 2016

NICK ALTAIR/WWW.ALTAIRASTRO.COM, WWW.THESECRETSTUDIO.NET

Some of WKHƅQHVW DVWURQRPLFDO HTXLSPHQWWR SDVVWKURXJK RXUWHVWLQJODEV LQWKHSDVW\HDU

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EQUIPMENT REVIEWS BEST OF 2016

PrimaLuceLab AIRY APO120 refractor A surprising scope with a doublet that offers astounding and aberration-free views Rotatable assembly

On-axis locking accessory holder Instead of the usual thumbscrews to attach a diagonal or camera equipment to the optical tube, there’s a simple clamp that locks and loosens with a single twist. The inner rings of the clamp apply even and firm pressure to accessories, holding them centrally.

The focuser assembly can be rotated or the eyepiece/camera alone can be rotated. This allows for accurate framing of photographic targets and helps you find the most comfortable viewing and focusing position on a variety of mounts.

Focuser PrimaLuceLab calls this a Hybrid-Drive focuser. The well-engineered mechanism is smooth like a Crayford, yet strong and non-flexing, with rack and pinion-style gearing. Precise focus adjustments are easily managed with the dual-speed action, which firmly locks in place.

User manual Bucking the trend for online-only manuals, there’s a detailed user guide with useful photographic diagrams to help with setting up the telescope for visual or photographic use, and a complete list of available accessories for the AIRY APO120.

ALL PICTURES: WWW.THESECRETSTUDIO.NET

P

rimaLuceLab’s AIRY APO120 refractor arrived on one of the few days of 2016’s summer when the weather, Moon and short nights decided to play nicely together. The first target we observed with it was Jupiter, using our own premium 10mm eyepiece and a 2x Barlow lens. The view was remarkable. The equatorial bands were crisp and sharp, the Great Red Spot stood out clearly and there wasn’t a trace of colour fringing or chromatic aberration. Jupiter looked superb, like a photograph. After putting the accurate colour correction to good use by viewing some more vibrant stars – Albireo in Cygnus, Arcturus in Boötes and Mirach in Andromeda – we turned our sights on Mars and Saturn, again with a Barlow lens

30

Carry case The rigid and lockable padded case makes a useful accessory, ideal for transporting or safely storing the telescope when it’s not in use. The aluminium case is 90x30x29cm and weighs only 4.3kg. There are handles on the top and ends of the case.

to increase magnification. Mars was a clear disc with good contrast on the darker regions and the typical dusky pink surface, while Saturn displayed the Cassini Division within its rings and well-defined coloured banding, all without interference from colour halos. The AIRY APO120 comes in a nice case, with matching tube rings, end cap, focuser and eyepiece holder, full instructions and a four-year warranty. The dew shield extends smoothly without tilting or slipping, and the twist and lock eyepiece holder rounds off a great package. Of course, all of this comes at a price, and the AIRY APO120 is at the premium end of the market. However the combination of almost-perfect views, with a respectable 4.72-inch aperture and a useful 900mm of

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focal length, in a telescope weighing just 8kg, could place the AIRY APO120 on the radar of astronomers looking for their next or final upgrade.

VITAL STATISTICS • Price £2,497 • Optics Multicoated apochromatic doublet • Aperture 120mm (4.72 inches) • Focal length 900mm (f/7.5) • Focuser Dual speed 1:11 Hybrid-Drive • Extras Tube rings, end cap, carry case • Weight 8.0kg • Supplier 365 Astronomy • www.365astronomy.com • Tel 020 3384 5187

VERDICT

+++++

EQUIPMENT REVIEWS BEST OF 2016

'D\VWDU4XDUNFDOFLXP+H\HSLHFHƅOWHU You’ve seen the Sun in white light and hydrogen-alpha red; now see it in purple

D

Ports The filter accepts power through a female micro-B USB connector. This means you can also power it using an external battery – giving you complete portability – so long as the battery can deliver the 1.5-amp current needed to heat the etalon chamber.

Tuning knob The tuning knob adjusts the centre wavelength of the filter, allowing you to tweak it to get better views of redshifted or blueshifted material moving towards or away from the Sun. This also allows compensation for any focuser sag present in the telescope.

Nosepieces The nosepieces thread onto the filter body, so it can be used in a range of star diagonals or directly in the focuser to extend or shorten the amount of back focus. This ensures maximum compatibility with various refractors.

Power The supplied 90-240V adaptor includes UK, US, Euro and Australian plugs, which along with the Quark calcium-H’s compact size makes it ideal for foreign travel. The 1.5m cable is ample length to connect when the Quark is mounted on a telescope.

aystar’s Quark hydrogen-alpha eyepiece filter was a popular item and quickly gained a following after its launch in 2014. Not long after that amateurs began asking for a calcium version. And here is the Quark calcium-H. As the calcium-H wavelength is 396.85nm, in the violet region of the spectrum, the views of the solar chromosphere it delivers are quite different to what you might expect through a hydrogen-alpha filter. The Quark calcium-H is designed to be used with refractors with a focal ratio of f/7 or greater and, as with any form of solar observing, precautions must be taken. We used the filter with a 100mm f10 Tal100R refractor, placing it in the diagonal with the energy reflection filter. Using a 15mm Plössl eyepiece gave us a rich, well contrasted view of the full solar disc and it was easy to see the brighter areas of plage and faculae set against the violet background. Darker sunspots with their umbra and penumbra could also be seen within the active regions. It was interesting to note that the brightness and quality of view was eyepiece dependent; this is due to their anti-reflective coatings and designs, rather than the Quark filter. It’s therefore worth experimenting with various eyepieces to see which one offers you the best performance. The simplicity and ease of use of the Quark calcium-H make it suitable both for seasoned solar observers wanting to see our star in a new light and beginners. Given how easy it is to image and observe with this eyepiece filter, Daystar may well have a game changer on its hands.

VITAL STATISTICS

Case The supplied plastic bolt case provides a robust and sturdy means of storage. Daystar says keeping the Quark calcium-H in a dry, climate-controlled environment when not in use can extend the lifespan of the filter two or three times.

• Price £999 • Tuning range 5 Angström FWHM (+/– 0.5 Angströmin 0.1 Angström increments) • Power requirements 5V 1.5 amp • Extras 1.25-inch and 2-inch nosepieces, 1.25-inch extension tube, 240V power supply, storage case • Weight 200g • Supplier Altair Astro • www.altairastro.com • Tel 01263 731505

VERDICT

+++++

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31

EQUIPMENT REVIEWS BEST OF 2016

SkyVision 24-inch T600 Compact Go-To Dobsonian A mighty truss Dobsonian with a colossal aperture and smooth tracking Focuser The choice of focuser is one of the decisions to be made at time of purchase, but the default option is a Starlight Feather Touch with normal and slow speed knobs. The beautiful engineering on this focuser complements that of the rest of the telescope.

Truss poles The carbon fibre truss poles are works of art in themselves and exemplify the attention to detail present throughout the instrument. Each is 27mm in diameter and they link together in a single expandable set, which readily locks into position with quick-release levers.

Thermal management The large mirror contains a lot of glass, so to help it acclimatise to night-time temperatures there are two 100mm fans in the side of the mirror box. These blow ambient air onto the side and underside of the mirror to cool it down.

Optics The 24-inch primary mirror is made of low-expansion Suprax glass and possesses high-reflectivity coatings. The mirror sits on an 18-point support cell and is beautifully finished with no visible streaks plus a perfectly ground edge bevel. The telescope has a short focal ratio of f/3.3 to keep the eyepiece height low.

I

f you want the finest deep-sky views, you need large, photon-grabbing optics of a high quality. The SkyVision T600 Compact Dobsonian with its whopping 24-inch diameter mirror provides them. Even a cursory look at this telescope shows its an elegant piece of engineering. It can be disassembled into manageable parts that fit into a car, has full Go-To capability and motorised tracking to further enhance your observing. The first object we viewed with it was the Ring Nebula, high overhead, which was big and bright in the 6mm eyepiece. Using the same eyepiece we turned to M13 and M15, two of the finest globular clusters in the sky, which were easily resolved to their cores. Another memorable view was the Dumbbell Nebula, which we glimpsed through a binoviewer and a pair of 24mm Panoptic eyepieces. The nebula had a mesmerising 3D appearance and was truly wonderful. With this setup we moved on to the Blue Snowball planetary nebula and were able to clearly see the inner structure even at this low magnification. We followed our deep-sky viewing with some star testing, which showed smooth optics but signs of minor overcorrection – this may have disappeared with further cooling of the primary mirror. The secondary mirror is quite exposed at the top of the secondary cage, and dewed up during our observing session so we had to warm it up using the mirror’s 12V rear heater. A lightweight extension to the top of the secondary cage might have delayed such dewing and if fitted opposite the eyepiece would have blocked extraneous light reaching the eyepiece from the sky behind the secondary mirror. All in all the SkyVision T600 is an advanced scope for serious visual observers. It delivers great performance in a beautifully crafted instrument that’s a joy to look at and a pleasure to use.

Bearings The azimuth bearings are PTFE pads riding on an FRP glass board, a standard combination for many largeaperture Dobsonians. The altitude bearings are quite different and are special rollers with a friction preload originally designed for CNC machine tools.

32

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• Price Contact Altair Astro • Aperture 600mm (24 inches) • Focal length 1,980mm (f/3.3) • Focuser Starlight Feather Touch • Go-To system StellarCAT and Sky Commander user interface • Weight 99kg • Supplier Altair Astro • www.altairastro.com • Tel 01263 731505

VERDICT

+++++

ALL PICTURES: NICK ALTAIR/WWW.ALTAIRASTRO.COM

VITAL STATISTICS

SINCE

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In Back Garden Astronomy, we’re aiming to make the night sky a little bit less bewildering. Within, you’ll find everything you need to know for your first night under the stars and beyond. We start with essential knowledge all astronomers need to know – such as why the sky moves and how celestial coordinates work – followed by sections on the equipment you’ll need to get going and what you can expect to see. Your astronomical adventure starts here. Plus – subscribers to BBC Sky at Night Magazine receive FREE UK P&P

Learn the basics of observational astronomy We talk you through all the major celestial and the practical advice you need for a sights waiting for you and provide tested successful first night under the stars observing advice on how to see them

Get to grips with the vast range of astronomical equipment, and find out which setup best suits your needs

ORDER YOUR COPY TODAY www.buysubscriptions.com/backgarden Alternatively call 0844 844 0254 and quote ‘BACKHA17’ †

†Calls will cost 7p per minute plus your telephone company’s access charge. Lines are open 8am-8pm weekdays & 9am-1pm Saturday. *Subscribers to BBC Sky at Night Magazine receive FREE UK POSTAGE on this special edition. Prices including postage are: £11.49 for all other UK residents, £12.99 for Europe and £13.49 for Rest of World. Please allow up to 28 days for delivery.

MONTH BY MONTH GUIDE 2017

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Month by month

GUIDE What to see in the night sky throughout the year

by Pete Lawrence

January

May . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

September

Meteor showers and comets get the year off to a dazzling start

Shorter nights mean you have to pack more into less time

The September skies play host to some lovely close approaches

February

June

..................

36

40

.............................

58

October

.............

....................

72

78

There’s a long list of sights to see in the year’s shortest month

Dawn and dusk display the effects left by meteors on Earth’s sky

The Orionid meteor shower lights up the late-October sky

March . . . . . . . . . . . . . . . . . . . . . . . . . . 44

July . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

November

See distant galaxies with the Milky Way out of view

The Milky Way makes its presence felt as the month progresses

Witness a nice close conjunction and a grand lunar occultation

August

December

April ISTOCK

....................

.............................

50

X marks the spot on the Moon and Lyra is the radiant for meteors

.......................

68

Two eclipses make August a busy month for our Moon

...............

...............

82

86

The Moon moves aside for the Geminid meteor shower this month

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JANUARY 2017

OUR SUN WINNER & OVERALL WINNER

Baily’s Beads Yu Jun, China

36

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JANUARY 2017

JANUARY

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KEY DATES 2 JANUARY Venus, the crescent Moon and Mars form a straight line in the evening sky

3 JANUARY Peak of the annual Quadrantid meteor shower

5 JANUARY Seventh magnitude comet 45P/Honda-Mrkos-Pajdusakova close to Theta (e) Capricorni

18 JANUARY Asteroid Vesta reaches opposition at mag. +6.1 in Cancer

22 JANUARY Galilean moon Callisto appears just south of Jupiter at 06:15 UT

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LAST QUARTER MOON 19 Jan

CONSTELLATION NAME GALAXY

MOON PHASES Key stages in the monthly cycle FULL MOON 12 Jan

STAR NAME

GLOBULAR CLUSTER PLANETARY NEBULA DIFFUSE NEBULOSITY DOUBLE STAR

VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

MARS

JUPITER

SATURN

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NEPTUNE

A bright evening object that reaches greatest eastern elongation, 47.1° from the Sun, on 12 Jan

An evening planet in Aquarius, appears 20 arcminutes from Neptune on 1 Jan

A morning planet in Virgo with the Moon nearby on the morning of 19 Jan

A morning planet in Ophiuchus with the Moon nearby on the morning of 24 Jan

An evening planet in Pisces best seen at the start of Jan around 18:30 UT

An evening planet that has an apparent close encounter with Mars on 1 Jan and Venus on 12 Jan

STAR-HOPPING PATH METEOR RADIANT et

VENUS

Well placed in the morning sky, reaches greatest western elongation of 24.1° on 19 Jan

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PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

38

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MAG. 0 MAG. +1 MAG. +2 MAG. +3 MAG. +4 & BRIGHTER & FAINTER

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JANUARY 2017

JANUARY at a glance Meteor showers and comets get the year off to a dazzling start Comet 45P/Honda-MrkosPajdusakova traces a path across our sky early in the year

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Comet positions correct for 00:00 UT on the dates shown 1-14 Jan – Evening object, low in the southwest 15-31 Jan – Lost from view 1 Feb – Morning object

SAGITTARIUS CAPRICORNUS Antares

SCORPIUS

star Rigel in the southwest corner and bright orange Betelgeuse in the northeast corner. Extend a line from Rigel through Betelgeuse for almost twice that distance again to arrive at a pair of similar brightness stars known as Castor and Pollux, the two main stars of Gemini. Look closer and you’ll see that Castor is Lunar phase Plough

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3 Jan 28% wa xing crescent Sets at 22:14 UT

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Quadrantid Radiant 3/4 Jan

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Key

he January night sky is full of splendour with mighty Orion well placed before midnight. The Hunter’s main pattern is unmistakable thanks to the straight line of three stars that form his belt. Follow the belt up and you’ll arrive at orangeKEY TO coloured Aldebaran, the brightest star in Taurus, the Bull. STAR CHARTS The V-shaped pattern of stars nearby is the Hyades open cluster. Continue the belt line through Aldebaran to reach the Pleiades, or Seven Sisters, open cluster, which is also part of Taurus. If you extend the arms of the Hyades, you’ll reach two middle-brightness stars representing the Bull’s horn tips. The lower star is Zeta (c) Tauri. M1, the Crab Nebula, lies 1.1° northwest of Zeta and requires a telescope to see it at its best. The northern horn-tip is marked by Beta (`) Tauri, or Elnath. Charts often show Elnath connecting Taurus to the misshapen pentagon of Auriga, the Charioteer, which lies to the north. This is because Elnath used to belong to Auriga before getting a transfer to Taurus. The brightest star in Auriga is the yellow sun Capella, which sits on top of the ‘pentagon’. Return to Orion and marvel at the difference between the bright white

Þ The Quadrantid meteor shower hits it peak in the first week of January

slightly dimmer than the more orangehued Pollux. Castor and Pollux define one short side of Gemini’s rectangular shape, which extends back towards Orion.

Comets and meteors Heading south from Pollux you’ll reach solitary Procyon, the brightest star in Canis Minor. There’s not much to the rest of the constellation apart from Beta (`) Canis Minoris, or Gomeisa. Canis Major can be found by extending the Belt of Orion southeast towards Alpha (_) Canis Majoris or Sirius, the brightest star in the night sky. Eight apparent full Moon diameters (4°) south of Sirius is the lovely open cluster M41, which may just about be visible with the naked eye on a cold, dark January night. Keep an eye out for Quadrantid meteors at the start of the month. The shower’s activity rises to a sharp peak during daylight on 3 January so the best time to watch will be on the nights of the 2/3 and 3/4 January. Another January highlight will be the appearance of binocular comet 45P/Honda-Mrkos-Pajdusakova visible in the evening sky at the start of January around magnitude +7.1, but switching to the morning sky by the end of the month when it will be around magnitude +8.

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39

FEBRUARY 2017

WINNER AURORAE

Twilight Aurora György Soponyai, Hungary

40

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FEBRUARY 2017

FEBRUARY The Moon takes centre stage this month, passing through Earth’s shadow

KEY DATES 1 FEBRUARY Venus, Mars and the crescent Moon are aligned from 19:00 UT

5 FEBRUARY The Moon moves through part of the Hyades cluster, passing very close to Aldebaran at 22:20 UT

10 FEBRUARY The full Moon undergoes a penumbral eclipse between 22:32 UT tonight and 02:55 UT on the 11th

17 FEBRUARY Venus is at its brightest, shining at mag. -4.6

27 FEBRUARY A chance to spot a thin 1% lit waxing lunar crescent in the west at 18:30 UT

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41

NORTH _ 9

M3

_

Deneb

FEBRUARY 2017

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STAR NAME CONSTELLATION NAME GALAXY OPEN CLUSTER

NEW MOON 26 Feb

LAST QUARTER MOON 18 Feb

ER

CHART KEY

b

PUP

MOON PHASES Key stages in the monthly cycle FULL MOON 11 Feb

S

M41

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FIRST QUARTER MOON 4 Feb

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48

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M97

M81

G

GLOBULAR CLUSTER PLANETARY NEBULA DIFFUSE NEBULOSITY DOUBLE STAR

VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

MARS

JUPITER

SATURN

URANUS

NEPTUNE

A magnificent evening planet, which is joined by Mars and a crescent Moon on 1 Feb

An evening planet close to Venus at the start of the month

A morning planet, improving over the month with the Moon close on 14 and 15 Feb

A morning planet moving from Ophiuchus into Sagittarius on 24 Feb

An evening planet, losing its favourable position throughout the month

Another evening planet, lost to the Sun’s glare during Feb

STAR-HOPPING PATH METEOR RADIANT et

VENUS

A morning planet rising 20 minutes before the Sun on 1 Feb; lost from view after the 10th

rcl

MERCURY

Ci

PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

42

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MAG. 0 MAG. +1 MAG. +2 MAG. +3 MAG. +4 & BRIGHTER & FAINTER

WEST

n

Plough

N

a

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Dubhe

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M1

FEBRUARY 2017

FEBRUARY at a glance There’s a long list of sights to see in the year’s shortest month

O

rion is slowly starting to drift westward during February so it’s a good time to get a look at the fabulous Orion Nebula, a gaseous cloud that sits in the middle of the sword hanging from his belt. At the time of our chart, the twin stars of Gemini, Castor and Pollux, ride high in the sky. To their south is lonely Procyon, the brightest star in Canis Minor, the Little Dog. Follow the line of Orion’s belt southeast to find the brightest star in the sky, Sirius – the Dog Star in Canis Major. Leo can be seen in the southeast in the period running up to midnight. If you’re unfamiliar with Leo’s shape, locate the Plough, the saucepan shape that can be found balancing on the tip of its handle in the northeast part of the sky. Find the pan of the saucepan and the two stars that form the side closest to the handle. Extend the line they make down and eventually this will bring you to Regulus, Leo’s brightest star. A backward question mark shape spreads north from Regulus and is known as the Sickle. The rest of Leo’s body spreads east of the Sickle appearing rectangular with a pointed triangle for the tail, the end of which is marked by the star Denebola. The tail points into a large semi-circle known as the Bowl of Virgo.

KEY TO

NGC 6229 26 Mar

M92

o

p

Alkaid

20 Feb & 25 Apr

HERCULES

URSA MAJOR

Plough

Comet C/2015 V2 Johnson

q

Keystone

3 May

r

CANES VENATICI

1 Feb

i2 i1

M13

Nekkar

+ +

Seginus

14 May

Kite Comet 45P/Honda-MrkosPajdusakova

20 May 13 Feb

14 Feb

12 Feb

¡

11 Feb

CORONA BOREALIS

28 May

17 Feb

16 Feb

15 Feb

b

18 Feb

19 Feb

l

BOÖTES

M3

Izar

Arcturus _

6 Jun

k

d

COMA BERENICES

/ c

Vindemiatrix SERPENS CAPUT

16 Jun

VIRGO 109

Two binocular comets will be visible in February in a similar part of the sky

o

p

24 Jun

f

28 Jun

At 22:34 UT on 10 February, the Moon enters the weak outer part of the Earth’s shadow in space known as the penumbral

shadow. This difficult-to-see eclipse continues through to 02:55 UT on 11 February, with mid-eclipse occurring Draw a line between Regulus and Castor at 00:45 UT. During midand south of its mid-point is a Background has deliberately been shown in a lighter eclipse the northern part of fuzzy patch, just visible to the N colour to allow the Earth’s shadow to be seen the Moon’s disc may appear naked eye. Binoculars trained noticeably darker than usual. on this region reveal the Beehive Penumbral E There are two reasonably Cluster, M44. This lies at the Shadow bright comets on view this centre of the faint inverted-YMoon enters month. You can find a full shaped constellation of Cancer. the Earth’s chart showing the path of Below the open part of the Y penumbral Umbral 45P/Honda-Mrkosis the sideways tear-drop shape shadow (P1) Shadow Pajdusakova on page 39. It that forms the head of Hydra at 22:34 UT Moon leaves passes close to the bright the Watersnake, the largest on 10 Feb the Earth’s globular cluster M3 on 16 constellation in the sky. Despite Greatest eclipse at penumbral 00:45 UT on 11 Feb February, which will make its size, Hydra isn’t that easy shadow (P4) a good photo opportunity. to follow, being formed largely at 02:55 UT on 11 Feb Comet C/2015 V2 Johnson from dim stars. These spread 44º altitude is well positioned to the off to the southeast of the head. north of Boötes. This should The brightest star in Hydra is 49º altitude brighten from 10th magnitude Alphard, which lies below the 40º altitude in February to mag. +6.7 head in an empty part of the during June, remaining well sky. Perhaps fittingly, Alphard Þ The Earth casts its shadow across the face of the Moon on 10-11 Feb positioned over this period. means ‘the Solitary One’.

Bees, crabs and snakes STAR CHARTS

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43

MARCH 2017 WINNER GALAXIES

M94: Deep Space Halo Nicolas Outters, France

44

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MARCH 2017

MARCH Our Galaxy moves out of view to reveal a sea of others

KEY DATES 1 MARCH A crescent Moon lies close to Mars and Uranus this evening

2 MARCH Ganymede and its shadow transit Jupiter’s disc between 22:39 UT and 04:02 UT on the 3rd

14 MARCH A bright waning gibbous Moon rises close to Jupiter at around 20:45 UT

ƨ0$5&+ Binocular comet 41P/Tuttle-GiacobiniKresak is close to the star Dubhe in Ursa Major

31 MARCH Don’t miss the crescent Moon sitting close to the Hyades and Pleiades clusters

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45

NORTH

MARCH 2017

_ MEDA

M34

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63

03

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CONSTELLATION NAME

OPEN CLUSTER NEW MOON 28 Mar

LAST QUARTER MOON 20 Mar

STAR NAME

GALAXY

MOON PHASES Key stages in the monthly cycle FULL MOON 12 Mar

Elnath

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a

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ris

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b

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LY RA

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k

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b

GLOBULAR CLUSTER PLANETARY NEBULA DIFFUSE NEBULOSITY DOUBLE STAR

VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

MARS

JUPITER

SATURN

URANUS

NEPTUNE

An evening planet at the start of March passing the Sun on 25th after which time it’s a morning object

An evening planet with the Moon nearby on 1 and 30 Mar

Well positioned in Virgo and approaching opposition, which occurs next month

A morning planet, low in the constellation of Sagittarius

An evening planet that is lost from view by the end of the month

Not visible this month as it’s in conjunction with the Sun on 2 Mar

STAR-HOPPING PATH METEOR RADIANT et

VENUS

Very well placed in the evening sky from the middle of the month

rcl

MERCURY

Ci

PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

46

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MAG. 0 MAG. +1 MAG. +2 MAG. +3 MAG. +4 & BRIGHTER & FAINTER

MARCH 2017

MARCH at a glance See distant galaxies with the Milky Way out of view CEPHEUS Castor

CAMELOPARDALIS

Pollux

LYNX Polaris

House

GEMINI

_ b URSA MINOR

b

Comet 41P TuttleGiacobini-Kresak

¡

o

¡

c

r

DRACO

h `

d

Lozenge

a

1 Mar HERCULES

¡

c

Sickle

d

a

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CANES VENATICI

Comet C/2015 V2 Johnson

f

h LEO MINOR

b

Thuban

g

f

e

30 Apr

7 Mar

1 Mar

+

25 Apr

e

URSA MAJOR

17 Apr

i `

a

`

GEMINI

_

Plough

_

d

j

_

6 Apr

10 Apr

c

Dubhe

g

Kochab

a

25 Mar

28 Mar

LEO

Galaxies gather

30 Apr BOÖTES

Keystone

CORONA BOREALIS

Kite

COMA BERENICES

Þ Comet 41P/Tuttle-Giacobini-Kresak crosses the night sky during March and April

T

he stars of winter gracefully give way to the subtler constellations of spring during March. At the time of our chart Leo, the Lion rides high in the sky. This is one of the rare constellations that actually resembles what its name suggests, in this case a lion facing west. The most distinctive pattern KEYis the TObackward question mark shaped here ‘Sickle’ represents Leo’s head and STARthat CHARTS mane. The bright star Regulus sits at the base of the Sickle.

The crescent Moon cosies up to the Hyades and Pleiades clusters at the end of the month

Running below Leo is the long and difficult to make out form of Hydra, the Watersnake. This is a huge constellation measuring 85° from head to tail. As it slithers into view a number of small constellations appear to ride on its back. Least distinctive and first to appear is Sextans, the Sextant. The main form of this constellation consists of three rather faint stars that aren’t terribly easy to pick out. Crater, the Cup is easier to define but by no means bright, located south of Leo’s back leg. The most eye-catching is Corvus, the Crow. The four brightest stars of this constellation form a quadrilateral pattern also known as the Sail.

Leo’s body is more or less rectangular, heading east from the Sickle. The lion is completed by the star Denebola marking the tip of the tail. In legend Leo’s tail was originally more extensive but reassigned to become Coma Berenices, or Queen Berenice’s Hair; you can see the hair off to the east of Leo. The stars here are intriguing as much of Coma Berenices is made up of the triangular open cluster Melotte 111. The cluster stars sit on the edge of vision flitting in and out of view.

Leo is known for several attractive groups of relatively bright galaxies. Midway under the body of the lion are M95, M96 and M105. A better known group is formed from M65, M66 and NGC 3628. Collectively these are known as the Leo Triplet. You’ll need a telescope to spot most of these, although M65 and M66 are visible through binoculars. The disc of the Milky Way rotates out of the way during spring, allowing us to look out at right angles to its plane and into deep space. Here, instead of the myriad of distant stars that produce the Milky Way, we can now see more distant galaxies. The Zodiacal constellation to the east of Leo is Virgo and inside a large semi-circular asterism known as the Bowl of Virgo is a region known as the Realm of Galaxies. Here you’re looking into the heart of several huge galaxy clusters and the number of galaxies in this region is high. You’ll need a telescope to spot them but it’s definitely worth taking time out to investigate the many Messier and NGC galaxies that pepper the region. March is a great time to try and find brightening comet 41P/Tuttle-GiacobiniKresak. It starts the month off to the north of the Sickle at magnitude +10.0. This comet will be visible for quite a while, reaching its peak magnitude of +6.7 around 10 April. Also, don’t miss the beautiful spring sight of the crescent Moon close to the Hyades and Pleiades open clusters in Taurus on 31 March. The Northern Hemisphere’s spring equinox occurs on 20 March at 10:29 UT.

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47

WINTER 2017

“A telescope brings out the true beauty of M35, revealing many of its 400+ members”

Stats NAME AND CATALOGUE REFERENCE: Messier 35 CONSTELLATION: Gemini OBJECT TYPE: Open cluster VISUAL BRIGHTNESS: Mag. +5.1 (naked eye) DISTANCE: 2,800 lightyears APPARENT SIZE: 28 arcminutes PHYSICAL SIZE: 24 lightyears across BEST TIME TO SEE: 1 Jan 23:30 UT. 1 Feb 21:30 UT. 1 Mar 20:00 UT

48

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A relatively young cluster at a mere 100 million years old, means there’s still dust left behind from the collapse of the cloud that formed M35, which can make it appear as a hazy patch

W IN TE R

SE TA AS RG O ETNA S L

M35

Open cluster in Gemini A hazy patch at the foot of one of the twins becomes a WULDQJXODUIRUPDWLRQƅOOHGZLWKVWDUVDV\RXJHWDEHWWHUYLHZ NAKED EYE

7KHYLHZIURPWKHJURXQG

Messier 35 is an open cluster in Gemini close to the foot of the twin Castor. The top of Castor’s legs begin at mag. +3.0 Epsilon (¡) Geminorum or Mebsuta. Proceed down the right leg to mag. +2.8 Mu (+) Geminorum or Tejat Posterior. Head west by 1.5° to mag. +3.3 Eta (d) Geminorum or Tejat Prior, also known as Propus. Finally, locate mag. +4.2 1 Geminorum, a star, which incidentally is occulted by the Sun during the June solstice. M35 can be found 1.5° to the northeast of 1 Geminorum. The cluster marks the right angle in a right-angled triangle that has Eta and 1 Geminorum as its hypotenuse. M35 is on the threshold of naked-eye visibility but should be visible on a clear, dark night as a hazy patch.

GEMINI

M35 +

_

Castor

Pollux

¡ Mebsuta

1 d

Tejat Prior

Tejat Posterior

`

BINOCULARS Getting a closer look Despite having a large apparent diameter of half a degree, about the same as the full Moon, many of the stars of M35 sit at a brightness threshold, which subdues their appearance through binoculars. This has the effect of reducing the cluster’s overall impact, especially if there’s any light pollution around. Magnitude +5.8 5 Geminorum sits half a degree east of the cluster and acts as a good visual anchor. The two brightest stars close to the core are of magnitudes +7.4 and +8.2 with a third mag. +7.6 star visible to the southeast. Most of the other cluster stars reside in a region roughly between these three, spilling over to the west. A general haze permeates the region but it’s easily lost with increased light pollution.

ISTOCK, PETE LAWRENCE X 3

TELESCOPE6HHLQJDOOWKHGHWDLO A telescope brings out the true beauty of M35, revealing many of its 400+ members. Start with a low-power eyepiece, increasing magnification gradually to get the best view. The triangular framework is enhanced by two mag. +8.5 orange stars nearby. A string of faint stars passes between the two northern stars. This is complemented by a less obvious line of stars from the southern point of the triangle towards the west-northwest. Both strings appear to converge at a small, faint arc pattern to the west. Also look out for the fainter, mag. +8.6, open cluster NGC 2158, located 25 arcminutes southwest of the centre of M35. This cluster is over five times more distant than M35, hence its more compact appearance.

M35

NGC 2158

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49

APRIL 2017

WINNER OUR MOON

From Maurolycus to Moretus Jordi Delpeix Borrell, Spain

50

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APRIL 2017

APRIL Mercury, the Moon and Lyrid meteors are this month’s must-see sights

KEY DATES 1 APRIL A good time to look for Mercury in the evening sky

3 APRIL See the lunar X appear from 22:30 BST (21:30 UT)

7 APRIL Jupiter reaches opposition; Ganymede and its shadow in transit between 19:30 and 21:55 BST (18:30 and 20:55 UT)

22 APRIL Peak of the Lyrid meteor shower

28 APRIL Daylight lunar occultation of Aldebaran, view from 18:50 BST (17:50 UT)

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51

NORTH DA

ME

`

b PE IA a

s Kid

lla

_

`

Ca

pe

a

IGA AUR

_ `

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b _

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CRATER

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`

CORVUS

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AN

`

_

CHART KEY

_

CENTA

URUS f

`

Arcturus

SOUTH

PERSEUS

CONSTELLATION NAME

OPEN CLUSTER NEW MOON 26 Apr

LAST QUARTER MOON 19 Apr

STAR NAME

GALAXY

MOON PHASES Key stages in the monthly cycle FULL MOON 11 Apr

M67

_

A

UT HW

iter Jup

4

M10

b

FIRST QUARTER MOON 3 Apr

`

MINOR

b

CANIS

R a

h

_

SE

a

_

a

DR

_

XTANS

`

s id in rg l Vi ri a p m A m 14 Ga eak P

Spica

le

Ce

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5

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M66

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M61

RA

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`

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11th

LIB

H UT SO

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tte

M98 M99 M M84 M 86 87

58

h

l

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VIRGO a

M90

M

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14th

`

M60

Regulus

M65

a sti

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at

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M100

b

ha

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M91

b

Alp

de

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HY

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M 9 M 6 95

53

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M64

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c

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te

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ne

a

M

Ki

a

R

S

to

b

r

GLOBULAR CLUSTER PLANETARY NEBULA DIFFUSE NEBULOSITY DOUBLE STAR

VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

VENUS

MARS

JUPITER

SATURN

URANUS

NEPTUNE

STAR-HOPPING PATH

A well positioned evening planet at greatest eastern elongation on 1 Apr but invisible after the 10th

A morning object best seen around 12 Apr

An evening planet not particularly well positioned

Best time to view, reaching opposition on 7 Apr. Moon appears close on 10 Apr

Morning planet in Sagittarius with the ring system nicely presented

In conjunction with the Sun on 14 Apr and not visible this month

Not visible this month

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PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

52

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APRIL 2017

APRIL 2017

APRIL at a glance X marks the spot on the Moon and Lyra the radiant for meteors

T

he Northern Hemisphere’s spring equinox occurs at the end of March and this is a time when the Sun’s apparent increase in declination is changing at its fastest for the year. Consequently, the period of daylight gets longer and the nights get noticeably shorter. This is most apparent during the month of April. Let’s start our look at the April sky by first locating the Plough, which to modern eyes resembles a saucepan and is almost overhead during the early evening. Follow the handle away from the pan maintaining its natural arc as you go. This will bring you to the bright orange star Arcturus, the alpha star of Boötes, the Herdsman. This constellation resembles a large kite with Arcturus at the sharper end. For scale, the kite is as high as the Plough is long. Continue the arc through Arcturus to eventually arrive at brilliant white Spica, the brightest star in Virgo, the Virgin. Virgo is a large and sprawling constellation. Its most distinctive pattern is an asterism known as the Bowl of Virgo, resembling a semi-circle of medium-bright KEYCurrently, TO bright Jupiter can be seen stars. south andCHARTS slightly to the east of the bowl. STAR Inside and to the north of the Bowl is a region of sky known as the Realm of Galaxies. A small telescope will show numerous examples of the hundreds of galaxies that litter this region. Go north from the Bowl to arrive at Coma Berenices or Queen Berenice’s hair, a largely faint constellation notable because part of it is made up of the triangular open cluster known as Melotte 111. On a clear, dark night the cluster sparkles as the faint stars that constitute it appear to jump in and out of view.

Going to the dogs Between Coma Berenices and the Plough lies Canes Venatici, the Hunting Dogs. This is a small constellation represented by two main stars; Cor Caroli the alpha star and Chara the beta star. Despite its seemingly diminutive size, the boundaries of Canes Venatici contain some superb

Þ Jupiter and its distinctive spot can be seen near to the Bowl of Virgo during April deep-sky objects. Here the list includes M51, the Whirlpool Galaxy, and the impressive globular cluster M3, which lies at the mid-point of a line drawn between Cor Caroli and Arcturus. Imagine a line from Alpha (_) to Beta (`) Canum Venaticorum. Draw a similar

length line at right-angles to this from Beta, towards the Plough. The end of this line will point at Y Canum Venaticorum, a star close to the limit of naked-eye visibility from an average darksky site. Point a telescope at it to reveal its true beauty as a very red-coloured star. Its informal name is La Superba and when you see it through the eyepiece you’ll realise why. If it’s clear on 3 April around 22:30 BST (21:30 UT) take a look at the Moon’s terminator, approximately one-quarter of the way up the Moon’s diameter from the south. What you’re looking for is a chance illumination that resembles the letter X. Known as the ‘lunar X’, its appearance is short lived. This month’s appearance of the X is set to peak around 00:20 BST on 4 April (23:20 UT, 3 April). The Lyrid meteor shower peaks on 22 April and with the Moon largely out of the way, this is a good time to look for Lyrid meteors. The shower has a ZHR of 18 meteors per hour but this can vary considerably. If the sky is very clear on 28 April use a telescope to see if you can catch the crescent Moon moving in front of the star Aldebaran in broad daylight.

Occultation disappearance 19:09 BST (Moon’s altitude 33°)

Occultation reappearance 20:03 BST (Moon’s altitude 25°)

Þ Daylight lunar occultation of Aldebaran, 28 April 2017. Times correct for centre of UK, aim to observe at least 15 minutes before WWW.SKYATNIGHTMAGAZINE.COM

53

MAY 2017

WINNER INSIGHT ASTRONOMY PHOTOGRAPHER OF 7+(<($5ƥ<281*

Lunar Reversal Brendan Devine, USA – aged 15

54

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MAY 2017

MAY Libra bears its claws this month and Venus puts in a daytime appearance

KEY DATES 1 MAY Favourable libration for the east and northeast limb of the Moon

5 MAY Peak of the Eta Aquariid meteor shower (ZHR 50 meteors per hour)

21 MAY Time to start looking for noctilucent cloud displays (see p61)

22 MAY A 16% lit waning crescent Moon paves the way to finding Venus during the day

31 MAY A 41% lit waxing crescent Moon lies close to Regulus in the daytime sky

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55

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VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

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STAR-HOPPING PATH

Reaches its greatest western elongation on 17 May, but not well placed this month

A bright morning object, rising 90 minutes before the Sun by the end of the month

An evening object gradually becoming lost from view in the dusk twilight

Well positioned at the start of the month but losing ground to the short nights by the end of May

Morning object visible to the northwest of the Teapot asterism in Sagittarius

A morning object not well positioned and never appearing in true darkness all month

Not visible this month

METEOR RADIANT rcl

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MERCURY

Ci

PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

56

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MAG. 0 MAG. +1 MAG. +2 MAG. +3 MAG. +4 & BRIGHTER & FAINTER

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MAY at a glance Shorter nights mean you have to pack more into less time

M

ay, June and July are challenging months for astronomy because the nights aren’t very long. August also suffers from this but there’s something comforting about the fact that the nights are gradually getting longer. The bright orange star Arcturus dominates the view to the south in our May chart. This is the brightest star in the constellation of Boötes, the Herdsman. When Arcturus is due south, Boötes is almost vertical in the sky. Look east of its eastern ‘shoulder’ to locate a semi-circle of stars known as Corona Borealis, the Northern Crown. The brightest star in this celestial arc is Gemma. Draco, the Dragon, sits between Boötes and Polaris, the North Star. The dragon winds itself around the constellation of Ursa Minor, the Little Bear, which has Polaris as its alpha star. Draco’s winding body ends with a pattern of four stars representing the dragon’s head. This pattern is known as the Lozenge.

The running man Southeast of the Lozenge lies Hercules, the Strongman, a pattern of stars that on traditional charts looks like an upsidedown stick figure running towards Boötes. At first glance, the star Rasalgethi appears KEY TO to be the stick figure’s right foot but actually out to be Hercules’s head! STAR turns CHARTS

Lunar phase

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Þ The Steering Wheel, aka Water Jar, asterism crosses paths with the Eta Aquariids in early May South of Boötes is Virgo, the second largest constellation in the sky. It takes the form of a large semi-circular bowl to the northwest joined to a roughly rectangular body. The stars forming the eastern side of the pattern are Mu (+) Virginis to the south and 109 Virginis to the north. Both are of similar brightness, which is to say pretty dim. Further southeast is a pair of brighter stars, forming a 45° line – a strange description but the lack of anything else nearby makes it work.

Venus

The Moon

Orientation and separation correct for 10:00 BST (09:00 UT) on 22 May

EQUULEUS

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These stars are part of Libra, the Scales. The upper star is Beta (`) Librae, or Zubeneschamali, and the southern is Alpha (_) Librae or Zubenelgenubi. These lovely sounding names translate as the Northern and Southern Claws, a reference to the fact that Libra was once part of Scorpius, which is just rising on our chart, southeast of Libra. The Eta Aquariid meteor shower peaks on 5 May with a ZHR of around 50 meteors per hour, although this figure can vary. There’s a bright 79% lit waxing gibbous Moon up during peak night but this is low in the west as the shower radiant rises around 02:30 BST (01:30 UT). On 22 May, if you can locate the 16% lit waning crescent Moon in the daytime sky using just your eyes, it should be possible to find Venus nearby too. The Moon is due south around 10:00 BST (09:00 UT), with Venus located 4.2°, or 8 apparent Moon diameters, to the north-northeast of it – that’s upper left as seen from the UK. Venus is very clear in daylight, as long as you have a way to find it. If you’re successful, how about trying for a star in daylight? On 31 May at 16:00 BST (15:00 UT), look for the 41% lit waxing crescent Moon 40° up in the southeast. Using binoculars or a telescope at low magnification, it should be possible to see Regulus an apparent Moon diameter from the Moon’s northern crescent cusp.

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57

JUNE 2017

WINNER PEOPLE AND SPACE

City Lights Wing Ka Ho, Hong Kong

58

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JUNE 2017

JUNE This month sees the strongman pointing the way to the serpent bearer

KEY DATES ALL MONTH Now is the time to keep an eye out for displays of noctilucent clouds

ƨ-81( Comet C/2015 V2 Johnson will be at its peak magnitude of +6.7

1 JUNE Look out for the Lunar X from 22:00 BST (21:00 UT)

3 JUNE All four Galilean moons are close to Jupiter’s disc at 22:30 BST (21:30 UT)

9 JUNE The Moon illusion may make tonight’s rising full Moon look huge

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59

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VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

MARS

JUPITER

SATURN

URANUS

NEPTUNE

Morning planet that reaches greatest western elongation on 3 Jun

Can’t be seen this month as it’s an evening object too close to the Sun

Evening planet best at the start of Jun with the Moon close by on 3 and 30 Jun

Reaches opposition on 15 Jun when it will appear at its best for 2017

Uranus is a morning object not very well positioned at present

Morning planet best seen low in the eastsoutheast at the end of the month

STAR-HOPPING PATH METEOR RADIANT et

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MERCURY

Ci

PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

60

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JUNE at a glance Dawn and dusk display the effects left by meteors on Earth’s sky Noctilucent clouds can be seen floating in the upper reaches of the mesosphere during June

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Hercules’s head is at the bottom of he Sun reaches one of this year’s the constellation, marked by the star two solstices on 21 June, a point Rasalgethi. Rasalgethi sits near another where the rate the Sun changes ‘head’ star called Rasalhague, representing declination in the sky is zero. the head of Ophiuchus, the Serpent Bearer. The June solstice is when the Sun is at its greatest north declination and is highest in Ophiuchus is rectangular with a squat triangle on top and although it’s a large the Northern Hemisphere’s sky. constellation, it’s difficult to make out. This means that UK nights are at Being a bearer of serpents, Ophiuchus their shortest so it’s a tricky month for is depicted carrying the snake Serpens. stargazing. In summer we get to see the This is a unique constellation because it is Milky Way high in the sky. Its presence split in two. To the east of Ophiuchus lies brings bright, distinct constellations Serpens Cauda, the Serpent’s Tail, with containing some superb deep-sky objects. Serpens Caput, the Serpent’s Head, to the During June, this starscape lies to the east west. Below Ophiuchus is the beautiful of the meridian at the time of our chart. KEY TO Centre stage is the late-spring constellation orange star Antares located at the heart of Scorpius. Saturn can currently be seen of Hercules, a large and sprawling group STAR CHARTS of stars with the distinctive Keystone pattern lying Watch the Lunar ‘X’ form at its centre. from 22:00 BST (21:00 UT) The Keystone is a useful on 1 June in twilight. locator for one of the The X should be fully formed by 00:00 BST on 2 June Northern Hemisphere’s (23:00 UT on 1 June) brightest globular clusters, M13, the Great Globular in Hercules. This magnificent object can just be seen with the naked eye under darksky conditions. Through binoculars it looks like a fuzzy star but its true majesty is revealed through the eyepiece of a telescope. It’s estimated that there are between 100,000 and 1,000,000 stars in M13, all gravitationally bound in a sphere 145 light years across.

in the southeast corner of Ophiuchus, looking slightly yellow when compared with orange Antares.

High-flying clouds June and July are the best months for spotting noctilucent clouds. These are the highest clouds on the planet, being 76-85km up. They’re thought to form when water freezes around the tiny particulates left after a meteor vaporises in the atmosphere. They can typically be seen 90-120 minutes after sunset, low in the northwest or a similar time before sunrise low in the northeast. Bright displays may last all night passing from the northwest to the northeast as they track the position of the Sun below the horizon. It’s also worth looking out for comet C/2015 V2 Johnson as it tracks from Boötes down into Virgo this month. The comet should be at its highest predicted magnitude of +6.7 during the first half of June making it a good binocular target. Finally, turn a telescope on the Moon on 1 June to try and spot the letter X roughly one-quarter of the way up the Moon’s disc along the terminator from its southern limb. The X forms when sunlight catches sections of the rims of craters Blanchinus, La Caille and Purbach.

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61

SPRING 2017

“The thin streak of M82 seen with smaller insutruments LVDZDVKZLWKƅQH mottled structure”

Stats NAME AND CATALOGUE REFERENCE: Messier 81 and 82 CONSTELLATION: Ursa Major OBJECT TYPE: Galaxy pair VISUAL BRIGHTNESS: Mag. +6.9/8.4 (binoculars) DISTANCE: 12 million lightyears APPARENT SIZE: 21x10 and 9x4 arcminutes PHYSICAL SIZE: 95,000 & 37,000 lightyears diameter

62

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This pair of galaxies provides gloriously contrasting sights, with clear differences in their shapes and the amount of discernable structure

SP RI N G

SE TA AS RG O ETNA S L

M81/M82

Bode’s Galaxy and the Cigar Galaxy With the right equipment and light conditions you FDQƅWWZRVWULNLQJJDOD[LHVLQRQHH\HSLHFHYLHZ BINOCULARS *HWWLQJDFORVHUORRN Messier 81 and 82 are a pair of relatively bright galaxies near the Plough. Find them by drawing a diagonal line from the star in the southeast of the ploughshare, mag. +2.4 Gamma (a) Ursae Majoris, or Phecda, through the star in the northwest corner, mag. +1.8 Alpha (_) Ursae Majoris, or Dubhe. Extend this line for the same distance again and both galaxies should be in the field of a pair of binoculars (light pollution and binocular size will make a difference). M81, or Bode’s Galaxy, should be the most obvious, appearing as an oval smudge. M82 can be harder to pick out, being both smaller and fainter than M81. Larger binoculars fare better – a 15x70 pair will show both objects well.

M82 M81

SMALL TELESCOPE Get more detail A small telescope reveals both galaxies well. Despite their proximity on charts, they’re 36 arcminutes apart and it’s fairly common to see one galaxy while the other is out of view. Using a low power with which the Moon takes up less than 80% of the field of view will give you a decent view of both galaxies together. M81 has a star-like core around which the galaxy’s central bulge appears as a glowing elliptical haze. Use a magnification of 50x or more to see its delicate spiral arms. Despite being dimmer, M82’s more compact nature helps define it and its thin, linear appearance is most evident. A 100mm telescope should reveal the effects of dark lanes crossing M82.

ROCHUS HESS/CCDGUIDE.COM, PETE LAWRENCE X 3

LARGE TELESCOPE See it all Large telescopes show the beauty of this pair. The core of M81 appears bright and extensive but doesn’t show much visual structure. Increase power to study the knotted, tightly wound spiral arms. Powers between 150-250x work well but pull back if detail gets lost. The spiral arms should appear mottled with reasonable contrast at their edges. M82 is completely different. Here, the thin streak seen with smaller instruments is awash with fine mottled structure. This creates a broken, irregular appearance that’s fascinating to study. Unlike M81, M82 doesn’t appear to have an easily identifiable core. But the galaxy’s central section has more prominence as the noncore sections appear to blend into the black background sky.

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63

JULY 2017 WINNER STARS AND NEBULAE

The Rainbow Star Steve Brown, UK

64

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JULY 2017

JULY This month the Moon occults Mercury and the Milky Way dominates

KEY DATES ALL MONTH Noctilucent cloud season continues throughout the month

2 JULY Minor planet 3 Juno reaches opposition in Scutum at mag. +9.8

10 JULY Dwarf planet Pluto reaches opposition in Sagittarius at mag. +14.2

25 JULY Mercury is occulted by the Moon in daylight

30 JULY Peak of the Southern Delta Aquariid meteor shower, which has a ZHR of 25 meteors per hour

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65

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GLOBULAR CLUSTER PLANETARY NEBULA DIFFUSE NEBULOSITY DOUBLE STAR

VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

MARS

JUPITER

SATURN

URANUS

NEPTUNE

Morning planet 7° below the Pleiades on 5 Jul. Waning crescent Moon close on 20 and 21 Jul

Not visible as it is in conjunction with the Sun on 27 Jul

Evening planet now past its best for the year. Moon close on 1 and 28 Jul

Low evening planet, close to its best for the year

Improving morning planet just on the threshold of naked-eye visibility

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VENUS

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rcl

MERCURY

Ci

PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

66

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MAG. 0 MAG. +1 MAG. +2 MAG. +3 MAG. +4 & BRIGHTER & FAINTER

JULY 2017

JULY at a glance The Milky Way makes its presence felt as the month progresses Daylight lunar occultation of Mercury, 25 July 2017. Times correct for centre of UK but will vary with location.

Occultation reappearance 09:01 BST (08:01 UT, Moon’s altitude 9°)

Occultation disappearance 08:31 BST (07:31 UT, Moon’s altitude 4°)

T

he summer Milky Way moves into a good position during June but the lack of true darkness around the solstice means that it’s hard to get a decent view of it. This all changes during July as the nights start to lengthen. At the beginning of the month the difference is hardly noticeable but by the end the summer the Milky Way glows majestically, flowing through some KEY TO amazing constellations as it does so. DuringCHARTS the summer we get to look STAR towards our Galaxy’s bright core. Sadly this doesn’t get very high in UK skies but it’s a magnificent sight from more southerly latitudes. Even so, from a darksky location, the bright portion of the Milky Way we see passing through Cygnus is a breathtaking spectacle.

Swans, harps and eagles July’s dominant pattern is the Summer Triangle. This is an asterism formed by the three bright stars, Deneb in Cygnus, Vega in Lyra and Altair in Aquila. Of the three, Vega appears brightest and almost overhead at the time of our chart. Below it is a squashed-diamond pattern representing the body of the lyre or harp after which Lyra is named. Next in brightness is Altair, the alpha star of Aquila, the Eagle. This is noticeable because it has two fainter stars sitting either side of it. Deneb is the faintest star

of the Summer Triangle but appearances can be deceptive. Deneb is the alpha star of Cygnus, the Swan, a large pattern that actually does look like a giant flying swan. Inside Cygnus is a large cruciform shape known as the Northern Cross. Deneb sits at the top of the cross. Although it looks dimmer than Vega or Altair, it’s actually the brightest by a long way, once you factor in distance. Altair is closest at 16.7

lightyears, with Vega next at 25 lightyears. Deneb is so far away that it’s difficult to be precise about its distance but it’s thought to be around 800 lightyears away. If you placed all three stars at the same distance, Deneb would easily outshine the others. The Summer Triangle points down towards Sagittarius. From the UK this never fully rises above the southern horizon. The main pattern we see here is another distinctive asterism called the Teapot. The region where steam would be rising out of the spout is full of beautiful deep-sky objects such as M8, the Lagoon Nebula, and M20, the Trifid Nebula. Two dim worlds come to opposition during July close to the bright Milky Way’s core. When something reaches opposition it appears in the opposite part of the sky to the Sun. Minor planet 3 Juno reaches opposition on 2 July, in the star field rich constellation of Scutum, the Shield. Then on 10 July dim and distant Pluto comes to opposition in a region of sky northeast of the Teapot asterism mentioned earlier. On 25 July a waxing crescent Moon will occult Mercury in the daytime sky – a tricky observation as Mercury will only be magnitude +0.3 at the time. Finally, as we approach the end of the month, keep an eye out for meteors as several showers will be active at this time.

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67

AUGUST 2017

WINNER PLANETS, COMETS & ASTEROIDS

Serene Saturn Damian Peach, UK

68

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AUGUST 2017

AUGUST August begins with the Moon moving in and out of Earth’s shadow

KEY DATES 7 AUGUST The rising full Moon will be partially eclipsed in the Earth’s penumbral shadow

12/13 AUGUST Peak of the annual Perseid meteor shower – a bright Moon will interfere this year

14 AUGUST Lunar libration favours the Moon’s northwest limb

16 AUGUST From 01:00 BST (00:00 UT) the Moon passes in front of the southern part of the Hyades open cluster

21 AUGUST A small partial solar eclipse is visible from the UK

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69

NORTH

AUGUST 2017

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OPEN CLUSTER FIRST QUARTER MOON 29 Aug

GLOBULAR CLUSTER PLANETARY NEBULA DIFFUSE NEBULOSITY DOUBLE STAR

VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

VENUS

MARS

JUPITER

SATURN

URANUS

NEPTUNE

STAR-HOPPING PATH

In conjunction with the Sun on 26 Aug and not well placed

Morning planet, near a waning crescent Moon on 19 Aug and M44 on 31 Aug

Not particularly well positioned morning planet, emerging from last month’s solar conjunction

Evening planet not that well positioned. A waxing crescent Moon is close on the 25th

Evening planet due south as the sky darkens at the start of Aug

Morning planet close to Omicron (k) Piscium, rapidly improving in position during Aug

Well postioned close to Lambda (h) Aquarii

METEOR RADIANT rcl

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MERCURY

Ci

PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

70

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MAG. 0 MAG. +1 MAG. +2 MAG. +3 MAG. +4 & BRIGHTER & FAINTER

AUGUST 2017

AUGUST at a glance Two eclipses make August a busy month for our Moon

T

he Milky Way continues to be well placed during August as the skies get darker, while the Summer Triangle dominates the view. This is formed by the three bright stars Vega in Lyra, Altair in Aquila and Deneb in Cygnus. From the UK, the brightest part of the Milky Way is that which flows through Cygnus, where you should be able to see it split if you’re in a dark-sky location. This split is caused by a dark dust lane blocking light from the Milky Way’s more distant stars. It’s prominent enough to earn its own name, being called the Cygnus Rift. Alpha (_) Cygni, or Deneb, sits at the top of a large cruciform asterism called the Northern Cross. The star at the foot of the cross is Beta (`) Cygni, or Albireo. This binary star is a must see through a telescope because then you’ll make out the beautiful golden yellow primary star with its dimmer azure-blue secondary nearby. Vulpecula, the Fox, is a distinct constellation that appears to the southeast of Albireo, although in actuality it passes further north under the eastern wing of Cygnus. It’s worth looking out for a

From the UK the Moon rises partially eclipsed by the Earth’s penumbral shadow. The partial eclipse will decrease as the Moon rises, ending at 21:51 BST (20:51 UT) as the Moon leaves the shadow. During the eclipse the effect Altitude 1° on the Moon from the at 21:00 BST penumbral shadow will (20:00 UT) be quite subtle

Penumbral shadow

Umbral shadow

ESE 7 August 2017

small group of stars known as Brocchi’s Cluster, or the Coathanger Cluster, after the pattern it forms in the southern part of Vulpecula. These stars aren’t actually connected but rather a chance line-of-sight asterism. Binoculars or a telescope on low power will give you the best view of it. Southeast of Vulpecula is Sagitta, the Arrow, a small constellation that looks like an arrow pointing east. Further southeast still is the constellation of Delphinus, the

Greatest eclipse

Dolphin, formed by a diamond pattern with a tail. This tight pattern is sometimes mistaken for the Seven Sisters open cluster, which is in Taurus. Southeast of Dephinus is Equuleus, the Foal, a tiny, indistinct pattern. Below Equuleus is the larger, sprawling Aquarius, the Water Bearer. The most readily identifiable pattern here is the Water Jar asterism, which is said to resemble a three-spoke steering wheel. Southwest of Aquarius is the triangular form of Capricornus, the Sea Goat, made up of a downward-pointing triangle with two pairs of stars marking the east and west vertices.

Eclipses First contact (C1)

LOCATION

C1

Belfast

18:37:56

19:00:52

19:23:25

3.090

0.088

Brighton

18:40:47

19:05:37

19:29:58

4.400

0.111

Cardiff

18:41:09

19:08:20

19:34:51

5.700

0.133

Dublin

18:38:31

19:03:00

19:27:00

3.800

0.101

Edinburgh

18:38:03

18:58:15

19:18:11

2.140

0.069

Glasgow

18:37:48

18:58:34

19:19:02

2.300

0.072

London

18:40:30

19:04:35

19:28:13

3.970

0.104

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19:02:01

19:24:16

3.140

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Norwich

18:40:11

19:02:31

19:24:28

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18:40:30

19:07:16

19:33:25

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All times are UT

G.ECLIPSE

C4

AREA HIDDEN

DIAMETER OBSCURED

Fourth contact (C4)

From the UK, the solar eclipse ends (C4) with the Sun approaching the west-northwest horizon. For those in the southeast, the Sun may set before the end of the eclipse.

There are two eclipses during August. The first is a penumbral lunar eclipse that will be hard to see. This occurs when the Moon passes through the weak outer part of the Earth’s penumbra shadow. The eclipse, which occurs as the Moon rises on 7 August, is actually the final stages of a true partial eclipse of the Moon, caused by the Moon clipping the darker umbral shadow of the Earth. Unfortunately for skywatchers in the UK, this occurs while the Moon is below the horizon. Moonrise from the centre of the UK is at 20:47 BST (19:47 UT) varying slightly with location. The second eclipse takes place on 21 August when the Moon’s disc clips the southern edge of the Sun. This will be all UK skywatchers get to see of a much anticipated total solar eclipse crossing continental North America. As ever with the Sun, only ever view it through a certified solar safety filter.

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71

SEPTEMBER 2017

WINNER ROBOTIC SCOPE

Iridis Robert Smith, UK

72

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SEPTEMBER 2017

SEPTEMBER There’s plenty of planetary activity in the month of the autumn equinox

.(<'$7(6 ƨ6(37(0%(5 Morning planet Venus passes south of the Beehive Cluster, M44

6(37(0%(5 Neptune reaches opposition

6(37(0%(5 Mercury is at greatest western elongation (18°)

ƨ6(37(0%(5 Mercury and Mars are close in the morning sky

6(37(0%(5 A lovely morning alignment of Mercury, Mars, a thin waning crescent Moon and Venus

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73

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SEPTEMBER 2017

OPEN CLUSTER FIRST QUARTER MOON 28 Sep

GLOBULAR CLUSTER PLANETARY NEBULA DIFFUSE NEBULOSITY DOUBLE STAR

VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

MARS

JUPITER

SATURN

URANUS

NEPTUNE

Morning planet passing the Beehive Cluster M44, at the start of the month

Morning object slowly pulling out of the dawn twilight

Evening planet too low for serious observation. Thin crescent Moon nearby on the 22nd

Visible in the evening sky and worth a look to see its wide open rings

Morning planet reaching its highest point in the sky in darkness all month

Reaches opposition on 5 Sep and is visible all night long throughout September

STAR-HOPPING PATH METEOR RADIANT et

VENUS

Morning planet at greatest western elongation on 12 Sep

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MERCURY

Ci

PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

74

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MAG. 0 MAG. +1 MAG. +2 MAG. +3 MAG. +4 & BRIGHTER & FAINTER

SEPTEMBER 2017

SEPTEMBER at a glance The September skies play host to some lovely close approaches dimmer Nu (i) Andromedae. To the northwest of Nu is M31, the Andromeda Galaxy and despite being 2.5 million lightyears away, it can still be seen with the naked eye. Extend the western side of the Great Square north and to the west of this line point you’ll find a collection of stars representing Lacerta, the Lizard.

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If you’re an early riser then there’s a treat in store at the start of September as Venus can be seen passing 1.5° to the south of the centre of the Beehive Cluster, M44. Both Venus and the cluster should fit in the field of view of a pair of binoculars. This also makes for a great photographic target. Spot them above the east-northeast horizon from 04:00 BST (03:00 UT). Between 16 and 18 September the early morning sky will be something to behold. On 16 September Mercury and Mars will be 0.5° apart and visible around 05:20 BST (04:20 UT). At this time Mercury will be to the west of Mars. The following morning they swap sides with Mercury now 20 arcminutes to the east of Mars. On the 18th, take in the wider view as Mercury, Mars, a 4% lit waning crescent Moon and Venus all line up around 05:50 BST (04:50 UT). On the 19th the Moon will be the object closest to the Sun, showing a very slender 1% lit waning crescent phase.

1 Sep

CANCER

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3 Sep

4 Sep

Þ Location of Venus at 04:30 BST (03:30 UT) as it passes the Beehive Cluster, M44. The planet and the cluster will be low in the east-northeast at this time

T

he Northern Hemisphere’s autumn equinox occurs on 22 September, a time when the nights are growing longer at their fastest rate. This allows us to see the bright part of the Milky Way flowing through the Summer Triangle. However, this region of sky is starting to drift westwards in the run up to midnight. In its place is one of the more familiar patterns of the autumn sky: the Great Square of Pegasus. It’s an odd formation, partly because it’s not truly square but also because only three of its stars belong to Pegasus. Its northeast corner is Alpheratz, the alpha star of Andromeda. Despite its shortcomings it’s still useful for locating other celestial objects. For example, trace a line down the square’s western side towards the horizon to find Fomalhaut, the alpha star of Piscis Austrinus, the Southern Fish. This is the most southerly first-magnitude star visible from the UK and is easily lost behind foreground objects above the horizon. Directly south of the Great Square is a faint circular pattern called the Circlet that represents the western fish of Pisces.

Following a diagonal path northeast across and out of the Great Square, bending slightly south as you go, brings you to Beta (`) Andromedae or Mirach. Slightly north of Mirach is dimmer Mu (+) Andromedae and north of that, even 16 Sep

17 Sep

18 Sep

Mercury

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Mercury, Venus, Mars and the Moon 17 September at 05:40 BST (04:40 UT)

Mercury

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Moon, 18 Sep

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Mars

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SUMMER 2017

“What you’re seeing is the integrated light from 70,000 stars all gravitationally bound within a sphere measuring 97 lightyears across”

Stats NAME AND CATALOGUE REFERENCE: Messier 22 CONSTELLATION: Sagittarius OBJECT TYPE: Globular cluster VISUAL BRIGHTNESS: Mag. +5.1 (naked eye) DISTANCE: 10,400 lightyears APPARENT SIZE: 32 arcminutes PHYSICAL SIZE: 97 lightyears diameter

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Around 70,000 stars reside in M22 helping it to look spectacular despite its low UK altitude

SU M M ER

SE TA AS RG O ETNA S L

M22

Globular cluster in Sagittarius Sitting low in the sky but densely packed with stars, M22 is one of the closest globular clusters to Earth NAKED EYE

The view from the ground

Messier 22 is a bright and impressive globular cluster in Sagittarius. It’s somewhat muted from the UK due to its low declination but in clear skies provides hints of its true majesty. Under dark conditions it can just about be seen with the naked eye and its position in Sagittarius helps. Although we can’t see the entire constellation from the UK, we do get a view of an asterism called the Teapot that sits at the heart of Sagittarius. M22 is 2.5° northeast of Lambda (h) Sagittarii, the star at the top of the Teapot’s lid. Another way to find it is to follow the two stars that mark the eastern side of the Teapot’s handle, Sigma (m) and Tau (o) Sagittarii. Follow the line they make 1.6x further on to the northeast to arrive at M22.

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SAGITTARIUS

BINOCULARS Getting a closer look

JOHN CHUMACK/SCIENCE PHOTO LIBRARY, PETE LAWRENCE X 3

It’s often said that the finest globular cluster visible from the UK is M13 in Hercules, although some argue that M5 in Serpens is preferable. M22, however, is brighter than either of them and despite being lower is easy to see in binoculars. To do so, use the Teapot asterism. Centre up on Lambda (h) Sagittarii, or Kaus Borealis, at the top of the lid. When close to its highest position in the sky, due south, M22 will appear at the 10 o’clock position in the binocular view. The globular looks like a circular smudge of grey light. This may not sound that exciting, but bear in mind that what you’re seeing is the integrated light from 70,000 stars all gravitationally bound within a sphere measuring 97 lightyears across.

M22

TELESCOPE Seeing all the detail

N

A telescope shows the spectacular nature of M22. A 150mm instrument will show individual stars crossing the hazy core. Start off with a power around 50x and increase until you get a detailed view. A 250mm scope shows many outlying stars creating a halo around what looks like a slightly elongated core. A 300mm scope will resolve most of the cluster stars, presenting a magnificent view through the eyepiece. The apparent diameter will be around 20 arcminutes, but this can be affected by how much light pollution you have to look through. Reducing the power reveals a red, mag. +8.6 star to the northeast of the core. To the south are two notable strings of stars that almost resemble dangling legs.

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OCTOBER 2017

WINNER SIR PATRICK MOORE PRIZE FOR BEST NEWCOMER

Large Magellanic Cloud Carlos Fairbairn, Brazil

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OCTOBER 2017

OCTOBER A packed month of planets, meteors and Moon craters

KEY DATES 5 OCTOBER Venus, Mars and Sigma Leonis form a tight triangle in the morning sky

15 OCTOBER A chance to spot Regulus just north of the Moon in daylight at 12:30 BST (11:30 UT)

19 OCTOBER Uranus reaches opposition

21 OCTOBER The Moon’s libration gives a favourable view of giant crater Humboldt

21/22 OCTOBER Peak of the annual Orionid meteor shower

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STAR NAME

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GLOBULAR CLUSTER PLANETARY NEBULA DIFFUSE NEBULOSITY DOUBLE STAR

VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

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NEPTUNE

Bright morning planet very close to Mars on 5 Oct

Morning planet close to Venus at the start of the month

In solar conjunction on 26 Oct so not a viable target this month

Evening planet, rather low in the southsouthwest as the sky darkens

Reaches opposition on 19 Oct and well placed all month

In Aquarius, reaching its highest point in the sky, due south. In darkness all month

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Poorly located this month and unlikely to be seen

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MERCURY

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PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

80

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MAG. 0 MAG. +1 MAG. +2 MAG. +3 MAG. +4 & BRIGHTER & FAINTER

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OCTOBER 2017

OCTOBER at a glance The Orionid meteor shower lights up the late-October sky

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ctober’s sky is full of promise. Our main chart shows the constellations of autumn with Pegasus dominating the view high to the south. The main pattern here is the Great Square of Pegasus. Count how many faint stars you can see within the square boundary. If you get seven or more you have a good, dark sky. The Square’s west side points down to Fomalhaut, the alpha star of Piscis Austrinus, the Southern Fish. The east side points down to Beta (`) Ceti or Deneb Kaitos, the ‘whale’s tail’. Cetus, the Whale, is an indistinct constellation occupying a large area northeast of Deneb Kaitos. The constellation of Pisces has two faint lines of stars running east and south of the Great Square of Pegasus. The western fish is represented by the Circlet, a circle of dim stars south of the Great Square. Trace the line of stars going east of the circlet to Alpha (_) Piscium, or Alrescha. From there it turns sharply to head northwards to form the poorly defined second fish. Uranus is currently northwest of Alrescha. Return to the Great Square of Pegasus and look for the wedge of stars spreading Catch a view of the giant crater Humboldt between 21-23 October

Orionid Radiant 21/22 Oct

10 Oct

ORION

20 Oct

30 Oct Betelgeuse

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MONOCEROS

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Rigel 21 Oct 3% wa xing crescent Sets at 19:15 BST (18 :15 UT)

Þ The Orionids’ radiant lies between the constellations of Orion and Gemini from its northeast corner. This is the body of Andromeda, the Chained Princess. Located just to the north of the mid-point of the wedge is the Andromeda Galaxy, M31. At 2.5 million lightyears, this is the furthest object you can see with the naked eye, although strong light pollution will hide it. North of Andromeda is W-shaped Cassiopeia, the Seated Queen. This pattern is circumpolar from the UK, meaning its close enough to the North Star, Polaris, to never set. Polaris is easy to find. First locate the Plough, which is shown on our chart low in the north at this time of year. Extend the line that runs

through Merak and Dubhe up from the horizon until you arrive at Polaris. Keep this line going to arrive at Gamma (a) Cephei, or Er Rai. This is part of Cepheus, the King. Cepheus looks like the outline of a child’s drawing of a house. There’s a faint variable star, just below the mid-point of the bottom of the house, called Mu (+) Cephei, or Herschel’s Garnet Star. This is well worth hunting down with binoculars or a telescope as it appears deep orange in colour.

The Harvest Moon The Moon will be full on 5 October and being the closest one to the Northern Hemisphere’s autumn equinox it’s technically the Harvest Moon. Between 21-23 October try and get a look at the waxing crescent Moon as the sky darkens. The Moon’s libration and phase will present us with a good view of the giant 207km-diameter crater Humboldt. The 21 October Moon sets around 19:15 BST (18:15 UT) producing optimal conditions to enjoy this year’s Orionid meteor shower, which happens to peak on that night. The shower has a ZHR of 20 meteors per hour, which will all appear to emanate from a location not far from the red supergiant star Betelgeuse in Orion.

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81

NOVEMBER 2017

WINNER SKYSCAPES

Binary Haze Ainsley Bennett, UK

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NOVEMBER 2017

NOVEMBER A packed month of astronomical activity promises amazing sights

KEY DATES 5 NOVEMBER Lunar occultation of the Hyades begins early evening

6 NOVEMBER Moon occults Aldebaran in the early hours

13 NOVEMBER Morning planets Venus and Jupiter appear just 16 arcminutes apart at 07:00 UT

17 NOVEMBER Lovely arrangement of Jupiter, Venus and a thin crescent Moon in the morning sky

17 NOVEMBER Peak of the annual Leonid meteor shower, which has a ZHR of 10 meteors per hour

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GLOBULAR CLUSTER PLANETARY NEBULA DIFFUSE NEBULOSITY DOUBLE STAR

VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

MARS

JUPITER

SATURN

URANUS

NEPTUNE

Morning planet, having a close encounter with Jupiter on 13 Nov

Poorly positioned morning planet

Morning planet, close to Venus on 13 Nov and forms a triangle with Venus and the Moon on 17 Nov

Difficult evening planet, potentially visible for a short time after sunset

An evening planet well positioned in Pisces

Evening planet in Aquarius, well placed all month

STAR-HOPPING PATH METEOR RADIANT et

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Evening planet, reaching its greatest eastern elongation on 24 Nov but not well placed

rcl

MERCURY

Ci

PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

84

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MAG. 0 MAG. +1 MAG. +2 MAG. +3 MAG. +4 & BRIGHTER & FAINTER

NOVEMBER 2017

NOVEMBER at a glance There’s a nice close conjunction and a grand lunar occultation Andromeda from Cetus by cutting off the head of the Gorgon Medusa, then showing the severed head to Cetus, which subsequently turns to stone. The star Algol represents the winking eye of the Gorgon.

Clusters and conjunctions November starts with a well placed lunar occultation of the Hyades open cluster. Start watching from 18:40 UT on 5 November as the Moon approaches Gamma (a) Tauri, which marks the pointed end of the V-shaped cluster. The climax occurs around 02:30 UT on 6 November as the 94% lit waning gibbous Moon hides bright Aldebaran from view. Later in the month, don’t miss the close conjunction between the bright planets Venus and Jupiter, visible in the morning sky on 13 November. Four days later on 17 November, Venus, Jupiter and a 1% lit waning crescent Moon form a beautiful right-angled arrangement also in the morning sky. Later that evening don’t forget to keep a look out for Leonid meteors. This shower peaks on 17/18 November when the Moon is virtually new and conveniently out of the way.

CANCER M44

LEO MINOR 10 Nov

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he stars of winter begin encroaching from the east during November, but before they arrive, there’s still plenty to see in the autumn sky. Wedge-shaped Andromeda, the Chained Princess, rides high in the sky on our chart, the wedge appearing to emanate from the northeast corner of the Great Square of Pegasus. Just above the mid-point of the wedge lies the Andromeda Galaxy, M31. Sitting 2.5 million lightyears away from Earth, it’s the furthest object you can see with the naked eye under normal sky conditions. The faint constellation of Pisces runs close to the eastern and southern edges of the Great Square of Pegasus. The faint stars appear to converge at a sharp point, which indicates the direction to follow to reach Cetus, the Whale or Sea Monster. This is a large, sprawling constellation that lacks any real form. Follow the east side of the Great Square of Pegasus south to locate Deneb Kaitos, the bright star marking the whale’s tail. There’s a fairly easy to identify quadrilateral of fainter stars northeast of Deneb Kaitos. The southernmost star in this pattern is Tau Ceti, a Sun-like star ‘only’ 11.9 lightyears away. It’s believed to be orbited by five planets, one of which excitingly lies in the star’s habitable zone. The head of Cetus is represented by a pattern that looks like a misshapen 50p piece. Alpha (_) Ceti, or Menkar, marks

the eastern extent of this pattern. North of the head lies the constellation of Aries, the Ram. The three brightest stars of Aries form what’s best described as a ‘bent line’, the brightest star being Alpha (_) Arietis, or Hamal. The rest of Aries spreads off towards the east. North of Aries lies the curiously named Triangulum, the Triangle, unsurprisingly formed from three principal stars. It’s curious because any three stars form a triangle unless they’re in a straight line. In mythology Triangulum represents the triangular-shaped island of Sicily. Triangulum contains the beautiful face-on spiral galaxy M33, the Triangulum Galaxy. This lies northwest of Alpha (_) Trianguli, or Rasalmothallah, and despite a relatively bright catalogue listing can be challenging to see because of its low surface brightness. To the northeast of Triangulum you’ll find Perseus, the Greek Hero, resembling a distorted lower-case Greek letter Pi (/). At the bottom of the western leg lies Beta (`) Persei, or Algol. This is an eclipsing binary dimming in brightness for around 10 hours every two days, 20 hours and 49 minutes. In mythology, Perseus rescues

Sic

Venus and Jupiter in close conjunction back in 2014; this month they appear just 16 arcminutes apart on the morning of 13 November

URSA MAJOR

Leonid radiant 17/18 Nov 20 Nov

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17 Nov Less than 1% waning crescent Sets at 16:18 UT

Þ A nearly new Moon means views of the Leonids should be good during their peak WWW.SKYATNIGHTMAGAZINE.COM

85

DECEMBER 2017

RUNNER UP PEOPLE AND SPACE

Man on the Moon Dani Caxete, Spain

86

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DECEMBER 2017

DECEMBER

The constellation of Orion holds many treasures this month

KEY DATES 8 DECEMBER Regulus reappears from behind the rising Moon this evening

13/14 DECEMBER Peak of the annual Geminid meteor shower

ƨ'(&(0%(5 An opportunity to see asteroid 3200 Phaethon – the parent body of the Geminids

22 DECEMBER Peak of the Ursid meteor shower

30 DECEMBER Lunar occultation of the Hyades with Aldebaran occulted early on 31st

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LAST QUARTER MOON 10 Dec

NEW MOON 18 Dec

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VISIBLE PLANETS Where to spot the planets this month

VARIABLE STAR THE MOON (SHOWING PHASE) COMET TRACK

MARS

JUPITER

SATURN

URANUS

NEPTUNE

Morning planet visible during the first week of Dec but lost soon after that

Morning planet closing on Jupiter. Meets with a waning cresent Moon and Juptier on 13 Dec

Morning planet improving in position throughout the month

Reaches solar conjunction on 21 Dec and not visible

Evening planet in Pisces that remains well placed throughout the month

Well placed at the start of Dec but declines in altitude towards the end

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Solar conjunction on 12 Dec after which it rapidly improves in the morning sky

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PETE LAWRENCE X 3

ASTEROID TRACK

ASTERISM MILKY WAY PLANET STAR BRIGHTNESS:

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DECEMBER 2017

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DECEMBER 2017

DECEMBER at a glance The Moon moves aside for the Geminid meteor shower this month M35 5 Dec

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10 Dec

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15 Dec

Castor 20 Dec

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he December nights are very long and full of spectacular constellations, giving you plenty of time to enjoy them. The only down side is that they’re often cold! The most striking pattern is Orion. His body is formed by seven stars, three of which lie in a straight line to make his belt. Hanging from his belt is his sword and in here lies the Orion Nebula, M42. Viewed with the naked eye, the sword has a faint allure, but with a pair of binoculars you’ll be able to see the misty form of the nebula. Through a telescope it’s an absolute delight with loads of delicate detail. The bright star in Orion’s southwest corner is blue supergiant Rigel. The opposite corner is marked by red supergiant Betelgeuse, an old star with a massive diameter estimated to be nearly 900 times greater than the Sun.

14% wa ning crescent Rises at 04:00 UT

the sky. Aldebaran sits at the end of the southern arm of the V-shaped Hyades open cluster. Despite its visual connection, Aldebaran is much closer than the cluster, being 65 lightyears away compared to the Hyades at 153 lightyears. Extend the line from Orion’s Belt through Aldebaran and you get to the Pleiades open cluster. This is about three times further away than the Minor planet 3200 Phaethon

CAMELOPARDALIS

CEPHEUS

House

1 Dec

mag +13.7

AURIGA

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6 Dec

mag +12.7

CYGNUS

12 Dec

11 Dec

mag +11.1

mag +11.4

M37

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Capella

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13 Dec

M38

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Cheshire Cat

14 Dec

15 Dec

mag +10.7

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mag +10.7

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PERSEUS

Below Orion is Lepus, the Hare, which resembles an infinity symbol with ears. To the west of Rigel and Lepus is the northern portion of Eridanus, the River. From the northern hemisphere its lacks any really bright stars. However, viewed in the southern hemisphere, Eridanus ends with the bright star Achernar, which means ‘end of the river’. Extend Orion’s Belt northwest to arrive at orange Aldebaran, the brightest star in Taurus. Its name means ‘follower’, possibly a reference to it following the spectacular Pleiades cluster, or Seven Sisters, across

Hyades, at a distance of 444 lightyears. Northeast of Taurus lies the misshapen pentagon of Auriga, the Charioteer, topped with the bright yellow star Capella. This is a rich constellation containing the open clusters M36, M37 and M38. They can be seen with binoculars but a telescope gives the best view. Northernmost M38 sits at the end of a curved line of stars forming the ‘smile’ of the Cheshire Cat asterism. The new Moon on 18 December is perfectly timed for the return of the Geminids. Emanating from a region near the star Castor in Gemini, the Geminid meteor shower has a ZHR of 120 at its peak during the early morning of 14 December. Meteor showers are normally associated with the dust debris strewn around the orbit of comets. But the Geminids’ parent body is an asteroid called 3200 Phaethon. This is unusual as it has an orbit more akin to a comet, taking it closer to the Sun than any other named asteroid. There’s a rare opportunity to spot 3200 Phaethon this month as it makes a relatively close approach to the Earth on 16 December. At 10.25 million km away it should be visible through a small telescope.

M31

ANDROMEDA

NGC 752

TRIANGULUM

16 Dec mag +10.8

Aldebaran

ORION

Pleiades

TAURUS

Alpheratz

M33

Hyades

17 Dec

ARIES

mag +11.1

18 Dec

mag +11.7

PEGASUS

Great Square of Pegasus 19 Dec

mag +12.3

Menkar

PISCES ERIDANUS

CETUS

20 Dec

mag +13.1

Circlet

Water Jar

AQUARIUS

Þ 3200 Phaeton traces a path across our skies this month and should be visible on 16 Dec WWW.SKYATNIGHTMAGAZINE.COM

89

21 Dec

mag +13.8

AUTUMN 2017

“It’s the remains of a star that went supernova in 1054 AD, an event so bright that it remained visible in daylight for 23 days”

Stats NAME AND CATALOGUE REFERENCE: M1 CONSTELLATION: Taurus OBJECT TYPE: Supernova remnant VISUAL BRIGHTNESS: Mag. +8.4 (binoculars) DISTANCE: 6,300 lightyears APPARENT SIZE: 6x4 arcminutes PHYSICAL SIZE: 11x8 lightyears

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Our most powerful telescopes are able to reveal the colourful patterns entwined around the Crab Nebula

AU TU M N

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The Crab Nebula The fallout from a massive stellar explosion that occurred almost 1,000 years ago can still be seen in today’s sky BINOCULARS Getting a closer look M1 is the Crab Nebula in Taurus. It’s the remains of a star that was seen to go supernova in the year 1054 AD, an event so bright that it remained visible in daylight for 23 days and visible to the naked eye for nearly two years. If you look at the area today you’ll see the remaining layers of star that have been blasted off into space. You can just about see M1 with binoculars but a good, dark sky is required. It looks like a faint glowing patch. The key to locating it is to first identify mag. +3.0 Zeta (c) Tauri. There’s an irregular quadrilateral formed with Zeta and three fainter stars to the north. Once you’ve identified this, M1 sits half a degree west of the mag. +6.9 star marking the quadrilateral’s northern corner.

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SMALL TELESCOPE Get more detail

WOLFGANG PROMPER/CCDGUIDE.COM, PETE LAWRENCE X 3

A small telescope shows M1 as a compact glow. Start with a low power then slowly increase the magnification to get the best view. It appears 3x5 arcminutes in size through a 150mm scope. It may seem this is all you’re going to see, but let your eye adjust to the view. Use averted vision, looking slightly off to the side, to put the nebula’s light onto a more sensitive part of your retina. With time, the elongated glow becomes a rough S shape. The darkness of your sky makes a big difference here as any brightening will cause the nebula to shrink or disappear. The Messier catalogue was created to record deep-sky objects that could be mistaken for comets and the visual behaviour of the Crab fulfils this remit perfectly.

LARGE TELESCOPE See it all The larger the aperture the more detail you’ll see. The S-shape described above becomes more pronounced, the core more elongated and brighter than the other regions. Choose a magnification that gives a good scale while retaining enough contrast and brightness to allow detail to be seen. Imaging helps bring out further details including the filamentary structures that produce the mottling you’ll see. A camera also shows what remains of the supernova star’s insides: an exotic mag. +16.5 pulsar. This was the first pulsar to be linked to a supernova and is just 20km across despite containing 1.4x the Sun’s mass. It emits a beam of radiation that we see every time the pulsar spins, at a rate of 30 times every second.

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You’ve seen the winners of 2016’s premiere astrophotography competition on the opening pages of our monthly guides and our favourite runner-up in December. Now see the rest of the runners-up and the highly commended entries

5811(56ƨ83 A runner-up prize was awarded for each main category except Robotic Scope and the Sir Patrick Moore prize for Best Newcomer

S OUR SUN Sun Flower Corona Catalin Beldea and Alson Wong, Romania and USA Equipment: CFF Telescopes 80mm f/6 oil-spaced triplet apochromatic refractor telescope, Astrotrac mount, Nikon D7200 camera

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INSIGHT ASTRONOMY PHOTOGRAPHER OF THE YEAR 2016 W AURORAE Black and White Aurora Kolbein Svensson, Norway Equipment: Nikon D750 camera, 14mm f/2.8 lens

T GALAXIES Towards the Small Magellanic Cloud Ignacio Diaz Bobillo, Argentina Equipment: Astro-Physics 130 f/5 Gran Turismo telescope, Losmandy G11 mount, Canon EOS 6D camera

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X PLANETS, COMETS & ASTEROIDS Comet Catalina Gerald Rhemann, Austria Equipment: ASA Astrograph 8-inch f/2.9 telescope, ASA DDM-60 mount, FLI PL 16803 camera

T SKYSCAPES Silent Waves of the Sky: Noctilucent Clouds Mikko Silvola, Finland Equipment: Canon EOS 6D camera, 300mm f/3.5 lens

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INSIGHT ASTRONOMY PHOTOGRAPHER OF THE YEAR 2016

S STARS & NEBULAE Perseus Molecular Cloud Pavel Pech, Czech Republic Equipment: ASA 10-inch Newtonian telescope, Gemini 53F mount, Moravian Instruments G3-11000 CCD camera, f/3.6 reducer

T INSIGHT ASTRONOMY 3+272*5$3+(52)7+(<($5ƥ<281* What the City Does Not Show You Jasmin Villalobos, USA (aged 15) Equipment: Canon EOS 1200D camera, 20mm f/3.5 lens, ISO 3200

W OUR MOON Rise Lunation Katherine Young, Sweden Equipment: Canon PowerShot SX50 HS camera, 215mm f/6.5 lens, ISO 400

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HIGHLY COMMENDED Highly commended prizes were awarded for each main category, with three prizes awarded in the Insight Astronomy Photographer of the Year – Young category

S SKYSCAPES Geminids over the LAMOST Telescope Yu Jun, China Equipment: Canon EOS 6D camera, EF 24mm f/1.4L II USM lens

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INSIGHT ASTRONOMY PHOTOGRAPHER OF THE YEAR 2016

S OUR MOON Moonrise at the Pier Sergio Garcia, Mexico Equipment: Nikon D750 camera, 600mm f/6.3 lens

W PLANETS, COMETS & ASTEROIDS King of the Planets Damian Peach, UK Equipment: Celestron C14 telescope, Celestron CI-700 mount, ZWO Optical ASI 174mm camera

T OUR SUN Huge Filaprom Gabriel Octavian Corban, Romania Equipment: Sky-Watcher Equinox ED120 Doublet refractor telescope, Sky-Watcher NEQ6 Pro mount, Pt Grey Grasshopper GS3-U3-23S6M-C camera, 3780mm f/31.5 lens, Daystar Quark +DOSKDƅOWHU

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INSIGHT ASTRONOMY PHOTOGRAPHER OF THE <($5ƥ<281*X Just Missed the Bullseye Scott Carnie-Bronca, Australia (aged 14) Equipment: Canon 70D camera, 17mm f/5.6 lens

S INSIGHT ASTRONOMY PHOTOGRAPHER OF THE <($5ƥ<281* Jupiter Olivia Williamson, UK (aged 12) Equipment: Celestron C11 Schmidt Cassegrain telescope at f/25, Sky-Watcher AZ-EQ6 GT mount, Imaging Source DMK 21AU618 camera

INSIGHT ASTRONOMY PHOTOGRAPHER OF THE <($5ƥ<281*X Northumbrian Aurora Jonathan Farooqi, UK (aged 15) Equipment: Canon EOS 550D camera, 18mm f/3.5 lens

W STARS & 1(%8/$( Starlight and Silhouettes Tom O’Donoghue, Ireland Equipment: Takahashi FSQ106N f/5 refractor telescope, Takahashi EM-200 mount, Atik 11000 CCD camera

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INSIGHT ASTRONOMY PHOTOGRAPHER OF THE YEAR 2016

S *$/$;,(6 Antlia Galaxy Cluster: Extreme Deep Field, 152 Hours Rolf Wahl Olsen, Denmark Equipment: Home-made 12.5-inch f/4 Serrurier Truss Newtonian telescope, Losmandy G11 mount, QSI 683wsg-8 camera

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Bernt Olsen, Norway Equipment: Nikon D800 camera, Nikkor 14–24mm f/2.8 lens

Robin Stuart, Kenya Equipment: Canon EOS 5D Mark III camera, 14mm f/2.8 lens

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Þ The oval Mare Crisium in the upper right changes position relative to the Moon’s eastern limb due to libration

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us and fastest when it’s closest. he Moon is the The plane of the Moon’s Earth’s nearest 5(&200(1'(' orbit is also inclined by neighbour in approximately 5° to that space and of the Earth’s orbit both orbit a common Any setup that’s capable around the Sun. centre of gravity, or of capturing the entire disc Taken together, these barycentre, which of the Moon and showing effects allow us to see lies 1,700km below the main features of the a bit more of the Moon the Earth’s surface. lunar surface, such as than we should. The Over time the Moon’s the dark seas and larger craters. speed variation allows us rotation period has to peek around the eastern synchronised with this orbit and western edges of the Moon causing it to present the same, while the inclination allows us to glimpse battered face to us throughout around the northern and southern edges. the lunar month. Well nearly… This rocking and rolling is known as The orbit is elliptical so the Moon’s libration and its effects, when combined, distance from us is constantly changing allow us to see a total of 59% of the along with its speed. This is slowest when Moon’s surface. the Moon is at its furthest distance from

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Features really close to the edge of the Moon are described as being within the libration zone. When libration is favourable for them, they can be seen with reasonable clarity. When libration is unfavourable, they won’t be visible at all. Catching a good look at a feature in the libration zones is harder than you might think. Obviously the libration needs to be favourable, moving the feature closer to the centre of the Moon’s disc. Then the phase has to be right. It’s no good having favourable libration for a feature if the phase means it can’t be seen. On top of this, the weather also has to play ball to allow you to see the favourable phaselibration window. There are various ways to see what libration will be evident on a particular date. For example, the excellent Virtual Moon Atlas (www.ap-i.net/avl/en/start), has this capability. You can see and illustrate the effects of libration by imaging the Moon’s disc over as many consecutive nights as possible, then creating an animation from the results. The vagaries of the UK’s weather mean that many sequences will be interrupted, but it’s surprising how short a window in cloud you need to actually catch the Moon – so it’s worth being tenacious! Try to capture as many sequences as you can throughout the course of the year and then use the longest for your animation.

PR O JE CT

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67(3%<67(3*8,'( Create an animation to see more of the Moon

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This project is suitable for a setup that can record a full lunar disc while also showing a reasonable amount of detail; Mare Crisium and crater Grimaldi are the bare minimum. A focal length of 400mm or longer is recommended. Full-disc shots make life easier but mosaicing highermagnification images to cover a full disc will work too.

It’s important to keep the same orientation between shots. If you’re using an equatorial mount, place the Moon in the field and slew back and forth in RA. Carefully rotate your camera so the Moon moves parallel to the upper and lower edges of your image frame. Once done, your camera will be aligned to the RA-Dec coordinate system.

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Choose the terminator region as the focus target and focus as accurately as possible. Here the stark shadows and highlights really help. If your camera allows, zoom in to make sure your focus is really sharp. Even when the Moon is full, there should still be a very thin terminator visible right on the edge.

Adjust the camera’s sensitivity and exposure to give you a correctly exposed image of the Moon. Avoid white-outs (over-exposure) or black regions on the disc (under-exposure). For DSLRs, keep the ISO relatively low, 100-200 for example. For non-tracking setups, use a higher ISO and shorter exposure to avoid motion blur.

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Load a completed sequence into a layer-based editor, one image per layer and in date order. Make all layers invisible except the bottom one. Make the next layer up visible and align with the bottom layer so the disc centres correspond exactly. Repeat this process for all the layers, aligning each one to the layer immediately below.

There are various ways to create the animation. Photoshop, for example, has a ‘timeline’ feature that lets you create animation frames with each layer. Alternatively, save each one in a lossless format such as TIF and load them into the freeware PIPP application (sites.google. com/site/astropipp) from where the animation can be created.

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3HWH/DZUHQFHguides you through the process of how to chart the changing brightness of stars

Methodically recording the brightness of a variable any of the star is a valuable way to stars visible 5(&200(1'(' keep an eye on what in the it’s doing and provide night sky scientific information vary in brightness over Any setup that can record stars that can be used to time. Most vary by down to the limit of deduce what makes it such a small amount the comparison charts, tick. Collecting this that you’d need LQFOXGLQJ'6/5ŝVƅWWHG to small telescopes information allows you specialist equipment or standard lenses. to produce a light curve: a to be able to detect it. graph that shows brightness Others, such as Omicron variations over time. There are (k) Ceti, or Mira, have such many fine organisations out there to large swings that they can change help you observe variable stars, and these the appearance of their host constellation. often have excellent resources to help Some vary periodically while others you find and select comparison stars. It’s are erratic. Examples include Beta (`) important to get these right otherwise you Perseii, or Algol, which varies predictably may end up comparing one variable star over a period of two days 20 hours and 49 with another, leading to a very confusing minutes, and R Corona Borealis, which mix of light curves. appears to have a mind of its own!

PETE LAWRENCE X 7

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Þ A time-strip image can be used to show how a variable star’s brightness changes over time

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Photographically, it’s possible to produce a strip diagram showing how a star’s brightness varies over time. Here, the difficulty is getting the exposure right so that it emulates the results from a previous session. Keeping the exposure settings the same from one night to the next is the first step, but difference between the transparency of the atmosphere from one night to the next can still cause issues. Certain software, for example Maxim DL, has routines that allow you to work out how bright an object is by comparing it to comparison stars of known brightness in the image. Such routines allow for the automatic generation of light curves from numerous images (www.cyanogen.com/ help/maximdl/Photometry.htm). To get you started, this project gives you a basic method for showing how a star varies photographically over time. The results will be approximate but should be accurate enough to allow you to produce an interesting strip diagram, or animation, to show how these objects vary. We’ve picked three stars to get you started, but if you want more, visit www. britastro.org or www.aavso.org. Our three selections are Algol, R Coronae and Mira. Algol’s variability is predictable and relatively fast. R Coronae is unpredictable and requires constant monitoring while Mira is semi-predictable, taking 332 days to complete one cycle.

PR O JE CT

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67(3%<67(3*8,'( Produce light curve charts for three stars 67(3

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Omicron (k) Ceti, or Mira, is the brightest periodic variable star that can’t be seen with the naked eye for part of its cycle. At its brightest, it competes with the brighter stars of Cetus, while at its dimmest you may struggle to locate it with binoculars. The V-shaped pattern of Pisces points directly at it.

Using the same configuration each time, centre on the target star. While not essential, keeping the field orientation the same each time can help when checking the comparison stars. If you’re using an equatorial mount, slew back and forth in RA, rotating the camera until the stars move parallel to the bottom edge of the frame. Focus accurately.

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Choose camera settings that record stars slightly below the brightness of the comparison stars described in the charts. Record these settings and take note of a faint ‘calibration’ star pattern of your choice in the first image. For subsequent images, repeat the settings, adjusting if necessary to get the star pattern looking similar between shots.

Cut narrow vertical strips of the same width from each image and assemble them along a timeline. For example, for R Coronae and Mira, each strip represents a day. Leave missed days blank. For Algol, choose a timeline to reflect a sequence over one night, possibly merging results when you have enough to show a complete recognisable curve.

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Þ The more solar activity you plot, the more the pattern formed in your diagram will resemble a butterfly. Be patient – it’ll take a long time

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of around 11 years. Over he Sun is an the course of this cycle amazing object 5(&200(1'(' sunspot numbers to observe. Its increase to a peak at appearance solar maximum, and changes from one day $Q\VHWXSZKLFKFDQ reduce to a low point to the next, delivering SURGXFHDIXOOVRODUGLVF at solar minimum. a different experience XVLQJDFHUWLƅHGZKLWH A short-term each time you view OLJKWƅOWHU$GULYHQ variability in the it. In white light the HTXDWRULDOPRXQWLV number of sunspots features of interest are KLJKO\UHFRPPHQGHG visible from one day to sunspots, slightly cooler the next is accompanied by regions of the Sun’s disc that a longer term variation in where look dark in comparison to the they occur on the disc: at the start of a surrounding photosphere. Although there cycle, spots appear at higher heliocentric are typically some spots visible each day, latitudes than at the end. Plotting where it’s not unknown for the Sun to appear spots appear throughout a cycle on a graph completely blank. of heliocentric latitude and time produces Sunspots come and go according to what’s known as a butterfly diagram due the solar-cycle, which has a visual period

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to its symmetry. This shows how spots start closer to the Sun’s poles and gradually migrate towards the equator. A true butterfly diagram plots sunspot area over time, but it’s possible to show the latitude migration fairly simply too. You don’t have to image the Sun every day but you will have to keep an eye on solar activity (via www.spaceweather.com, for example) and image the Sun whenever a new sunspot group, or active region, becomes visible. Organise the results into monthly summary strips and then join them to form the diagram. The fun thing about this project is that if you regularly image the Sun in white light, there’s little more you need to do until you’re ready to create the next strip, which can be done during those cloudy periods when you’re unable to observe. Capturing the entire solar disc in white light is something that can be done with a relatively simple setup but your telescope must be fitted with an appropriate whitelight solar filter before you point it at the Sun. Also remember to cap or remove the finder. Once you’re set up, a full-disc solar image can normally be done in just a few minutes and with the result, you have the ability to create something of real scientific interest. Just be aware that this is a very long-term project – it typically takes years for serious patterns to emerge.

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67(3 A white light filter can be made from solar film (typically £25 for an A4 sheet), card and tape. Cut it so it entirely covers your scope’s front aperture and remove or cap any finders. Use a camera set up for whole disc imaging or to cover areas that may then be mosaiced to produce the fulldisc image.

Gently applying downward pressure (pushing south) on front of the scope identifies the Sun’s north limb as the one that would first touch the edge of frame N

✓

Gently pushing the front of the scope east identifies the Sun’s west limb as the one that would first touch the edge of frame

W

67(3 Using an equatorial mount slew back-and-forth in RA. Rotate your camera until the Sun’s movement is parallel to the bottom frame edge. Pushing down gently on the scope (southwards) identifies the Sun’s north edge as that which touches the frame edge first. A gentle push east similarly identifies the Sun’s western limb.

67(3

67(3

Install WinJupos (jupos.org). Select Program>Celestial body>Sun, then Tools>Ephemerides. Enter image’s date and time. Tick ‘C.M. + equator’. Select Recording>Image measurement and open the image. Imag. tab: enter image date and time. Adj. tab: press F11 and adjust frame using N/P to match ephemerides graphic orientation.

Reselect the Image tab and save the file (F2). Select Analysis>Map computation. Click on Edit then Add and select the IMS file just saved. Choose Equirectangular projection, Planetocentric and North pole at top. Set the map width to 1,600 and click on Compile map (F12). Then save the result.

5 pixels wide

67(3

67(3

Create a new image five pixels wide and the height of the map you made in step four. Copy step four’s map into the five-pixel wide strip as a new layer. Move it horizontally and centralise on the largest spot. If other spots are visible, duplicate the layer and move that horizontally so that appears in the strip too. Set blend mode to darken to merge.

Add results for other days over the month period. Save the final strip referencing the month and year in the filename. If necessary clean the strip by painting out the dark edge extremities with the brightest surface colour. Repeat the process for each month. Add the strips side-by-side to your master butterfly diagram. Add a black strip for missed months.

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HOW TO… THERMALLY OPTIMISE YOUR TELESCOPE 2017

How to...

TOOLS AND

THERMALLY OPTIMISE YOUR

MATERIALS

TELESCOPE

Martin Lewis shows you how to combat the irritating effects of tube currents

FANS AND BATTERIES

For Newtonian mirror cooling choose a low-vibration ball-bearing or Hydro Wave-bearing electric computer fan. Power the fan from an external power supply or an on-board battery pack. RADIATOR FOIL

The aluminium-coated insulation material sold to fit behind radiators or line lofts can also be used on the outside of a telescope tube. SPACE BLANKET

A Mylar space blanket is an alternative to radiator foil and can be bought from camping and outdoor shops. Ideally, use both products. TOOLS

Scissors and insulating tape will be needed to cut and hold the radiator foil or space blanket in place.

Þ Image-disturbing tube currents can be seen silhouetted against the greatly defocused image of a bright star; the currents appear as slow swirls trapped within the disc

ALL PICTURES: MARTIN LEWIS

T

hermal dynamics can have a big influence on the views you get through your telescope, blurring planetary detail, distorting star images and degrading contrast in detailed objects such as globular clusters. If you want the best performance – whether you’re imaging or observing visually – it’s worth getting to grips with these issues so you can minimise their impact. Inside a cooling telescope, the warmer (less dense) air rises from hotter parts of the instrument as they lose heat by

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convection. These ‘tube currents’ are trapped inside the body of the telescope and, because the warmer air has a different refractive power than the cooler air, they introduce differing delays to light passing through it. This upsets the ability of your telescope’s optics to bring the light into a sharp focus. The longer the optical path inside your telescope and the more unequal the air temperatures, the greater the problems the tube currents cause. For a scope with a 1m focal length, even a 0.1°C

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temperature difference over its length is enough to degrade images. Larger telescopes are more affected than smaller ones due to their longer light path, but also because they have a smaller ratio of area to mass, meaning they take longer to cool down. Reflectors also tend to suffer more than refractors because light has to make one passage of the tube before being collected by the mirror and bent inwards away from the tube walls, where the worst convection currents often lurk. To eliminate the problematic convection currents you just need to allow every part of your telescope to cool to the ambient temperature. Thermal effects subside when the optics and other parts inside your telescope have a less than 1º C difference to the ambient temperature. When that temperature differential is less than 0.5°C, the tube currents diminish and the layer of warmer unstable air that’s otherwise stuck to the front of the mirror or primary lens

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T O STEP-BY-STEP GUIDE Ways to keep your scope at the right temperature ... Þ Insulating material, such as a space blanket, can stop your scope cooling too much

almost completely melts away – allowing maximum optical performance. Unfortunately, getting the scope to cool down sufficiently isn’t always easy. If it’s been stored indoors, then taking it out into the cold night air and expecting it to perform at its best straight away is misguided. It’s much better to store it outside before you begin observing and allow it to cool down properly. A small or medium telescope might cool down fully in 30 minutes, but a large one can take hours to acclimatise. Because air temperatures continue to fall through the night, the scope may remain a few degrees above ambient. Big telescopes also have big mirrors, and the large mass and the poor conductivity of glass mean they don’t give up their heat readily. Fans blowing gently on the back of the mirror can help here.

STEP 1

You can speed up the cooling of a Newtonian mirror by fitting an electric fan to the rear cell so that it blows onto the rear face of the mirror. If possible, mount the fan on soft rubber washers or string it between elastic bands to isolate its vibrations.

STEP 2

A low-tech alternative to installing an internal fan on your telescope is to place a desk fan nearby so that it blows on the mirror end. This will help to get the scope closer to the ambient temperature so you can start your observing session.

Insulate against the cold Even if the scope has lost all of its heat to the air, you can still get convection issues of a different kind. Parts of the telescope that face the cold night sky, particularly the top face of the telescope’s tube, can drop several degrees below ambient temperature, inducing convection currents of cold air that cascade down inside the tube. Unlike normal tube currents, which tend to die down with time, such ‘inverse’ tube current processes can plague you all night. The good news is you can combat these effects by wrapping parts of your scope in a poorly radiating material, such as shiny aluminium, or by adding a layer of insulation. The best way to check for any residual thermal issues before starting your observations is to perform a star test where you rack an eyepiece well inside focus. This allows you to clearly see any thermal currents in the tube silhouetted against the bright expanded disc of the defocused star. By following the steps to the right, you will see how badly thermal issues affect your telescope and will hopefully be able to reduce their severity to give you sharper views of the night sky.

STEP 3

Allow plenty of time for the scope to acclimatise to the outside temperature before you use it. To help speed things up, store your telescope in an unheated place, such as a shed or garage, when not in use. If it’s stored in a warm place, it’ll need longer to cool.

STEP 5

Another method of reducing inverse tube currents is to wrap a Mylar space blanket around the body of your telescope. Like the more permanent insulated foil, this reduces the radiative chilling of the telescope by the cold night air.

STEP 4

Fit the scope with a layer of aluminium-coated radiator insulation to reduce inverse tube currents caused by the cold night air, especially during still and transparent nights. This will ensure the exposed parts of the tube stay closer to ambient temperature.

STEP 6

Rack the eyepiece far inside focus to expand the image of a bright star to one-third of the field diameter. Tube currents will be seen as swirling patterns of bright and dark, trapped within the circular disc. Experiment using your hand at the front end to see the currents.

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HOW TO… MAKE A SIMPLE SOLAR FINDER 2017 WARN I

How to... MAKE A SIMPLE

NG

Do no t look directly at t h e S naked un with the e unfilte ye or any re d op instrum tical ents

TOOLS AND

MATERIALS

SOLAR FINDER

Stephen Tonkin shows you how to align your scope with the Sun in seconds with this home-made add-on

MATERIALS

12cm of 22mm-diameter copper or white plastic plumbing pipe, 22mm stop-end, 22mm brass compression straight coupler, two compression fitting inserts (if using plastic pipe), translucent plastic milk bottle, 6x30mm finder bracket. SUNDRIES

Self-amalgamating or electrical tape, safety glasses. TOOLS

Awl, drill (5mm), pipe-cutter or hacksaw, masking tape, small half-round file, vice with soft jaws, two adjustable spanners or fixed-jaw spanners to fit 22mm cap nuts (32mm across the flats), scissors, fine-tip permanent marker, craft knife.

Þ The completed finder is a great complement to any white-light solar observing setup

ALL PICTURES: STEPHEN TONKIN

N

on-solar telescopes fitted with white-light filters can be difficult to align to the Sun. One option is to make another white-light filter for your finderscope, but it’s difficult to securely fit a filter to a reflex (red-dot or projected reticle) finder; those that display a projected reticle can be permanently damaged by being exposed to the unfiltered Sun. What you need is a bespoke solar finder and we’re going to show you how to make one here. A word of caution. You must ensure that the full aperture of any instrument

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that you use to observe the Sun is covered with a proper solar filter or filter-mask combination, which you must check before each use. If you don’t check it, you risk causing instant and permanent damage to your equipment and, more importantly, your eyes. It’s essential that any solar finder is easy and safe to use, and that it should be robust enough to prevent it from being easily damaged. The safety factor is paramount – there must be no way that you can inadvertently use it to look directly at the Sun. You’ll find a solar

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finder easy to use if its bracket replaces that of the conventional or reflex finder in the telescope’s finder shoe. For this reason, we’ve used a Sky-Watcher finder bracket, which will also fit the finder shoe of several other brands of telescope. This solar finder is essentially a short pinhole camera with a recessed screen – the screen is recessed so that it can’t be easily damaged. The screen is held in place by the retaining ring in a brass compression fitting so it can’t accidentally fall out, even with vigorous shaking. Also, the finder can’t be removed from the bracket without using tools as the release collar of the stop-end fitting at the front of the finder is inaccessible, so there’s no danger of it being accidentally dismantled. The components required to make the solar finder are easily available, require minimal adaptation and are easy to assemble. They meet the robustness requirements in that they’re tried and tested for a purpose that is significantly more demanding than use in a solar finder.

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T O STEP-BY-STEP GUIDE ... %XLOG\RXURZQVRODUƅQGHUZLWKHYHU\GD\LWHPV Þ After you’ve centred the Sun once, the finder should remain perfectly aligned The stop-end we’re using is the SpeedFit; it’s a very near fit to the front end of a Sky-Watcher 6x30 finder bracket, with three or four turns of electrical tape to secure it. The circular collar on the cap-nut of the brass compression fitting is an ideal diameter for the bracket’s adjustment screws.

Practical considerations Resourceful readers can freely adapt the design so that it’ll fit a different finder bracket or can be made from alternative materials that are already to hand. For example, our prototype used the lid of a 35mm-film canister and the eye cup from a broken pair of binoculars, both of which luckily fitted a piece of focuser drawtube from our junk box. Although we had to modify the base of the finder-bracket with a hacksaw and file for it to fit the finder shoe on the telescope. The first time you use your solar finder, you’ll need to align it to the main telescope. Attach the finder and fix the telescope’s solar filter in place. Using a low-magnification eyepiece, centre the image of the Sun in the main telescope. Adjust the finder bracket’s alignment screws so that the projected image of the Sun is central on the finder screen and check the main telescope again. It usually takes only two or three attempts before the finder is properly aligned, after which it will remain permanently oriented in that position unless you adjust the alignment screws in the bracket. From then on, all you need to do is fix the telescope’s solar filter in place, attach the solar finder to the telescope and move the telescope so that the projected image of the Sun falls onto the centre of the reticle on the finder’s screen. Finding and centring the Sun now takes only a matter of seconds. This ease and speed of acquiring the target is especially valuable when you are trying to observe the Sun through gaps in the cloud on overcast days.

STEP 1

Cut two lengths of pipe: one that’s 8.5cm long for the finder body and another that’s 1.5cm long for the retaining ring that holds the screen in place. If you don’t have a pipe-cutter, wrap the pipe in paper and masking tape, and mark a ‘square-cut’ ring.

STEP 3

Cut a flat section of plastic from the milk bottle, approximately 25mm square. Use a fine-point permanent marker to draw around the end of the pipe, then draw a reticle inside the resulting circle. Carefully cut out the screen on the inside of the circle line.

STEP 5

Put the collar of the open end of the stop-end into the finder bracket and try to determine how many turns of electrical tape you’ll need to make it fit snugly. Wrap the tape onto the collar and trim it so that it won’t interfere with the release collar.

STEP 2

Use an awl or a similar tool to remove the tiny dimple in the recess in the middle of the face of the stop-end. Use the recess as a guide to drill a 5mm hole in the centre of the face. Wear safety glasses when you’re drilling.

STEP 4

Insert the screen, ink-side down, into the pipe-stop in one side of the straight coupler. Slip the compression olive over the retaining ring and push it into place. Screw on the cap-nut and use the long pipe to push the retaining ring fully home.

STEP 6

Put the long length of pipe into the compression fitting and tighten both cap-nuts half a turn. Attach the finder to the bracket, ensuring that the alignment screws bear onto the circular cap-nut collar. Push on the stop-end to secure the finder firmly in place.

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HOW TO… CLEAN A DSLR SENSOR 2017

Þ The sensor of a DSLR camera is tucked behind the reflex mirror, hence the camera has to be switched on while you clean it

How to...

CLEAN YOUR DSLR SENSOR

Blow and brush the dust from your DLSR’s sensor with Ian Evenden’s cleaning tips

ALL PICTURES: IAN EVENDEN

D

ust build-up on a camera sensor can lead to dark blobs on your DSLR images. When it comes to astronomical photos those blobs can obscure detail and darken the brightest parts of a planet or nebula – a particularly galling scenario when you’ve gone to so much trouble to capture that light in the first place. While these blobs can often be removed in imageediting software with cloning or healing tools, it’s best to treat the problem at its source. That means taking the plunge and cleaning the camera’s sensor. The sensor of a DSLR camera hides behind a reflex mirror, which deflects the light coming from the lens up into the prism that forms the viewfinder. It flips out of the way when an exposure is made

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or the camera is used in live view mode, and thus provides a certain degree of dust-proofing, but the tiny motes can, and will, still get in. The air displacement caused by zoom lenses moving their elements around, for example, can suck dust in. Dust-reducing systems are built into many modern DSLRs (look for the ‘sensor cleaning’ message on the screen as you turn the camera on and off) and these do a decent job of shaking light dust particles from the sensor by vibrating it at ultrasonic speeds.

Before and after Before you clean your sensor, take a test shot. Pop on a lens, stop it down to f/22, and take a photo of the sky during the day

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TOOLS AND

MATERIALS

Cleaning kit, air blower and brush, positionable light or a head torch, clean cloth, clean working environment. WARNING

We do not recommend you use the cans of compressed air commonly used to blast dust out of keyboards, as these can introduce moisture into the electronics of your camera.

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(taking care not to aim at the Sun, of course) or a plain white wall, then increase the contrast in an editing app. The resulting image won’t be the finest you’ve ever taken – it’ll probably be a noisy mess – but it will highlight the condition of your camera’s sensor. The dust becomes more noticeable the more you close down the lens aperture and sticks out most on a plain light background. With a magnifying glass or loupe, you’ll be able to identify individual specks of dust on the sensor using the image you just took as a guide – note that specks at the bottom of the sensor will be at the top of the picture. But taking the photo is really more useful to determine the state of the sensor. If dust is visible on the f/22 image, but not on images taken at f/2.8 or f/8, then you should consider leaving it alone until the specks become a problem. And once you’ve cleaned your sensor, you can take another f/22 photo to see the difference you’ve made.

STEP-BY-STEP GUIDE Cleanse your camera’s sensor

STEP 1

You need to get at the sensor if you’re going to clean it so the first thing to do is expose it. Most DSLRs have a cleaning option in their menus, though all models and manufacturers are different, so check the manual. Once you’ve activated it, the mirror will flip back.

TO ...

STEP 2

Use a blower to dislodge any lightly attached particles. Then lightly drag an electrostatic brush across the sensor – don’t scrub or dab as if you’re applying paint – then remove it without catching it on the lens mount and knocking the dust off. Never touch the bristles.

The right tools For large or stubborn dust particles, cleaning kits are available from most photographic retailers or online, and generally consist of a small bottle of cleaning solution and some brushes or swabs. Alternatively, a dry electrostatic brush can be used that the dust will stick to. Using the right sort of cleaning material is important, as a DSLR sensor is delicate and a scratch to its surface will do more damage than any amount of dust. Don’t be tempted to dive in with a paintbrush, a lens cleaning brush, or anything that could damage the sensitive chip. It’s possible to clean a sensor without touching it at all. Lightly attached particles of dust can be removed using a blast of air. Special blowers are available for this, some shaped pleasingly like a rocket. Hold the camera with the lens mount pointing down, then blow air up into the camera. Dislodged dust will then drift down under the force of gravity. Before you begin, clean the outside of your camera and the area you’re going to work in. This is important to prevent you adding more dust to the sensor than you remove. If you’re using a blower, keep it in a sealed plastic bag so it doesn’t collect dust and blow it into your camera’s innards. You’ll also want to make sure your camera battery is charged, as it will be on and holding its mirror open throughout the cleaning process.

STEP 3

Squeeze a few drops of cleaning solution onto a swab, not onto the sensor. You only need enough to make it damp, not so much that the solution drips off the swab when it’s held upside down. The fluid will evaporate quickly, so don’t hang about.

STEP 4

Place the swab gently on the sensor and move it from side to side. The kits are tailored to the kind of sensor you have (usually APS-C or full frame) so the swab should be the right size and you won’t have to wiggle it about to get the necessary coverage. AFTER

BEFORE

STEP 5

When you’ve completed a wipe in one direction, flip the swab over so you’re using the clean side, and use that to wipe in the other direction. Once this is done, remove the swab and dispose of it. Don’t be tempted to reuse them.

STEP 6

You’re done. Turn the camera off and the mirror should flip back into position. Attach a lens, switch it back on again, and take another reference photo to admire your work. The image above shows the same area of a sensor before and after cleaning.

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GLOSSARY 2017

Glossary (VVHQWLDODVWURQRPLFDOWHUPVGHƅQHGDQGH[SODLQHG ALTAZIMUTH MOUNT

ELONGATION

A type of telescope mount that’s simpler to set up than an equatorial mount, but requires simultaneous movement about the vertical (altitude) and horizontal (azimuth) axes to track a celestial object.

The angle in the sky between a planet and the Sun, as seen from Earth. When a planet is at greatest elongation (east or west), it is – from our perspective – at its farthest apparent distance from the Sun.

AVERTED VISION

EQUATORIAL MOUNT

A technique for observing faint objects through a telescope. It involves viewing slightly to the side of the object, allowing its light to fall on an area of the eye more sensitive to light.

A telescope mount with an axis that’s aligned parallel with the Earth’s axis of rotation. This enables stars to be tracked as they drift across the sky by moving just one axis.

BARLOW LENS

EYE RELIEF

A Barlow lens sits between a telescope’s focuser and an eyepiece, and is used to increase the magnification of an eyepiece.

The distance your eye has to be from an eyepiece for you to see the full field of view. People who wear glasses have to put their eye further away from the eyepiece and so need a longer eye relief.

CATADIOPTRIC TELESCOPE This is an optical system that uses both reflective and refractive elements. The Schmidtand Maksutov-Cassegrain telescopes are both catadioptric designs, with a lens at the front and a mirror at the back of the scope.

secondary mirror at an angle and reflected out of the side of the telescope to give a convenient viewing angle.

OPPOSITION The position of a superior planet when it’s opposite the Sun in the sky, as viewed from the Earth.

PLÖSSL EYEPIECE A type of telescope eyepiece that provides a wide field of view and good eye relief, as typically there’s a large distance between the lens and the exit pupil.

POLARSCOPE

FINDERSCOPE

A small scope that fits into equatorial mounts to help achieve an accurate polar alignment for your telescope. Accurate polar alignment is essential to take good quality, long-exposure images, where the star field needs to be tracked.

The small, low-magnification telescope that is attached parallel to a main telescope tube. It’s used to first locate celestial objects as it has a wider field of view than the main tube.

A telescope that collects and focuses light using one or more mirrors.

REFLECTING TELESCOPE

CELESTIAL EQUATOR A projection of the Earth’s equator on to the night sky.

CELESTIAL SPHERE This is the name given to the projection of the night sky on to an imaginary sphere around the Earth. The astronomical co-ordinates of right ascension and declination are also mapped on to this sphere.

FOCAL LENGTH

RGB

The distance between a telescope’s main lens or mirror and the point at which an image is brought into focus. You can work out magnification with this number, which is calculated by dividing the focal length of a telescope by that of an eyepiece.

A digital image records any colour as a combination of different intensities of red, green and blue.

MAGNITUDE

The process of aligning the optical elements of a telescope.

The brightness of an astronomical body. The lower the number, the brighter the object is. Magnitudes brighter than zero are represented with a negative number.

DECLINATION

MERIDIAN

The celestial equivalent of latitude, this is the distance of a body north or south of the celestial equator, measured in degrees, minutes and seconds (º, ‘ and “). Objects north of the celestial equator have a positive declination, while those south of the celestial equator have a negative declination.

An imaginary line circling the Earth from north to south that marks the point at which the Sun is at its highest in the sky. Ante- and post-meridiem (am and pm) respectively mark the times before and after the Sun crosses the Meridian at midday.

ECLIPTIC

A telescope that uses mirrors to collect and focus incoming light. A primary mirror collects the light, which is then intercepted by a smaller

COLLIMATION

RIGHT ASCENSION The celestial equivalent of longitude, right ascension is measured in hours, minutes and seconds (h, m and s). The 0h line is measured from the point where the Sun crosses the celestial equator on its apparent path through the sky each year, a point called the vernal equinox.

SEEING

NEWTONIAN TELESCOPE The apparent annual path of the Sun against the background stars.

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A measure of how steady Earth’s atmosphere is. When the atmosphere is turbulent, views through a telescope tend to be blurrier; this is also the reason that stars appear to twinkle.

81,9(56$/7,0(ƙ87ƚ A timescale based on the rotation of the Earth on its axis, UT is measured from midnight at the Greenwich Meridian. In astronomical use UT replaced Greenwich Mean Time (GMT), which was measured from the Greenwich Meridian at midday, on 1 January 1925.

TECHNOLOGICALLYSUPERIOR

THE NEXSTAR EVOLUTION KEEPS EVOLVING

Now paired together, enjoy the EdgeHD 8” optics and StarSense AutoAlign on the Evolution Mount. All controlled from your favourite iOS or Android phone or tablet with the new SkyPortal App.

NexStar Evolution 8” EdgeHD with StarSense AutoAlign

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Upgrade your NexStar Evolution for longer exposure astrophotography with the new Evolution equatorial wedge.

NexStar Evolution 6” SCT

NexStar Evolution 9” SCT

Equatorial Wedge

Available from specialist astronomy retailers and selected other dealers nationwide. Celestron is distributed in the UK & Ireland by David Hinds Limited. Trade enquiries welcomed.

www.celestron.uk.com Celestron® and NexStar® are registered trademarks of Celestron Acquisition, LLC in the United States and in dozens of other countries around the world. All rights reserved. David Hinds Ltd is an authorised distributor and reseller of Celestron products. The iPhone® and iPad® are trademarks of Apple Inc., registered in the U.S. and other countries.

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