CAPELLACAPELLA CAMBRIDGE ASTRONOMICAL ASSOCIATION

www.caa-cya.org Newsletter 181 July / Aug 2017 Registered Charity No. 800782

CAA / CYA SUNday Afternoon Saturday 11th June 2017

Setting up for the SUNday observing on the 11th June

More pictures on page 7

Contents this month Cover - CAA SUNday observing on the 11th June .….…. 1 Clive Gilchrist’s pictures of SUNday observing ………… 7 Chairman’s Report ……………………………….….…… 2 Usual CAA payment detailed instructions ……………….. 7 The Dobsonian on Mount Tiede Teneriffe …………...….. 2 Capella notes & Loan Telescopes ….….………………… 7 Speaker Meetings 7 - 11yr Group Meetings 8 21st Jul 2017 Gabriel Torrealba “The Milky Way +”……. 3 Sat 29th Jul 2017 “5000 yrs Keeping watch on the Sun” .. 8 18th Aug 2017 Will McMahon “Geology & Mars” ………. 3 Sat 26th Aug 2017 The Royal Greenwich Observatory …. 8 Speaker meeting review 19th May by your editor & Paul …... 4 11+ Age group Meetings 8 Messier 53 a light evening target by David Davies ………… 5 Mon 3rd Jul 2017 “Here today, gone tomorrow”………. 8 CAA/CYA Coach trip to Waterloo IMAX etc 30th Sept .. 6 Mon 26h Aug 2017 NO MEETING - HOLIDAY ………. 8 CAA contact information ……………………………….. 8

CAA & CYA Who’s who contact info page 8. 2 Cambridge Astronomical Association & Cambridge Young Astronomers

Chairman’s Report

As I write this in June we have just had our annual "SUNday" of solar observing out on the lawn of the IoA at Cambridge and were lucky with enough gaps in the clouds, to do some observing using a selection of specialised telescopes that members brought along - thank you to those who did of course.

With that, and the last few sessions of our "I-to-I" (introduction to imaging) course remaining in the next few Wednesdays we shall be going into the summer holiday period. Of course the Friday speaker meetings will continue through July and August.

I'm also happy to report that the 16" Dobsonian telescope from the loan-telescope programme, that had been languishing in my shed unused for a long time, has gone to a new and most excellent home which is suited to its capabilities... read more below.

Paul

CAA - CYA Telescope News Dobsonian Telescope installed on Mount Teide renamed “Cambridge Telescope” Story by Paul Fellows The 16" Dobsonian telescope from our pool of loan-scopes had remained unused and unloved, for around two years, in the shed and was in desperate need of a permanent home. It was just too large and heavy to be moved around, and really too heavy for a single person to get out and observe with. So we decided to dispose of it, but I was determined that it should go somewhere were it would be put to good use. I'm happy to say that we were able to do that.

Good news! It is now set up at its new base high up on the slopes of Mount Teide on the island of Tenerife at the Astronomy and Science Centre, where its large light gathering capacity is much better matched to the thin air and clear skies of that fantastic location. Mount Teide is the 3rd highest volcano and stands at 3178mtrs, just over 12,000ft which can be reached by Cablecar.

In fact the telescope currently features in the profile picture of that organisations Facebook page and has been used by many people for some stunning views of the sky.

The organisers have named it the "Cambridge" telescope in recognition of its origin, and I am in close contact with them, so if anyone finds themselves on the island on holiday and wants to get in a spot of dark-site sky watching, I can put you in touch.

The 16 inch "Cambridge" telescope in use high on mount Teide, Tenerife 3 Speaker Meetings

Speaker : Gabriel Torrealba Friday 21st July 2017 8pm "The Milky Way and its Satellites"

During his PhD Gabriel worked on developing an algorithm to systematically search for satellites of the Milky Way.

Various systematic searches for satellites were performed in the past with great success, allowing the discovery of the faintest galaxies known to date. Nevertheless, those searches were far from being complete. Since these objects are extremely difficult to find, improvements in the algorithms that perform the searches can make a huge difference. For example, allowing the algorithms to search for objects with large apparent sizes yielded the discovery of Crater 2, the fourth largest and most diffuse satellite of the Milky Way.

Gabriel is a PhD candidate at the Institute of Astronomy at the University of Cambridge. His research focuses on the study of the Milky Way surroundings to address questions like how were galaxies formed?, and how does Dark Matter shapes the outskirts of galaxies?. According to models, a galaxy like the Milky Way is expected to be surrounded by a myriad of sub-halos, but they have not been observed in the expected numbers so far. My interests include the understanding of Milky Way substructure, satellite galaxies, formation of galaxies, ultra faint dwarfs, globular clusters, ultra diffuse galaxies, variable starts/RR Lyrae, large surveys, data mining, machine learning, and performing systematic searches in the data.

Friday 18th August 2017 Speaker : Will McMahon "Geology and Mars"

Will is going to take us on a journey through the geology of Mars and what we have been able to uncover of its structure, past history and origins both from remote sensing and from the direct study by rovers, and of course the few fragments of the red planet that have found their way to Earth in the form of meteorites.

William Mcmahon is a researcher at the Department of Earth Sciences, University of Cambridge, and a graduate (MSci) from Imperial College London in Geology.

These speaker meetings will be in the Hoyle building of the Institute of Astronomy, Madingley Road, Cambridge. Doors will open at 7.30 pm. and the talks will begin at 8:00 p.m. For security reasons, entry will not be possible after 8:10pm. As usual, the library will be open before and after the lecture. Refreshments will be available after the lecture. These meetings are free to members. Non-members are charged £1 4 Editors Article Short write up of Malcolm MacCallum’s lecture 19th May 2017 Was Einstein 100% right? (About Relativity) Co written by Richard White & Paul fellows

This was another brilliant speaker meeting in which Malcolm took us for a whirlwind ride into Relativity. Starting with Newton’s picture of 3D universal space. Malcolm then enlightened us to how Einstein’s realisation that the constant speed limit for the transmission of signals by light meant he called this universality of space and time into question when observers are moving relative to each other. Despite the success of this in explaining a number of puzzles Einstein remained unhappy with Special Relativity. There real world is much more complicated with objects changing speed and accelerating especially under the effects of gravity. Newtons model of gravity could not be completely right. It suggested that the effect of gravity took no time to cross Malcolm MacCullam space, and that violated Einstein’s relativity principle. What he wanted was a new all encompassing approach that could encompass gravity, and extend it to allow for acceleration. After grappling with this for ten years he eventually pronounced - the General theory of Relativity.

He realised that acceleration and gravity were the exact same thing - if he allowed the space and time in which he worked to be curved - rather than the fixed immutable grid that Newton had assumed. This solution, defining curvature lead to testable predictions such as light bending as it passed by heavy objects first observed in 1919. This success resulted in Einstein being labelled a Scientific Genius. So the motion of the Moon and planets, and especially mercury all fell into place. Even the variations in Earth’s rotation and the positions of orbiting GPS satellites are now understood and modelled in accord with General Relativity. Without this, your sat nav could be about 1km out, rather than accurate to 4 inches.

Malcolm went on to talk about the existence of black holes as predicted by General Relativity and how X-ray’s have proved stellar mass black holes exist. This has led to the discoveries of Neutron stars and pulsars

Then he told us about the announcement of the detection of gravitational waves on Feb 11th 2016 and how hard it was to achieve as gravity is a very weak force.

Finally he covered the ideas of dark matter that has been postulated to account for the speed of rotation of galaxies and their behaviour in galaxy clusters and the even more obscure notion of Dark Energy as an anti-gravity force driving the expansion of the universe. Einstein’s equations included a term for these and have shown that they can pass every test we have put them too so far. So are they right?

However we do know that there are difficulties ahead. What happens at the very centre of a black hole? The equations blow up in your face at that point - General Relativity predicts its own failure at such points. And the other great theory of the 20th century, Quantum Mechanics, has similar issues when gravity and GR are brought into it. We know that it is impossible for both GR and QM to be 100% right. One, the other, or most likely both will have to be amended.

Malcolm concluded that we should say Einstein was at least 99% right, but it is that last 1% that keeps us searching for more conclusive proof. 5 Members Contributions Messier 53: an imaging target for light evenings. Comparison images from two telescopes by David Davies

In the middle of summer, as now, we have no astronomical darkness. That is, the sun does not set more than 18 degrees below the horizon. We now have nautical darkness, i.e. the sun is at least 12 degrees below the horizon, between, sometime after 11 p.m. and 2:30 a.m. The darkest time is around 1 a.m. This means we do not have a truly dark sky and the darkness does not last long. Therefore, deep sky imaging is so difficult that some do not bother to venture out at all.

However, star clusters provide beautiful and relatively simple targets to image and because the stars are much brighter, than say the faint spiral arms of a galaxy, they can be captured with relatively short exposures. A key aspect of imaging stars is that you do not want to use an exposure that is long enough to saturate the star images. Only by doing this can you capture the colours of the stars.

During late May, I set out to capture images of Messier 53 using two telescopes. I wanted to compare the images produced by a refractor telescope, equipped with lenses, with that produced by a Ritchey-Chretien telescope, equipped with mirrors.

Messier 53, NGC 5054, in Coma Berenices is around 60,000 light years from us and in absolute terms is larger than Messier 13 in Hercules but appears smaller and fainter due to its greater distance; the 25 brightest stars have an average magnitude of 15. The first image was captured in early May with a 107mm APM refractor. It is a simple RGB image of 30 minutes each colour in two-minute subs. This is an enlargement of that image showing Messier 53.

What we can see here are beautifully captured star images and the yellow and blue double star below and to the left of the cluster is especially lovely to look at.

Here is the same star cluster imaged with the Ritchey-Chretien telescope. This telescope has just over twice the focal length of the refractor and therefore gives half the field of view in my camera.

Although the images frame approximately the same field of view, it is apparent that the image from the Ritchey-Chretien telescope has smaller star images due to its bigger aperture. But the most striking differences to me were the colours of the stars. The refractor presented warm star tones and, for example, the yellow star to the bottom right is, truly, a yellow star; the red and blue stars in the cluster itself are beautifully distinguished. The image from the Ritchey-Chretien telescope, on the other hand, presented a much colder, almost clinical image, rather blue in its tone.

I really had to pump up the colour saturation to bring out the differences in colour.

So, I’ve learned something. Some very experienced imagers claim they prefer the images from refractor telescopes because they are warmer and more attractive than those from a telescope having only mirrors.

But lenses diffract light and, from what I have seen here, the lenses of refractor telescopes are not entirely transparent to blue light and so alter the colour balance of the image to make it warmer in tone. So I conclude that the mirrored telescope, the Richey-Chretien, produces the more accurate colour image because mirrors reflect all light equally but that might not be what people would like to see. 6

River Thames cruise aboard 7 Members Contributions SUNday observing Pictures from Clive Gilchrist

Earnest SUN viewing from the lad in the centre

Paul demonstrating the SUNday Elephant trunk pose

CAA News CAA/CYA coach trip to Waterloo IMAX cinema, River Thames cruise, Cutty Sark, National Maritime Museum, Royal Observatory & Panetarium show Greenwich on Saturday 30th September 2017 (see page 6).

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Capella Editor’s notes to members. Loan Telescopes.

Thanks to Paul Fellows and our members David Davies and Now is a good time to book a telescope especially as the Clive Gilchrist for their interesting contributions. instruments have been augmented thanks to the IoA. We have a pool of nine telescopes and one set of giant Come on please don’t be shy!! Remember you are all invited binoculars in our loan programme and all are designed to be to contribute anything as a suitable article with photos for extremely easy to use, but of course we will be happy to show Capella. It is carefully typeset, abridged if necessary and you exactly what to do. published every alternate month. Not every item can be published in the month that you submit it but we will always try Please remember that two of the telescopes will not fit in a to incorporate your articles where possible. So it could be yours standard sized car - the long focus planetary telescope and the in the next one. Behemoth. The Behemoth, especially, is not a one person telescope! As well as being big it is also heavy, and really does Please try to submit at least 4 weeks in advance of publication. need two people to shift it.

I would ask that any information you wish to include must be in The other telescopes will fit across the back seats of most cars, and standard text or preferably formatted as a Word document. If are recommended for first time users of our loan telescopes. you embed any pictures for your story, please also sent separate good quality JPG files smaller than 10mb. You can contact me Visit our website (www.caa-cya.org) and click to book an by email on any content or publication issue at instrument, or alternatively [email protected] please ring Mickey Pallett on 01480 493045. 8 CYA Meetings 7-11 Year Group

5,000yrs of keeping watch on the Sun Saturday 29th July 2017 at 10:00am

One of the reasons Stonehenge was built to measure the movements of the Sun, so our ancestors would know when days would become shorter (or longer) which helped the farmers. Over the last few hundred years we have observed the Sun with telescopes for another reason - to find out how the Sun works. More recently orbiting solar observatories are keeping an eye on solar activity every minute of every day, this time they are also looking at space weather because the Sun could dramatically affect us here on Earth.

The Royal Greenwich Observatory Saturday 26th Aug 2017 at 10:00am

Over 340 years ago King Charles II was worried about ships getting lost at sea, and had the Royal Greenwich Observatory built in London to help solve this problem. Since then sailors can successfully navigate the oceans the role of the Royal Observatory has changed, and the Observatory has also moved a couple of times during its history; to Sussex and then to Cambridge (less than 200 metres from where the CYA meetings are held) and the old observatory in Greenwich Park is now a museum and will be part of our

11+ group meetings

“Here today, gone tomorrow” Monday 3rd July 19:15pm

We will be looking at short-lived,one-off events that are seen in the sky. From strange lights on our nearest neighbour, the Moon, to transient outbursts at the furthest reaches of the Universe, some are understood yet others remain a mystery, although there is no shortage of ideas (yes, including aliens!).

This event will be hosted by members of the Cambridge Astronomical Association

NO MEETING _ HOLIDAY! Monday 7th August Paul, Brian, Avi, Clive and Darryl and the rest of the CAA team will be taking a short break while they are on their exotic holidays to distant planets in galaxies far far away.

Chairman: Paul Fellows President: Jim Hysom Treasurer & Membership Secretary: Mickey Pallett Vice President: Carolin Crawford Secretary: Michael Jenkins Vice Chairman: Brian Lister Committee: Dave Allen, Kevin Black, Paul Drake, Clive Gilchrist, Cambridge Young Astronomers (both groups): Brian Lister Tel: (evenings) Clive Holt, Barry Warman, Christopher Wright and Brenda Field. 01223 420954 or email [email protected] Capella Editor and DTP Setter: Richard White [email protected] Telescopes for hire to members: Mickey Pallett Tel: 01480 493045 or Members should send stories for inclusion where possible by email to Richard. book on -line. Alternatively send them to Brian Lister Tel: 01223 420954 (evenings) or Loan Telescope maintenance: Dave Allen, email [email protected] email [email protected] Library: Kevin Black Tel: 01223 473121 Website: www.caa-cya.org