As the observing season draws to a close, what should we look out for? Clearly, Jupiter never fails to impress and will be a great target throughout May. While you’re in that area of the sky, have a go at M104, the Sombrero Hat galaxy, which is about 8° lower. Its magnitude is 8.3 so visible in any telescope or even binoculars on a moonless late evening (15th onwards). And while you’re in dark sky mode, how about the Virgo cluster of galaxies, M51, M3, the spectacular M13 and any of the objects listed here. If you get the bug, here’s a good site for all the Messier objects including finder charts. Then of course, there’s always the Moon and the Sun. For the latter, obtain some solar filter material to fix firmly and safely full-aperture over your telescope’s primary collector.

Good viewing!

Society News

Committee Meeting April 28th

Committee meeting was held, but was not quorate.  Officers present reported and valuable discussion was had.  Minutes will be issued in due course.  Of note is that we will shortly be issuing the YAS Child Protection Policy.  This has been approved at previous meetings and will be issued to all members, will be posted on the website and will be issued to all organisers of events we attend as a society as part of our outreach programme.  Paul Thornley has volunteered to be our designated Child Protection Officer.

Knavesmire Star Parties

There will be no further Knavesmire star parties until next season due to the lightness of the evenings.

Astronomy/Space/SF DVD Swap Shop

The swap shop was trialled during April. One person contributed some DVDs and one other person borrowed one, raising just £1 for society funds. The swap shop box will be at the May 5th meeting but if there is no further interest, the facility will be withdrawn.

Last month’s events – April

April 7th

YAS Friday meeting at Priory Street Centre. We were given a talk entitled “The Dark Side of the Universe” By Professor Pete Edwards of Durham University. Professor Edwards discussed how there is more to our Universe than meets the eye – a lot more. Most of what’s out there still has scientists in the dark. Astronomical observations have established that everyday matter accounts for only 5% of the cosmos. The rest is invisible to our telescopes. The professor explained that by observing gravitational lensing, we now know that 90% of the stuff of galaxies is dark matter. He went on to show that it appears that the universe, though expanding, is doing so at an increasing rate. The explanation – so the theory goes – is Dark Energy, which appears to provide a strange negative gravitational force. He concluded with an analysis of the cosmic microwave background (CMB) and how its “bumpiness” agreed with theoretical calculations of how the early universe evolved immediately following the big bang, as shown in the now famous “power spectrum” graph (below).

His final figures were that 5% of the universe is normal matter (atoms etc.), 27% is dark matter, and 68% is dark energy. Fascinating and thought-provoking stuff which demands a thorough understanding of astrophysics to appreciate it all. If you would like to try to learn more, go to the Wikipedia CMB entry. But I warn you – it’s hard going!

April 21st
YAS Friday meeting at Priory Street Centre. Alan Hawley of our society valiantly stepped up to the plate when the previously booked lecturer had to cancel, and gave us a well illustrated talk on artificial satellites. He explained how satellite orbits can be described and classified in terms of their inclination (to the equator), shape (circular or elliptical) and altitude. He also pointed out the difference between a geostationary orbit (where the satellite remains stationary relative to a particular point on the Earth’s surface) and geosynchronous (where the satellite remains above a particular line of longitude but because its orbit is inclined to the equator, is seen to drift north and south during a 24hr period). His talk also included a run through of launch systems and Hohmann Transfer Orbits. He concluded by listing the all-important on-board systems that have to be designed, developed and tested before a satellite is launched. This include the payload, propulsion, guidance, attitude control, thermal control, power sources, communications, command and data handling, and in some cases of course, life support. He certainly did a great job of convincing us that it is no mean feat to place a satellite into orbit and have it successfully perform all the tasks it was designed to do. A great talk. Well done and thank you, Alan.

For more information on some of the space-based telescopes etc., try these: Hubble, James Webb, SDO (Solar Dynamics Observatory, SOHO (Solar & Heliospheric Observatory), Herschel and Planck. For the low down on the ISS and a host of other satellites and when you can see them, go to the excellent web site, Heavens-Above.

Next month’s events – May

May 5th (Friday)

YAS Friday meeting at the Priory Street Centre. Dr Dan Brown of Nottingham Trent University will deliver a talk entitled, “A 6,000 year old telescope with no Lens”. As Senior Lecturer in the university’s School of Science & Technology, Dr Brown’s areas of research include Archaeoastronomy so I wouldn’t be surprised if we are to be given some interesting facts about sites such as Stonehenge.

May 19th (Friday)

YAS Friday meeting at the Priory Street Centre. Hazel Collett will give us a talk entitled, “The Beauty and Violence of the Sun”. Hazel Collett has been a member of the York AS since 1999, having joined shortly after the Solar eclipse in Cornwall. She was the YAS meetings secretary for many years and has also done excellent work with the BAA, gaining a medal in 2015 for her contributions. Her passion in astronomy has always been the Sun and in this talk Hazel will be sharing her passion for our nearest star.

May 20th (Saturday)

Barbecue at the observatory to mark its 10th year. All members and their families welcome. Kick off early evening. Please check with airfield club house before going airside.

Here’s a good site for upcoming sky events. It is clear and concise.

For a more detailed sky calendar, here are the BAA bi-monthly sky notes.

And here is a link to our own YAS web site.

The society also has a Facebook page

There’s a YAS Instagram page online. Go to

Finally, if you have any ideas or thoughts on how we can improve our society, speak to one of the committee or write to Derek on

We look forward to seeing you at the next meeting, on 5th May.

Clear skies!

This Bulletin compiled for the York Astronomical Society by John Rowland