Saturday 8 August 2015

Perseids, BBQ, ISS, Skelligs star party, INAM, Irish eclipse, Planetarium events

Hi all,
 
1. PERSEID METEORS MAXIMUM.
The Perseids may be the second best shower of the year, but they have the advantage of warmer nights than the December Geminids! Maximum is expected at 06.00 on the 13th, so the night of 12-13 will be best. And there's no moon to worry about this year. All you need is a clear sky and a dark location. In good conditions you could see about 1 meteor per minute on average in the early hours of the 13th.
This shower produces more fireballs than any other. The meteors are particles of debris from Comet Swift-Tuttle. Check http://spaceweather.com for updates and more information.
 
2. PERSEIDS BBQ, 12 August: The IAA will be holding another Perseids BBQ at their main observing site, Delamont Country Park, on the A22 between Killyleagh and Downpatrick. FREE! We provide the cooking facilities, you bring your own consumables, plates, cutlery etc. Meet at 8.00 p.m. for the BBQ, or 10.30 for the observing only. Bring a chair or lounger or waterproof-backed rug, and warm clothing footwear etc. Good craic, and we'll have some telescopes too.
 
3. ISS The ISS continues its series of evening passes over Ireland until 16 August. Details for your own location on the excellent and free www.heavens-above.com
 
4. SKELLIGS Star Party: 14-16 August, Ballinskelligs, Co Kerry. This is a Gold Medal winning Dark Sky site. see www.skelligstarparty.com A great programme, with interesting speakers.
 
5. INAM, QUB, 26-28 AUGUST - REGISTRATION. A reminder about the major astronomy event in Ireland of 2015 - the Irish National Astronomy Meeting (INAM), organised by the ASGI (Astronomical Science Group of Ireland). It will be held at Queen's University Belfast, from 26 - 28 August - details at Information on the 2nd Irish National Astronomy Meeting (INAM 2015, August 26-28, QUB) can now be viewed on the ASGI's website: http://www.astrophysics.ie/?page_id=660
Members of affiliated organisations such as the Irish Astronomical Association are entitled to the special discounted rate of £15 (NOTE CORRECTION!!) for the whole conference (extra for the dinner of course!)
Although early registration is now closed, it should still be possible to attend, though not to present papers or posters. More details later.
I hope to see lots of you there.
 
6. Earliest Irish eclipse? - Unfortunately, No!
Recent claims in two sources (see references in links below) say that the ancient Irish were first to record an eclipse of the Sun, in a cairn at Loughcrew in Co Meath.
But I totally debunked this theory many years ago when Paul Griffin's suggestion was referred to me for comment.
1. The eclipse was essentially invisible from LoughCrew.
(1) Maximum eclipse at that location (about 97%, not total) occurred at 17.49, when the Sun was 8.6 degrees below the horizon.
(2) The eclipse began (1st contact, which is essentially invisible) at 16.45, when the Sun was only 1 degree above the W horizon.
(3) As the Sun dipped below the horizon, maximum eclipse visible from Loughcrew would have been only about 8%, just barely visible to the naked eye, given a totally clear sky at the horizon.
2. But Paul Griffin's theory was that the local 'astronomers' viewed the very thin crescent Moon as it rose just before sunrise that morning, and were thus able to predict that an eclipse would occur later that day.
(1) But viewing such a very thin and very faint crescent Moon on the day of an eclipse is impossible with the naked eye, especially in Ireland. It has never been done anywhere in the world with the naked eye, even by experienced astronomers knowing exactly when and where to look, and from high altitude sites with exceptionally clear and transparent skies.
(2) That morning, when the Moon had reached an altitude of 1 degree (the VERY minimum necessary to see such a faint crescent), the Sun was only 3 deg 20' below the horizon - in other words it was bright twilight!
(3) The elongation of the Moon from the Sun that morning when it was 1 deg up was only 5.5 deg! And the 'age' of the Moon was 10h 14m from New. No-one has even come close to seeing the Moon so close to the Sun in Ireland, even using binoculars and knowing when and where to look!
(4) Even if they had been able to see the very thin faint crescent Moon on the previous morning, which would have been just about possible, that in itself would not have been enough for them to predict that an eclipse would occur.
3. Notable experts such as Sir Patrick Moore and Dr John Mason (the former a highly experienced lunar observer, and both very experienced eclipse observers, and both very knowledgeable in astronomy generally) totally agreed with my analysis of the circumstances.
4. For the purists, those figures are corrected for atmospheric refraction.
So, this theory is absolute nonsense, as I pointed out to Paul Griffin many years ago. That was several generations of my computers ago, so I don't have my original correspondence, especially as the theory had been so comprehensively debunked that it was not worth keeping the correspondence. (I might possibly have it on a Floppy Disc, but I've nothing to play it back on!). But that meant that I had to check all the circumstances of visibility from scratch again, ruling out any chance that I got it wrong first time round.
Much though I would like to find or agree that the ancient Irish were the first to record an eclipse, I regret that this theory does NOT establish that.
I'm amazed that this has arisen again, but unfortunately as we know, some people are more interested in publicity than astronomical accuracy.
(I should point out that Martin Brennan and Jack Roberts made no such claims about the eclipse: that claim arose more recently, as I have described above.)
However, LoughCrew is well worth a visit, especially at the equinoxes, when dawn sunlight illuminates the inner chamber.
 
7. Armagh Planetarium: News shows, and Train like a Jedi: These popular events with the Emerald Garrison will be available again at the end of August). For more details, and to book, see www.armaghplanet.com
 
8. IAA Telescopes for loan: The IAA has telescopes available to borrow, for any paid up member Enquiries to David Stewart david.stewart22@ntlworld.com or Andy McCrea s.mccrea980@btinternet.com.

9. Interesting Weblinks (now arranged by subject matter): (held over to next bulletin.
 
10.TWITTER Follow the IAA on Twitter: @IaaAstro.
 
11. JOINING the IRISH ASTRONOMICAL ASSOCIATION is easy: This link downloads a Word document to join the IAA. http://documents.irishastro.org.uk/iaamembership.doc
If you are a UK taxpayer, please tick the 'gift-aid' box, as that enables us to reclaim the standard rate of tax on your subscription, at no cost to you. You can also make a donation via Paypal if you wish: just click on the 'Donate' button. See also www.irishastro.org.
 
Clear skies,
Terry Moseley


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