Friday, 31 August 2012

No Blue Moon, New NEO, Sugar in space, EHODs, Book Launch, Fireball reports

Hi all,
1. BLUE MOON? - No!
They're at it again. The media, and believe it or not, a NASA 'public outreach official', are once again peddling the myth of a 'Blue Moon' tonight. (See: ) Why? because it's the second Full Moon (FM) this month.
   But as everyone knows, 'once in a blue moon' means something that's very rare, almost unbelievably so. It comes from the fact that on very rare occasions, the moon does actually appear blue, if for example a major volcanic eruption throws large amounts of very fine dust high into the atmosphere. This dust scatters the light in such a way as to turn the moon a slight shade of blue.
   And of course, such a 'genuine' blue moon does not have to occur at Full Moon - it can be seen any time when there is that sort of dust, and the moon is visible low down in a dark sky (though that is most likely to occur on the 5 or 6 days surrounding FM).
   The 'Blue Moon = FM twice in a month" myth originated with a story in Sky and Telescope magazine well over a decade ago, when they published an article saying that a 'Blue Moon' was when 2 Full Moons occurred in the same month. After many readers, including myself, pointed out that this was wrong, they later published a correction, withdrawing the appellation. But, like the genie out of the bottle, once the story is out there, it's very hard to stop it.
   And two FMs in the same month is not even a rare event - it happens 5 or 6 times every decade. For example, there will be four more occasions in this decade: 2015 Jan 2 & 31; 2018 Jan 2 & 31; 2018 Mar 2 & 31; and 2020 Oct 1 & 31. And of course, we can similarly get 2 New Moons, 2 First Quarters, or 2 Last Quarters, in the same month.
   It's very simple: the average interval between FMs (or NMs etc) is about 29.5 days. And 11 of the 12 months have either 30 or 31 days.
   It's not exactly 'rocket science' - is it, NASA?
2. Newly discovered NEO to make a close pass to Earth  (Adapted from a BAA e-circular, with thanks).
   NEO 2012 QG42 was discovered by the Catalina Sky Survey on Aug 26, and this relatively large
near-Earth asteroid will be readily observable for Irish/UK observers between September 4-14 during which time it will exceed magnitude 15.0.  It is probably between 200-500 m diameter. It will be brightest around September 10-12 when it will reach visual magnitude 13.6 on average. It passes closest to us around 05h UT on Sep 14 at a range of about 7.4 lunar-distances (0.019 AU).
   2012 QG42 is a potentially hazardous asteroid (PHA) and is unusual in that it passes very close to the opposition point on September 7. The circumstances of this close approach therefore makes it a good target for photometry (using a V, R or r' filter if possible) as well as other physical studies. An ephemeris with visibility details for UK observers is available at:
   If you are planning to observe this target then please consult the Minor Planet Center ephemeris service: to obtain exact positions for an observatory location near to your site at the time you require.
   This object should be within easy reach of many readers with modern CCD imaging equipment.
   It's a pity they didn't find it in the asterism commonly known as 'the Teaspoon', beside the Teapot in Sagittarius. Even better would be if it had been in Cr394, which looks as if it's a sugar lump being tipped out of the teaspoon. Sugar in a teaspoon in the sky would be sweet, wouldn't it? OK, so Cr394 is an open cluster, not a star-forming region, but let's not quibble. There's even another smaller cluster (NGC 6716) beside it, so you could ask 'One lump or two?'
   (The 'teaspoon' is made up of the following stars in Sagittarius: Rho1, 43, Pi, Omicron, Xi 2 and Xi1.)
4. European Heritage Open Days, 8 Sep: European Heritage Open Days (EHOD) are a once a year chance to discover hidden architectural treasures and enjoy a wide range of tours and events that bring our history and culture to life. Both Armagh Planetarium and Armagh Observatory are participating:
A. Armagh Observatory Open Day. There will be guided tours throughout the day; see: 
B. Armagh Planetarium Open free: Armagh Planetarium will be opening for a free day on Saturday 8th September.  You will get a chance to see one show of your choice for free.  Opening hours are from 10am - 5pm.  There are only a limited number of tickets for the digital theatre shows available so give us a call and pre-book your seat on 028 37523689.  Please visit for our timetable of digital theatre shows.
5. IAA MEMBER'S ECLIPSE BOOK LAUNCH IN BELFAST, 15 Sep. Remember the official launch of "TOTAL ADDICTION: The Life of an Eclipse Chaser" by IAA member Dr Kate Russo, at 3 p.m. on Sat 15 September, at the Queen's Film Theatre, University Square, Belfast. 
   Kate is both a clinical psychologist and a highly enthusiastic eclipse chaser, and she has combined the two in this fascinating book about what drives people to travel halfway round the world to see a Total Eclipse of the Sun. The simple answer is of course that it's probably the most amazing, incredible, mind-blowing, emotional spectacle that anyone will ever see. But there's much more to it than that, with lots of different motivations for seeing one, and an even greater range of reactions to the event.
   The event is free, with a documentary being shown in the film theatre, followed by some presentations by Kate and others - even including myself - followed by refreshments and a chance to get a signed copy, chat to Kate, and mingle with other astronomers and eclipse chasers. And some psychologists to, but don't let that put you off - they won't be analysing anybody!
   Everyone is welcome to attend. Details at  - and look under events.
6. Fireball Reports: Prof Mark Bailey of Armagh Observatory asked me to mention that the Observatory has a web page devoted to fireball reports: See
8. TWITTER: the IAA now has a twitter account:  @IaaAstro

9. BBC THINGS TO DO WEBSITE: See the forthcoming IAA events on  
10. JOINING the IRISH ASTRONOMICAL ASSOCIATION is now even easier: This link downloads a Word document to join the IAA. 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.  See also
Clear skies,
Terry Moseley


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