From: TerryMoselaol.com
Date: Fri, 29 Apr 2005 15:25:46 EDT
Subject: Giant sunspot, ISS,  Occultation by Saturn's Rings

Hi all,

1. Look for the giant sunspot which has recently appeared: it's just West of 
centre of the Sun's disk - a real beauty! No word of any flares or CME's to 
cause possible aurorae, but you never know.... Thanks to new IAA vice president 
Pat O'Neill for the first alert.

2. The ISS is now becoming visible in the evening sky as well as the morning 
sky, as a result of the shorter nights: there are some really nice passes 
coming up. Check www.heavens-above.com for exact details of the ISS, and 
brilliant Iridium flares etc, for your own location - it's a great site, and it's 
totally free!

3. Dr Tolis Christou at Armagh Observatory alerted me to this very rare 
event! On January 25, at about 18.45, the 8th mag star BY Cancri will be occulted 
first by Saturn's Rings, and then by Saturn itself, before emerging from behind 
the planet's South Pole region. 8th mag does not sound very bright, but it's 
about half a magnitude brighter than Titan, Saturn's brightest moon. There 
have been occultations of stars by Saturn's rings before, but ones by stars as 
bright as this are very rare.

The star, on the edge of the beautiful 'Beehive Cluster', aka 'Praesepe', or 
M44, is a Delta Scuti type variable, but with a tiny amplitude of only 0.01 
magnitude. The spectrum is A7, so it's quite white, and while it may not 
contrast strongly with the rings, it should show up nicely against the warm dusky 
tint of Saturn's South Polar region.

The event will all be visible from Ireland, although Saturn is a bit low down 
at the start. The following times are from my Skymap Pro, for Ireland, but 
are only approximate: more accurate times will be available later.

Disappearance at outer edge of rings, about 18.45
Reappears in Encke Divison, about 18.58
Disappears behind globe, still behind rings, about 20.05 (I had to estimate 
that, as it was shown 'hidden' behind rings)
Reappears near S Pole of globe, about 20.48 - very hard to estimate that, as 
it comes out at a very shallow angle.
   More accurate times, position angles, etc will be given later, but that 
gives you some idea what to expect

This is a chance for all you observers with good equatorial or altazimuth 
driven telescopes and CCD cameras, or even digital video cameras, to do some 
worthwhile astronomy! But for everyone, it will be a very interesting event to 
watch, seeing the star wink in and out as it crosses behind the rings. So mark 
your diaries now. 

And as a finale for the event, Saturn will skim through the Southern edge of 
the Beehive cluster over the next week or so after the event. In fact, it will 
also occult two much fainter stars: mag 12.2 on 28 January, and mag 12.4 on 
30 January, but these will be much more difficult to observe.

Clear skies,

Terry Moseley

Last Revised: 2005 May 3rd WWW contact:webmaster@arm.ac.uk

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