From: TerryMosel@aol.com
Date: Sun, 9 Feb 2003 15:51:45 EST
Subject: Last days of NEAT, MutJupSat

Hi all,

Comet NEAT is brightening & developing nicely, but is also plunging rapidly 
into the evening twilight. And the Moon is brightening....

So grab a look in the next day or two for the best views.

I estimated it at magnitude 4 at 18.50 this evening, with a 2 degree tail, 
using 30x80 binocs. Prof Mark Bailey (Armagh Observatory) independently came 
up with exactly the same assessment, observing with 20x80s from Oxford Island 
(S Shore of Lough Neagh). Tolis Christou, observing from light-polluted 
Armagh thought it only slightly fainter. And John McConnell (Maghaberry) 
agreed on the magnitude, but saw only 1.5 dgrees of tail with 10x50s.

It can be found for the next day or two by continuing the line down thru the 
diagonal of the Square of Perseus for its own length or a little more; after 
that the distance below the bottom corner of the Square increases rapidly as 
it nears perihelion. If you see it after St Valentine's day, at about 
magnitude 1-2, you'll be very lucky, unless it brightens much more than 
predicted!

Mutual Jupiter satellite event tonight: At 00.51 on 10 Feb (or 24.51 
tonight!), the innermost Jovian Moon, Io, will totally occult (or pass in 
front of) the second one, Europa. The total phase of the occultation lasts 
for only 9 secs, but the partial phases will obviously take longer. Unless 
you have a humongous telecope, and excellent seeing, you can't observe the 
detail of the event, but any small/medium sized instrument will show them 
approaching, merging, and then separating again. 

And you can observe the effect of the occultation by looking for the drop in 
brightness as Io cuts off the light from Europa. Just before the actual 
occultation starts you'll be seeing the combined light from both satellites: 
Io mag 5.0, and Europa, mag 5.3, give a combined mag of 4.4. During the total 
phase this will drop back to that of Io alone, i.e. 5.0. Try comparing the 
brightness with that of Ganymede, mag 4.6, the moon closest to the occulting 
pair.
At the time of the occultation, the view from left to right in a normal 
inverted telescope image will be: Callisto, Ganymede, Io+Europa, Jupiter.

At the time of writing the sky is 100% clear, so good luck!

(I also saw the ISS, and two nice Iridium flares, earlier, so it could be a 
good night!)

Terry Moseley

Last Revised: 2003 February 10th WWW contact: webmaster@star.arm.ac.uk

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