Monday, 7 January 2008

USA 193, first ETX observations of NOSS 3-4, and comet 17P/Holmes

Last two nights (the evenings of 2008 Jan 5 and 6) were the first nights I tried to do visual position determinations on fainter satellites. Targets were the NOSS 3-4 A & C pair (07-027A & 07-027C).

The Meade ETX-70 (see picture below), a small and compact 7 cm/f 350 mm (F5) rich-field refractor, turns out to be a very nice instrument for satellite observing. It was cool to see 07-027A sail majestically in and out of the FOV, half a minute later followed by 07-027C. At 14x magnification with the 25 mm eyepiece, the FOV is over 3 degrees with (from the light-polluted mid-town location Cospar 4353 in Leiden center) a limiting magnitude at mag. +9.5.

(click image to enlarge)

The Meade ETX-70. Attached is a home-made piggyback mount for my camera

I had some problems operating my (new too) stopwatch though. During the Jan 5 attempt, I pushed a wrong button when I wanted to read out the memory, resulting in the loss of all 4 points. During the Jan 6 attempt, I did the same with 2 points on 07-027A after I had succesfully retrieved 2 points on 07-027C (plus another point on the same object taken during an earlier pass). Evidently, I still need some practise. Logging with the stopwatch, estimating the fraction between two stars crossed, and operating Ted's Obsreduce software all went surprisingly well though.

On Jan 5th in deep twilight I observed USA 193 (06-057A) zipping by. I got two camera points on it but apparently the times are off. This failed (?) reco sat keeps being a fine object to view as it is bright and very fast. If it's orbit continues to decay as it does now, the object will end its life around the first week of April.

On Jan 6th I observed, apart from the NOSS 3-4 pair, also Lacrosse 2 & 3.

The evening of January 6th was very clear, and I used the ETX-70 to function as guiding mount for the Canon Ixus camera. Target: comet 17P/Holmes.

The comet has grown very large (about 1.12 degree currently) and vey diffuse. Below is a photograph showing the comet which is a stack of 39 images of 15 second exposure each. The open cluster in top of the image is M34, the bright star below the comet is Algol. Because the ETX-70 is on an alt-azimuth mount and the comet was near the zenith, where the effect is largest, some field rotation is visible in the stars near the image edges.

(click image to enlarge)

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