Sunday, 18 January 2009

Lacrosse 3 and Uranus

This evening it unexpectedly cleared. I photographed the only available pass of Lacrosse 3 (97-064A) to clearify whether it was still on-time. It was: I obtained two points with delta t resp. 0.03 and -0.08s and delta positions 0.019 and 0.039 degree respectively.

The pass was a very low pass however, the satellite did not come higher than 25 degrees in the sky. This made it difficult, and I only managed to capture it on two images when the satellite was just above rooftop level, in a "gap" between two roofs. On the first image it appears from behind the roof (endpoint measurable), on the second it disappears behind the roof (startpoint measurable).

When astrometrically measuring the images, I noted a relatively bright star near the end of the trail that I could not identify. It was also on the 2nd image. The star was bright enough that it should appear in the database AstroRecord uses, and my Sky Atlas didn't show a star there either. So...?

As I was measuring the image anyway, I decided to measure the star to get a position for it. it yielded (18 Jan 2009, 17:49:12.3 UTC):

RA 350.855, dec -4.751
= 23h 23m 25.2s, -4 45' 03.6" (2000.0)

I checked AstPlot: it did not show a star nor an asteroid on that position. I downloaded a NEAT image of the region: again, no star on that position....

By that time, I was thinking: Oi, what's this?!? A nova?!?

Then I got a hunch. I started up MICA, and obtained accurate positions for Uranus and Neptune. And yes, there it was:

Astrometric Positions Mean Equator and Equinox of J2000.0

Date Time RA Declination
h m s h m s ° ' "
2009 Jan 18 17:49:12.3 23 23 24.115 - 4 45 03.16

So, I accidently "re-discovered" Uranus... 228 years too late... :-p

A reduced resolution crop from one of the images is below, with objects annotated:

(click image to enlarge)


ericswan said...

I don't mean to be dull about such things but why point your telescope at the roof? You should be up there doing your work.

Station operator SatTrackCam Leiden said...

Very simple answer: the roof is not accessible to me. So I am stuck to the common courtyard of the housing complex where I live. Either that, or move to a completely other spot (which I have, but as it involves a distance biking I only visit it for very special occasions)