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.

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)