Re: LASER BEAM OBS?
Bart De Pontieu (BDP@MPE.MPE-GARCHING.MPG.DE)
Tue, 31 Jan 1995 22:17:40 +0100 (CET)
Bjoern Gimle wrote in seesat/95 :
>Trying to find matching satellite tracks with SkyMap it is obvious,
>like Mike McCants and others fitting orbits to the data have noted,
>that all points do not agree well with predictions.
>Like Mike suggested, the second point could be decl. +3 instead of -3,
>but it seems even better to lower the first obs. to below (or within)
>Corvus instead of below it.
I finally got a hold of the observer on the phone and I have some new
facts/tidbits.
First of all, we should forget the positions I gave you except for the
first one (around RA 12h15m Dec. -11 degrees). The others were not
accurate at all and just for illustrative purposes (something that was
not made clear to me :-(
The correct positions are :
first sighted just above Corvus (RA 12h15m, Decl. -11 degrees)
moved in the direction of alpha Umi (*very* approximate direction, since
that part of the sky wasn't visible to the observer, obscured as it was
by an apartment building) or rather just 'direction north'.
Reached a height of about 60 degrees. The observer reached for his camera
after 15 seconds (trying to fit a fish-eye lens to it), but by the time
he had finished doing that, the satellite had disappeared behind the
building. That is the reason for the low accuracy in position and time of
the pass (and no photo either, unfortunately :-(
The azimuth of the point at the horizon where the laser beam seemed to
originate from was about the azimuth of the first point of the satellite
(in Corvus).
The beam was not infinitely sharp, had a certain width, which was very
small though. Magnitude of the beam was magnitude about magnitude 3. The
satellite was magnitude 1 to 2.
>>Is it possible to have a second by the observer, or the observer/
>>contributor recheck notes for typing errors ?
No typing errors, I was just misled by the very accurate map the observer
sent me. It turns out it wasn't meant all that accurate anyway. I apologize
to anyone having put time into trying to identify this object. Maybe the
wider margins position- and timewise will allow for an identification of
the satellite.
Practically speaking : the first point is very much certain, the direction
'going north/Polaris' is not accurate to within 10 degrees, and the total
duration of the pass (as he saw it) was probably more around 2 minutes than
1 minute. I now think he lost the satellite out of view when it was about
due East. I'm sure this lower angular velocity leads to more credible
heights.
Bart