Date: Thu, 24 Sep 1998 04:10:43 -0600
From: long@apo.nmsu.edu (Dan Long)
Subject: 2.5m obslog 980923
                        TUESDAY SEPTEMBER 22, 1998
                     APACHE POINT OBSERVATORY SDSS 2.5m
                              OBSERVING  LOG
   The enclosure was rolled off at 18:30.  The time before astronomical
twilight was used to check modifications done during the day.   The encoder
scale was verfied to be correct.  The fiducial setting feature also worked.
Some changes were made to the soft inhibit position for altitude at zenith
to allow one to back off without having to bypass any interlocks.  It was
tested, and indeed one can simply reverse direction to come away from the
zenith limit.
   At about 20:30 we set up on the equator at the meridian.  The focus loop
was used to bring us in to focus from quite far out.  Early images showed a
fair amount of astigmatism for the latest mirror settings.
                0   -12    9   550   640
This may have been due to the mirror not having yet reached thermal
equilibrium.  Unfortunately we were unable to verify this.  A storm came in
from the southwest and forced us to close at about 21:40.  We had a brief
rain shower at about 22:15.  The rest of the night one or more of the
following kept us from opening, clouds, high winds, and humidity.
   One thing I noticed when I closed was that the windscreen altitude
oscillations when moving down, could be lessened by leaning on the
windscreen weights as it moved down ( essentially making the windscreen
bottom heavy ).  This would seem to point to balance playing a part in the
instability, as the windscreen is currently front heavy.
                                Dan