Date: Thu, 28 May 1998 05:15:44 -0600
From: long@apo.nmsu.edu (Dan Long)
Subject: 2.5m night report 980527
                          WEDNESDAY MAY 27, 1998
                     APACHE POINT OBSERVATORY SDSS 2.5m
                              OBSERVING  LOG
The telescope was opened during the afternoon.  Photographs were taken of
the now whole telescope by the Fermilab photographers around sunset.  We
got on the sky at around 21:00.  A meridian equatorial stripe was started
around astronomical twilight.  Once the telescope was focused we got fwhm
of about 1.2 arcseconds.  As it was clear and moonless all night, much good
data was obtained.  Later in the night we moved west of the meridian about
2 hours and took another scan along the equator in an attempt to fill in
the first stripe partially.
We had a few glitches with the telescope control system.  The altitude
drives seemed to have a hard time with small moves ( a few arcseconds ).
Encoder values would bounce around 2 to 5 arcseconds between updates,
making it hard to pin down small moves.  It was also difficult to maintain
a position with the brake as it is necessary to stop the axis ( which then
begins to drift ), before applying the brake.  Related to brakes, it is
quite inconvenient to have to reset the amplifiers at the base of the
enclosure each time a brake is set and released.  It would be much nicer if
the error condition would clear automatically once the brake was released.
Once tonight the rotator amplifier tripped for no apparent reason.  A reset
cleared it and it moved fine afterwords.
Once tonight the MCP Menu hung.  It stopped giving updates and would not
respond to commands except exit.  After a few exits and "Menu"s it froze
altogether.  I rebooted and it came up and worked fine.
The Az and Alt encoders still run in the opposite direction to what makes
sense.  That is Az would have 0 north and 90 west, and increasing Alt on
the encoders is a lower elevation.
Focus seemed to drift more than it should but we followed it fairly easily.
The telescope was close up at 05:00.  Overall a very productive night.
                                Dan