Date: Tue, 23 Jun 1998 05:55:32 -0600
From: long@apo.nmsu.edu (Dan Long)
Subject: 2.5m night report 980622
                           MONDAY JUNE 22, 1998
                     APACHE POINT OBSERVATORY SDSS 2.5m
                              OBSERVING  LOG
     The enclosure was opened at 20:00.  The weather was clear and remained
  so all night.  Collimation work continued until about 21:30.  The
  telescope was moved into position for scanning along the equator
  at the meridian.  A couple problems were encountered in doing this.
     The first problem was that the windscreen would not follow the telescope
  in azimuth for any but the slowest speeds.  The number 1 motor would start
  spinning and the others would remain still and the windscreen would not
  move.  Some sleuthing by Pat Waddell turned up that the way the motors act
  when in the servo mode ends up with only the first motor being driven with
  more current as the demand increases.  When run in manual mode, all three
  motors appear to share the load equally.  This is how we moved the
  telescope in azimuth.
     The second problem was that the telescope was found to be quite out
  of balance ( ~50 lb ) front to back in altitude when near the zenith.
  This was traced to a lack of counterweight cover on the on one of the
  front counterweights.  Once in place the telescope moved smoothly even
  holding its position in altitude to within a few arcseconds without
  the brake.
     The telescope was in place and ready to run by about 22:30.  Much of
  the night was spent getting the mirrors properly aligned to achieve the
  best images.  See Brian Yanny's log for details of positions.  The last
  portion of the night was spent taking some frames for working with focus
  via astrometric chips.
     Another thing I noticed tonight was that the sound proofing insulation
  around the MG set sticks out far enough to catch on the pier when moving
  in azimuth.  It scrapes hard enough that the screw holding it on have
  chipped the paint on the corners of the pier in spots.
     The telescope was closed around 05:00.
                                Dan