Date: Sun, 18 Oct 1998 18:23:31 -0600
From: long@apo.nmsu.edu (Dan Long)
Subject: 2.5m obslog 981017
                        SATURDAY OCTOBER 17, 1998
                     APACHE POINT OBSERVATORY SDSS 2.5m
                              OBSERVING  LOG
   The enclosure was rolled off at 18:20 to clear skies.  Skies were clear
all night.  However brisk easterly winds kept seeing between 2.2 and 2.5
arcseconds the entire night.
   With such poor seeing, not much could be determined about collimation.
We started with the same settings for the primary that Pat and I found to
work earlier in the week.  We reduced the y-tilt by 20 arcseconds to get
the best looking images we could.  We could not tell however, what if any
focal plane tilt there was, since focus was such an ill defined parameter
tonight.
   The primary settings we used were
        0 -26.3 10.7 1675 350
   which correspond in galil terms to
        6350 -4650 -250 -5700 44400 44400
   There were a couple of problems tonight.  First, when we installed the
new thicker shim and remounted the camera, the latch below the kinematic
where the shim was placed would not engage.  When we replaced the shim with
the thinner one used last run, all latches operated properly.
   The second problem was when driving the azimuth axis at greater than
80000 counts/sec  a loud hum would start, and would cause the entire
telescope to vibrate.  This was coming from the telescope, not the
windscreen.  Stopping motion and restarting at a slower speed would keep
the hum from returning.
   The telescope was closed at 04:45 after exhausting all items which could
be accomplished in such terrible seeing.
                                Dan