Date: Tue, 13 Oct 1998 07:02:42 -0600
From: long@apo.nmsu.edu (Dan Long)
Subject: 2.5m obslog 981012
                          MONDAY OCTOBER 12, 1998
                     APACHE POINT OBSERVATORY SDSS 2.5m
                              OBSERVING  LOG
   The enclosure was rolled off at 18:00 to clear skies.  Claudio Rivetta
and Charlie Briegel ran some tests on the altitude windscreen in an attempt
to characterize and correct oscillation as the telescope moves down in
altitude at rates over 50000 cts/sec.  They collected information but did
not find an obvious fix.
   Pat Waddell and I set up on Polaris at about 19:15.  We spent most of
the night tweaking primary parameters.  After 4 itterations of taking
images, going to zenith, adjusting translation and tilt, then returning to
Polaris, we got very nice looking images.  The appearance after each
itteration was as expected.  The mirror system was behaving in a reasonable
fashion. It's just that special care must be taken when changes are made.
That is all translations must be done at zenith, and the air must be turned
off to the lateral links while the move is made.  Finally, while still at
zenith, several down/setmir cycles with the final setmir going past the
desired piston, then back.  The final parameters for the primary at Polaris
were ( in setmir terms )
             0 -2.7 15.6 850 150
   We then homed the primary and went back to these settings.  Images
looked as they did just prior to the homing, so the actuators had not lost
any position.
   Next we slewed the telescope to the equator on the meridian, and
attempted tracking stars.  We found it was possible to track stars while
they were within about 2 degrees of the meridian.  After that it became too
difficult to keep up with the rate of change in elevation.  The tracking
rate in azimuth was about -1980.  After a few passes on stars we got enough
data to determine slightly different primary parameters were needed at the
equator.  These were
             0 -6.3 19.3 1050 350
Despite imperfect tracking and not knowing exact focus, we managed to get
images around 1.2 arcseconds fwhm while on the equator, and one time we got
a .9 arcsecond image in a 20 second exposure!  Images revealed that
additional tweaking might be warrented.  The data indicated new values of
             0 -7.2 21.1 1150 400
We ran out of night before we could check these numbers.  We will look at
them tomorrow night.  The telescope was closed at 6:45.
                                Dan