Date: Sun, 28 Jun 1998 06:57:10 -0600
From: long@apo.nmsu.edu (Dan Long)
Subject: 2.5m night report 980627
                          SATURDAY JUNE 27, 1998
                     APACHE POINT OBSERVATORY SDSS 2.5m
                              OBSERVING  LOG
   The enclosure was opened up shortly before 19:00 and the fan turned on.
It was rolled off at about 20:00.
   The last night of this dark run was clear all night with reasonably good
seeing, as it has been for most nights of the run.  Best fwhm was around
1.0 arcseconds with 1.1 to 1.2 typical.
   Charlie Briegel gave us the option of using the integrator term for
running the axes.  Unfortunately when the integrator term was used in
azimuth an approximately 10Hz vibration began when moving in either
direction at about 9000 counts per second.  Once started the oscillation
continued until "s" was pushed for the azimuth.  Neither "h" nor any other
change in velocity would get rid of it.  We decided to revert to the
standard coefficients for both axes for the night's run.
   As the mcp was not rebooted today and the telescope was not moved, we
had a long baseline to check encoder drift.  The values at the time the
telescope was parked at the end of last night and when we started tonight
was only a few arcseconds in each axis.  In fact we did not have to rezero
any of the axis positions ( though we did check them against the reference
marks ).
   As with the past few nights, we parked on the equator two hours west.
Strip data was taken from about 22:00 to 01:30.  An offset was made to
attempt to fill in the stripe, but it appears we may have missed the
desired declination change by about 3 arcminutes.  This is most likely from
telling the telescope to move to the wrong Az,Alt due to incorrect
calculations, rather than the telescope not moving the requested amount.
   From 1:30 to 2:00 a focus sweep was done.  The out of focus donuts were
noticed to be somewhat comatic, so the primary position was adjusted.
Prior to the change the coefficients were.  This took from 2:00 to 3:30.
Galil:  7050, -4950, -700, 20400, 7400, 7400
Setmir:  Not recorded.
After the changes they became
Galil:  7490, -6256, 169, 26816, 41289, 41287
Setmir:  0, -43.9, 28.3, 1550, 2400
At this time the secondary values were
Setmir:  830, -198.5, -34.6, -56, 205 ( nominal 2hrs over values )
The remainder of the night was spent collecting Hartmann data on the meridian.
   During twilight the Hartmann screen was removed and the camera taken off
the telescope.  All went smoothly putting the camera away.
   Unfortunately dewar 6 is having a hard time staying cold.  In fact it is
warming significantly ( more than 10 degrees above its limit  and
increasing ).  Thus the decision to keep it cold for Mamoru was changed and
the camera is being allowed to go warm.
   The telescope was closed up shortly after 6 AM after a very successful
dark run.
  For the site staff:  It is pinned at stow position.  Az and Alt brakes
are on.  The turnbuckle connecting the PSS and the windscreen is in place.
The telescope is slightly front heavy, so you will probably want to move
the altitude manually with the windscreen in this configuration.
                                Dan