Date: Sat, 21 Nov 1998 07:00:36 -0700
From: "John W. Briggs"
Subject: 2.5m obslog 981120, MJD 51138
Friday, Nov. 20, 1998 (MJD 51138)
Apache Point Observatory SDSS 2.5-m
Observing Log
	Clouds prevented opening of the enclosure until 21:00.  Although
the optical alignment again remained satisfactory, seeing was never good.
We began at 1.3 arcseconds, and it deteriorated to worse than 2 arcsec over
the whole array by 02:00, when winds were out of the north at 10 mph.  High
sky brightness in the red chips was noted for awhile around this time.
	Lupton and Annis ran the camera and pursued various software
engineering tasks, including tuning the focus loop; Briggs operated the
telescope (his first solo with the 2.5-m).  Unlike yesterday, the Galil
controller for the secondary mirror motion worked fine all night.  Lupton
and Annis noticed empty gangs several times, but otherwise things were
generally uneventful, with seeing becoming even worse at the end -- around
3 arcsec.
	The enclosure was shut around 05:30, and a full 180-L dewar was
installed at that time.  The pressure in the nitrogen tank downstairs was
below 400 psi at the end of the night, so Briggs installed a fresh tank,
reading 2000 psi, to play it safe.
	The green light indicating proper telescope azimuth stow position
went out for some reason after the enclosure was closed, but with the
azimuth brake disengaged, Briggs was able to move the telescope in azimuth
slightly by hand, whereupon the light came on, and the telescope was
consequently commanded to its nominal imaging-mode stow alititude of 18
degrees.
				--J. W. Briggs
********************************************************************
John W. Briggs
University of Chicago Engineering Center,
Yerkes Observatory
[Deployed at] Sloan Digital Sky Survey          Voice:  505-437-6822
              Apache Point Observatory          Fax:    505-434-5555
              Sunspot, NM 88349