Date: Sun, 9 May 1999 06:07:45 -0600 (MDT)
From: hayes@apo.nmsu.edu
Subject: 2.5 m obslog 990508 (MJD 51307)
			Saturday May 8, 1999
		Apache Point Observatory SDSS 2.5m
			     Observing Log
Observing Team:
		Jeffrey Hayes (APO)
		Ellyne Kinney (APO)
		Bob Nichol (CMU)
                Matt Newcomb (CMU)
                Aronne Merrelli (CMU)
Weather:  Clear and low dust.  However windy (~20 mph steady and gusts
up to 25 mph.  We opened at 18:00 MDT.
We started to investigate the problem that Dan saw last night with the
15 degree stop not retracting properly but ran into a new problem ourselves.
When we went to put the telescope to the 0.8 degree position to roll the
building off, we found that the MCP would not allow us to do so.  We would
get to within 1/8-inch of the stop when an interlock would kick in and
not allow further motion.  At this point we raised the telescope to
3 degrees and tried to move to the 0.8 degree position again, and again,
we hit a stop.  We noticed that the clinometer and the MCP ALT reading
from the menu were in disagreement by roughly 0.5 degrees.  We speculate
that the MCP may loose track of its fiducial mark, but are at a loss to
explain why this would be the case.
We managed to coax the telescope down to the 0.8 degree position using the
manual paddle, and then opening the building.
We then started to investigate the problem with the 15 degree stop not moving
properly.  We found on the first try while slewing up from the 0.8 degree
position manually that the stop would not come out.  We then checked the
hoses and noted that one faring (connected to a blue hose) was somewhat
looser than the green counterpart, but not so loose so that any leak could
be heard.  We then pushed the stop out by hand so that it was in the "out"
position (i.e. would prevent telescope from moving lower than 15 degrees.)
At this point we execised the 15 degree stop by slewing the telescope
back through the region of interest through 6 cycles (slewing both
up and down).  In each case, the stop either retracted or moved out as
it is expected to do.  It seems unlikely that we have reseated anything, and
we suspect the valve might be a candidate to look at.
One other point to note, the dome for the DIMM is not working.  The chain
that meshes with the crank appears to be very loose and does not fully
engage.  We had to open and close the dome by hand.
The agenda for the evening was to refine the instrument block for
the spectrographs.  After a somewhat rocky start, due to 3 MCP crashes,
the loss of axes once, and 3 run-aways we did manage to centre up on a
couple of stars, and then slew to the K fast field, where we did get stars
down the fibres.  However, we could not seem to get the guider to work
in a reliable fashion.  We had problems getting repeatable offsets to
work so that the guider could be used.
We note that it was very difficult to keep the Red spectrograph cold -- it
would warm up in roughly an hour after being filled with NL2.
This is a problem that will have to be looked at during the day.  There were
no such problems with the Blue side.  We did obtain very decent sky flats which
show a number of sky lines from the Blue spectrograph very nicely.
We also obtained a number of shorter exposure flats.
With the experience we had in putting LN2 in both spectrographs, we would
like to urge that a better way be found for filling them in the short term.
The current method is awkward and could be danagerous as it involves
getting under the telescope with a portable dewar.
We closed at roughly 5:20 MDT.
Jeffrey