Date: Thu, 3 Jun 1999 06:51:05 -0600
From: long@apo.nmsu.edu (Dan Long)
Subject: 2.5m obslog 990602 ( MJD 51332 )
                         WEDNESDAY JUNE 2, 1999
                     APACHE POINT OBSERVATORY SDSS 2.5m
                              OBSERVING  LOG
    Observering team:   Dan Long                (APO)
                        Jeff Hayes              (APO)
                        Ellyne Kinney           (APO)
   Tonight opening was delayed until 23:30 by dust.  Once open I used the
engineering camera to do a quick test of Charlie Briegel's new mcp code
incorporating DRIFT.  In repeated slews between two FK5 stars, the stars
consistently showed up within a couple pixels of the same location.
   With the rest of the night I took a 70 point model.  A quick fit to the
existing model coefficients resulted in a mediocre 12 arcsecond sky rms.
However a plot of the data showed clear systematics which I hope can be
knocked back by using additional coefficients.
   I mentioned this last night, and I'll do so again.  When the primary is
homed via the relax command, and is near the zenith, there is a definite
scraping sound coming from the back of the PSS which sounds like something
moving against the rough surface of the glass on the side of the primary.
Someone needs to check this to insure that nothing bad is happening/will
happen to the primary.  Until this is checked, I would not recommend
issuing commands which result in large pistoning of the primary.
   Also, out of focus images were quite comatic with the primary at it's
new nominal position of
   setmir:  0   3.9   -2.3   -128   -214
   galil:   4350 -1750   0 16300  -11550  -11450
The linear gauges in this position were
   1.9325
   0.5560
   0.5575
   0.4220
   1.8845
   0.3840
   The scraping sound combined with the comatic images worried me that
maybe the primary was not where it was supposed to be since it went off air
over the weekend.  I set the primary to the mechanically collimated
position of all zeros and recorded the following mig numbers.
   Tonight      Jim Gunn's from
                earlier in the year
   1.9320               1.9310
   0.5565               0.5570
   0.5580               0.5575
   0.4135               0.4135
   1.8895               1.8895
   0.3890               0.3890
As you can see, the primary mirror does appear to be in the proper place.
Could the now comatic images be due to an error in secondary position?  I
homed the secondary with the following error list
000020000,  000020000,  000010000, -000000500, -000000200 position error
Images looked the same as before the homing.  See
sdsshost:/data/spectro/guider/donut_990602.fits for an example.
   I could not set the rotator fiducial tonight.  It would not find the one
near zero.  In fact in slewing all around, it only managed to find one, and
it was around 162 degrees.  I had no trouble setting it last night.
   I checked that the zero point was reasonable ( it agreed very well with
the inst change mark ), and decided to proceed with the model as time was
running short, though the question raised by the comatic images makes me
wonder how useful this model would be.
   I took a 70 point model using the rotator and with DOPTERRKLUDGE just to
eliminate any question of drift being an issue.  The 12 arcsecond sky rms
using the existing coefficients was higher than I expected.  As I mentioned
above, a quick check of the data showed some definite systematics on the
plots, which I plan to fiddle with during the day Thursday, when I'm a bit
more awake.
   Best focus of the engineering camera ( corrector in place ) was around
-1100 tonight.
   The telescope was closed at 05:45
                                WEATHER
   Weather tonight started mostly cloudy, but cleared by about 22:30.  It
was clear or mostly clear the remainder of the night.  Winds were light
southwesterly, temperatures were 10 to 12 C, the dewpoint depression was
between 10 and 14 C.
                                  Dan