Date: Sun, 11 Apr 1999 07:19:22 -0600
From: long@apo.nmsu.edu (Dan Long)
Subject: 2.5m obslog 990410 ( MJD 51279 )
                          SATURDAY APRIL 10, 1999
                     APACHE POINT OBSERVATORY SDSS 2.5m
                              OBSERVING  LOG
   The telescope was opened at about 16:00.  Prior to this during the day,
the rotary encoder was put back on the rotator.  Some problem with the tape
encoder was causing instability in the rotator which was alleviated by
returning to the rotary encoder.  The tape is still being used for the
fiducials.  Claudio was working with the rotator until about 20:00, at
which time Charlie took over.
   Connie helped again tonight, by being at the telescope when Charlie was
making slews.  Charlie found and fixed the frame dropping problem the MCP
was having regarding TCC input.  He also reduced the altitude coefficients
to keep it from oscillating.  They now match the azimuth coefficients.
   When I found out the telescope was still open at a little before 02:00,
I decided to go in to relieve Connie and to save French having to come back
in ( Sorry French. I should have called and told you to go back to sleep ).
   Charlie continued working until about 04:00.  When he quit, I decided to
try a few slews from the TCC.  The good news is that the telescope slewed
and tracked in all three axes in response to a TRACK ... FK5 command.  The
bad news is that we experienced some difficulties getting there.  The slew
resulted in the rotator moving to a position of about 120 degrees.  As it
approached that position and tracking speed, it began humming.  In order to
stop the humming I issued an AXIS INIT ROT.  This indeed stopped the
humming.  It also stopped the Azimuth tracking.  Nothing I could do from
the TCC could get azimuth to move again.  I could, however, make the
azimuth move from the Menu.  After exhausting all options I could think of,
I rebooted the MCP.  The azimuth would respond to TCC commands after that.
   Another thing we noticed was that issuing an AXIS STOP during a slew,
did not stop the axes.  In fact neither did an AXIS INIT.  It seems that
there must be a large queue of commands in the MCP waiting to complete
while a slew is going on which want to get finished before the STOP or INIT
are acted on.  A more immediate response to these commmands is needed.
   One other note was that during tracking a slight periodic thump was
noticed in the rotator.  It was at quite a low level and may be due to the
arrival of each new pvt packet from the TCC ( the interval of a few seconds
seemed similar to the TCC update frequency ).
   I hadn't planned to come in tonight, but in the end am quite glad I did.
It was exciting seeing the telescope tracking in all three axes!  A lot of
progress has been made this week on the MCP and servo loops.  Much thanks
goes to Charlie and Claudio for the long hours, and to Connie and French
for their help in supporting the engineering run.
                                    Dan