Date: Fri, 23 Apr 1999 05:35:02 -0600
From: long@apo.nmsu.edu (Dan Long)
Subject: 2.5m obslog 990422 ( MJD 51291 )
                         THURSDAY APRIL 22, 1999
                     APACHE POINT OBSERVATORY SDSS 2.5m
                              OBSERVING  LOG
   Here is an excerpt from tonight's forecast.  They definitely got it
right tonight, though I think this is the first time I have ever seen the
phrase "fair and dusty" used in a forecast.
        ...WIND ADVISORY THROUGH 900 PM...
        .TONIGHT...FAIR AND DUSTY. SOUTHWEST WINDS 25-35 MPH...
   As you might have guessed from such a forecast we did not open tonight.
We did some testing of telescope motion by tracking limited ranges inside
the dome.  By using the convert feature of the TCC we could have it
actually track the sky starting at the current telescope position.
        CONVERT  Current_Az,Current_Alt OBS FK5
Then track at the decimal degree RA and Dec it returns.
        TRACK RA,Dec   FK5
   Needless to say an alarming number of interlocks needed to be bypassed
to do this.  What we did was to bypass all inerlocks to do with the 15
degree stop, and the air supply to the stop was disconnected with it
retracted.  We also had to bypass the azimuth stow position switches.   We
enabled the azimuth motor directional permits, and the windscreen azimuth
permit.  We used a couple of the 44 lb weights put at strategic places on
either side of the doghouse to limit azimuth motion via the paddles.  The
list of overridden interlocks follows.
        Slot 4  Ch 1    Az_Mtr_CW
        Slot 4  Ch 2    Az_Mtr_CCW
        Slot 4  Ch 6    Wind_Az_Mtr_Permit
        Slot 6  Ch 5    15 Deg Stop In Permit
        Slot 6  Ch 6    15 Deg Stop In
        Slot 6  Ch 7    15 Deg Stop Out Permit
        Slot 7  Ch 7    15 Deg Stop Out
        Slot 9  Ch 0    Az_Inst_Chg_A
        Slot 9  Ch 1    Az_Inst_Chg_B
   It would be nice to add this logic of having either stow switch being on
to be a valid inside the enclosure azimuth position.  It would make stowing
the telescope easier, and could also be used to allow limited azimuth
motion within the building without having to override any interlocks.  Some
adjustment of dog lengths might be needed to insure that the telescope
makes it by the doors, but I think it would be very useful to implement.
   I noticed when we overrode building clear az, it also gave the OK in
altitude.  I take this to mean that the 19 degree upper limit would no
longer hold?  Also I probably didn't need to override all 15 deg stop
interlocks, but this did work.
   This setup worked well, and with someone at a stop button at all times,
I think it is also relatively safe.  I will say, I think it would be safer
if we wouldn't have had to use the az motor permit switches, and could have
simply used the azimuth stow switches for the allowed range.  Comments and
suggestions from the interlocks crew at Fermilab on all this would be
welcome.
                                  Dan