MDM Trouble Report for 2009 Mar 10

Telescope: 2.4m
Observer(s): John Thorstensen (Dartmouth)
Instrument: echelle CCD + Buckeye FW

Problem(s) Encountered:

The HA encoder intermittently stops counting.
  
I first noticed this when I was dead-on a target (and tracking) 
and noticed that the RA was registering something like 30 sec 
high.  A couple hours later, I caught it in the act -- as I was 
tracking on a guide star (no question that the telescope was 
tracking normally) the RA indicator started counting upward at 
about 1 sec per sec.  I didn't have the presence of mind to 
notice if the HA indicator was holding steady, but I bet it 
was.  The problem persisted for about a minute, which obviously
threw the pointing way off.  

The problem occurred twice near the beginning of the night, but
then did not recur.  If this is the typical failure rate it will
be nearly impossible to diagnose, unless there's something 
obviously wrong. 

I also lost pointing once on the previous night, but
at that time I figured I'd just made some mistake (easy to 
do so when you're dodging clouds and improvising).  But I
couldn't figure out just what mistake I'd made, so I bet that
was actually the beginning of this problem.



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Submitted on 2009 Mar 11 [6:46:45]