MDM Trouble Report for 2017 Jan 18

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

Problem(s) Encountered:
The hour angle motion and east-west coordinate readout is 
showing some serious-looking symptoms - I'm wondering whether 
yesterday's adjustments had some unintended consequences.  

The telescope will occasionally stop tracking altogether, though
the drive keeps trying -- it's as if the motion jams up.  This 
happened three times.  Also, the pointing drifts relatively
quickly, necessitating a coordinate reset with nearly every 
slew.  The error appears to be entirely along east-west.  As the 
telescope guides on an object -- so its true RA is really 
constant -- the indicated RA creeps upward at the rate of 
something like 20 seconds of time per hour.  

There's also a fair amount of squealing, and they don't sound
like squeals of delight.  The last time the telescope jammed,
I heard a short, rhythmic chirp coming from the dome that 
sounded for all the world like some kind of alarm.  I went out
to investigate and found the RA drive pushing, then slipping,
then pushing, then slipping -- didn't look good!  

One possibility that occurred to me was that one of the 
support rollers on the main drive is going, but when that 
happened before the failure was more gradual -- the telescope
developed a rhythmic slip/recover motion that would last for
several minutes and occur at random, and which grew steadily
worse over several months.  The present symptoms weren't 
happening at all the previous nights -- in fact, the 
pointing was pretty good.



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Submitted on 2017 Jan 19 [3:01:32]