MDM Trouble Report for 2005 Aug 27

Telescope: 1.3m
Observer(s): Halpern (Columbia U.)
Instrument: Templeton Direct

Problem(s) Encountered:
Now that I am no longer Director, I have time to think about small
problems that, while they are not vital to the overall functioning
of the observatory, might be satisfying to address, and may even
lead to insight into other, larger problems that might never have
seemed to be related until the reason for both is found.  For as
long as I can remember, observers have mentioned that the 1.3m
telescope  jumps  occasionally, the evidence for this being a
double image, although no one has ever actually seen such motion
on the guide monitor, or in any other way.  Some have felt that
it occurs at a given hour angle, or at a particular time of the
night.  But here's what I noticed.  I have been observing for
four nights, and I have gotten a double image exactly once each
night.  Not at the same position or time or hour angle, but the
fact that it occurs only once is what seems odd.  The double images
are in the same diagonal direction each time, that is, not just
in R.A. or in Decl.  So it is not a guider problem and probably
not a drive motor or gear.  I have been observing fairly 
efficiently, so I started to think: what if this is an event that
happens to the telescope once each night, and you will see it
if you happen to be exposing at the time?  And then I started
to wonder, what is it that could happen only once per night?
Well, for one thing the temperature usually decreases during the
night, and so if there is bi-stable state in some piece of
hardware, with hysteresis, then there will be a sudden
transition at night, and one during the day in the opposite
direction.  Maybe the reason for this effect is related to the
general structural problems with the telescope that makes
focussing and collimation so difficult.  Anyway, it's something
to think about during a long night. . . I would be interesed
to hear if anyone has had a different experience with this
problem.

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Submitted on 2005 Aug 27 [23:42:56]