MDM Observatory 1.3m Telescope Observing Report for 2011 Aug 25

Observer(s): Jules Halpern
Institution(s): Columbia U.

Instrument: R4k

Worked for 8.5 hours (most of the night)
Conditions were Photometric most of the night.
Problems were encountered, see the separate trouble report for details.

Seeing and Weather:
   Beg: Overcast, Winds Light & Variable
   Mid: Patchy Clouds, Winds Light & Variable
   End: Cirrus, Winds Light & Variable

Observing Summary:

Telessope tracking and guiding worked very well.
I'm still trying to optimize the parameters for these
functions, but it won't make much of a difference since
they are already pretty good.  Focusing worked well with 
the temporary ./burst script.

However, all of these improvements revealed a new problem,
which I had suspected but only now is clear.  Images are often
double, separated by about 2 arcseconds in the EW direction.
This happened when slewing to a new target.  It is clear 
that this is not a tracking or guiding effect, since it is
seen in brief, unguided exposures.  At first thinking
it was bad focus, similar to the familiar astigmatism of 
this telescope, I tried to focus over and over again,
until it became clear that focus was not the cause.
It can go away after an hour or two.  It has the feel
of a mirror support problem, as if something is getting stuck,
and eventually frees itself.  What I don't know is which
mirror is responsible, and what fixes it (for example,
a large motion of the secondary motor).  So far, about
half of ny data is affected.  It's always the same magnitude
and direction of displacement.

At the end of the night, a standard star that I observed
clearly shows this effect.  If anyone is interested in
seeing such an image I can send one.  (It's displayed on
the ds9 here.)

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Submitted on 2011 Aug 26 [6:08:48]