MDM Trouble Report for 2005 May 15

Telescope: 1.3m
Observer(s): patterson, armstrong (columbia)
Instrument: templeton/direct

Problem(s) Encountered:
All right, here's the story:

Images are in:
eve/n08/vir-trouble/

Took flats/biases at HA -2 hours  (+31 57.)  They're all fine.

Slewed to:  12 38 17.5  -03 40 2    (where the trouble was 
   last night)
HA: -00:51:53
UT: 03:41:20

15-s BG38 image - shows these 'dots' again.  See:
  ccd.bg-1.fits
  ccd.bg-2.fits
  ccd.bg-3.fits

So I followed Bob's directions, should this occur again:

1. Immediately moved to 'clear' (no filter.)  Took 15-s image.
   ccd.clear-1.fits --> SAME DOTS.
2. Turned flat lamp on; moved finder mirror in --> took some
   flats.  
   ccd.flat-u-1.fits  --> NO DOTS
   ccd.flat-b-1.fits  --> DOTS?  Not sure.  Exposure too short
       to tell.
   ccd.flat-bg-1.fits --> DOTS?  Not sure.

3. Took bias:
   ccd.bias.fits -->  No dots.  Looks normal.   

4.  Took full (unbinned) BG38 image:
   ccd.bg-full-frame.fits --> DOTS.

Went ahead and observed anyway, in BG38.  ALL our images have
dots.

~ 3 hours later, slewed to 15 58 -00 -9 --> NO DOTS.

This seems to be a problem of inclination angle of the telescope.
The Jupiter suggestion can explain some large bright 'doughnuts' we've
been seeing, but not these dots.  The dots are not HA-dependent; 
they remain basically the same throughout the run's duration.

Also - that strange dark patch on the guider screen reappeared 
(the same thing I showed Bob a couple days ago.)  It
didn't get in our way, but in case it's related, I thought I'd 
mention it.  It was a blurry rectangular shadow, on the bottom
left of the guider screen, at:
12 38 16.5  -03 40 7
HA  -1 2 37
Guider coordinates:  x=5000, y=7000
Initially, moving the guider camera did NOT make this shadow move.
Then, after doing a focus run, I suddenly noticed it was gone.  And
I couldn't find it again.

------------------------------

Submitted on 2005 May 15 [0:39:59]