MDM Trouble Report for 2015 Dec 15

Telescope: 2.4m
Observer(s): Douglas, Nunez (Columbia)
Instrument: ModSpec/Echelle

Problem(s) Encountered:

At one point in the evening (0145 local/0745 UT) we found a guide 
star and set up the autoguider, but within 30 seconds the guider 
started moving the telescope by 10-20 arcseconds at a time, even 
though we could see the guide star clearly in the guide camera 
box (briefly, until it lost itself). It basically moved in larger 
and larger circles until we stopped auto-guiding. 
We tried changing guide stars, and the problem repeated. 
We guided by hand for that target, but didn't encounter the 
problem again. 

When we were closing up, one mirror cover (the one farthest from 
the garage door when the telescope is at zenith) did not close. 
We had turned the drives switch off shortly after hitting the 
mirror cover switch, if that might have had any effect. 
We solved the problem by swtiching the mirror cover switch to 
open again (which did not actually open any additional petals) 
waiting a bit, then flipping it back to closed again. Then the 
one petal finally closed itself. 

-----
In the middle of a long observation around 0500 UT/2200 local, 
as the dome was rotating towards Az=10 degrees (moving in 
decreasing Az) we heard a loud sound like a door slamming. It 
was not either of us. We couldn't find anything visibly wrong 
with the telescope, and all the readings were normal. So we 
finished our exposure, shut off the auto dome, sent the 
telescope to zenith and closed mirror covers (the humidity has 
also been dancing around, so we didn't want to worry about that
too) and inspected the dome for any problems. 

We initially suspected that the dropout ran into something. We 
made sure the dome could still rotate, brought it home with no 
further noises, and closed the dropout. We couldn't see anything 
wrong. Maybe the dropout ran into some ice on the roof, but we 
didn't see any ice or water on it. 

We re-opened and kept observing. I feel a bit strange for 
filling out a trouble report for things that go bump in the 
night, but better safe than sorry, so here you go.

UPDATE at end of night; this repeated once more, and we think 
it was one of the doors between the control room and dome that
didn't close all the way, and then was shaken into closing 
properly as the dome rotated. 

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

Submitted on 2015 Dec 16 [6:27:02]
NOTE: This trouble report replaces the previous report for 2015 Dec 15