Monday, January 11, 2016 3:15 PM

Problem(s) Encountered:

The old problem that we have diagnosed as a probable motion of the MIS guide probe mirror is recurring.  It is manifest as a diagonal jump in the image by about 4 arcseconds.  Tonight, it occurred three times in a span of 2.5 hours.  In addition, there is a slow drift of the image in the same direction, but perhaps less than in previous years.  Following discussions with Eric and Mark Wagner last summer, it seems that this can''t be fixed without a major redesign of the guide probe mechanism.


This problem, if it is indeed the same problem, has taken on a new twist as far as I understand.  “Flop” appears to be a misnomer as what was seen is a progression in one direction, occurring three times over the course of observing a single object (telescope was not set to a different object in between the reported occurrences).  So from seeing the images, the telescope “flopped” in a non-cardinal direction by roughly 4” during a 5 minute exposure.  This was at a positive declination, about an hour east of the meridian.  Then again, about 20 minutes east of the meridian, the same “flop”, in the same direction occurred again.  Finally, at about an hour west of the meridian, a third “flop”, again in the same direction occurred once more.  Thusly, this seems less like a flop to me and more like a steady, somewhat quantized translation.  A flop would be more of a gravity-vector issue where something sets between two states.  This is not the case here.  Not sure yet what to make of this but I’m giving it some thought.