Problem(s) Encountered:

Multiple exposures were lost due to what seemed like the dewar shifting in position during the exposures. The guider was tracking perfectly fine but the images had double stars. Problem occurred 2 times during the night but then seemed to stop.

Solutions:

These jumps in 1.3m images are a legacy issue going back at least 20 years.  We think they are due to guide probe mirror flops in the MIS.  Once or twice a night is typical.  I saw one a couple of nights ago in data from John T''s run.  If  you were watching the guide camera tracking graph in real time you would probably have seen the jump. (Jules Halpern)