Problem(s) Encountered:

I noticed today that the rotator angle is systematically offset by about -1.5 degrees (i.e. I had to add +1.2-2.3 degrees to get it about right). Previously I had thought it was a problem with the angles in my object list, but comparison with ds9 showed a consistent offset. Although the seeing is good, the actual offset is hard to measure without a dedicated effort; I am not sure if it is a constant offset. I went back and verified that this issue was in the first image I took, so it preceded my run.

The website instructions say not to play with the rotator encoder without consulting staff, so I merely accounted for it in the remainder of my observations.

Solutions:

Rotator was off by 1.6.  I carefully aligned the rotator to zero.  This is done by raising the platform and peeking in above the rotator on the north side.  There are a roller and detent (remnants of the old rotator system) that, when the roller is in the detent, indicate that the positioning is zeroed.  With the system reset to proper alignment I ran the rotator through paces and noticed no error accumulating.