Problem(s) Encountered:

the dome lost its positioning and tracking.  The positioning issue may be due to observer error in accidentally reseting the dome encoders

We stowed telescope, turned off auto dome and tracking, and manually moved the dome to home position. Then reset the dome encoders and started everything back up.

This solved the position issue, but not the tracking. Dome would not adjust position during long exposures.

We continued to move it manually so that we could take data while trying

to troubleshoot.  This didn''t last very long as bad weather moved in before we had the chance to find a solution.

Solutions:

Verified that the problem existed—when the telescope was slewed to a position via the TCS GUI, the dome would follow correctly.  But then as the telescope tracked, error built up (>7.1 degrees) without the dome correcting.  I then moved the telescope manually, using the hand paddle.  The dome followed accordingly once again.  This time however, the dome corrected for the accumulating error while the telescope was left tracking.  Did this a couple more times to verify what I was seeing.  Indeed, as long as the telescope was moved manually, the dome would move, and track, correctly.  If the telescope was moved via the GUI, the dome would fail to track.  I know this is a “huh?!” moment, but it’s what I saw.

Power-cycled the dome controller box in the computer room and restarted the TCS GUI.  After this, several tests, both yesterday and today, and the dome appears to be functioning normally.  We will watch for this to occur again while on-sky, weather permitting.