I opened up the big dome at around 21:30, got plate solving to work successfully, did a manual meridian flip without incident although plate solving would not center on the target, I think that I know the solution now though. 100% cloud cover in a short space of time stopped me at around 03:30 so I packed everything away, then on the way to the car at 04:00 it was totally clear again. I tried to find the 21P Giacobani/Zinner Comet visually but did not locate it. Observed M42 and a few other targets and left at 04:45, when it had clouded over again.
Jonathan