Paul
a further point. With my RC8 and the acrylic disk, it can be tricky getting a suitable guide star in sparse fields. Its really not an issue with guiding - rather its calibrating that is the problem. For some reason, Maxim needs a brighter star to calibrate properly - when that is done, it is happy with a dim star to guide on. So I usually calibrate on a bright cluster with plenty of options and then slew to my target.
That said, it might be pilot error. It often is sadly. At least the pilot is finding new errors to make
I'm very happy with mine and would buy another in a heartbeat
Pete