Last night (five minutes after I went to sleep! dang!) the connection to the mount was lost, and SGP seems to have hung. When I found it this morning, though, the mount was still connected, and was still tracking, although of course pointing at the ground by this time. The SGP log, PHD2 debug and guide logs, and a mysterious .wer file found in a folder tellingly named AppCrash_ASCOM.Celestron are all here:
Everything went okay until 11:47:27, when PHD2 seemed to stop responding to SGP, and guiding stopped. SGP 220.127.116.11, PHD2.5. I know there’s some new PHD2 functionality in newer SGP betas so I’ll update, but I wondered if anyone knows if that was really the problem.