This is an odd problem that had occurred about a month ago, and I just thought it was a fluke, but then occurred again last night. I’m using SGPpro 18.104.22.1683 with a EdgeHD11 on a AP-1100 GTO mount. Guiding via PHD and OAG. I had set a sequence to capture M90 with 20 RGB subs followed by 40 Lum. Weather was not great, there were some clouds which did require SGP to go into recovery mode a few times, but when the problem occurred the skies appeared to be clear.
All the RGB subs showed great guiding - typically no more than 0.5 to 1.0 arc-sec (not bad for the sky conditions. Then, when the Lum subs started each image started drifting in RA about 1.8 arc-sec per sub (120sec exposure). DEC was spot on.
The Lum Sequence started at 00:45 on 5/14/2021 and ended at 03:02. (Complete sequence started at 22:09 on 5/13 and ended at 04:29 on the 14th.
Guide cam ZWO174mm; AP software APCC using the APPM Model for tracking and guiding corrections; Stellarium and Stellarium Scope for pointing.
I’m at a loss to figure this out, as it could be SGP, PHD or even the AP software, though that is unlikely as I’ve demonstrated almost 2 min subs unguided (but you never know).
I’ve pasted links to both the SPG and PHD logs as well as the seq file at the end of this message. I will also post this to the PHD forum as well.