I took some more images on October 2nd, with the moon nearly full and so less-than-dark skies. Using the Celestron wedge I was able to get 2-minute exposures. The wedge still offers no guarantee that the tracking will be perfect nor be free from other inaccuracies. But I did get some decent images and the tracking is good enough that field rotation is no longer a problem. Further practice and “drift alignments” could produce better results in the future.
Here’s the latest Dumbbell Nebula photo after processing and with 2×2 binning, followed by the September 26th image for comparison: