Later, a check on the series revealed that things were not going well. The alignment was off. Perhaps I had bumped the mount without realizing it. For whatever reason, only the test image turned out halfway decent. The rest had significant star trailing.
I recently took a closer look at the series, salvaged the best ones, and applied a star rounding filter to them. The results weren't spectacular, by any means, but with a little more processing and a few tricks I managed to throw together a wide-angle view of the area around M81/M82:
|Messiers 81 and 82 and friends; ST80 on Vixen SP; 8x180|