At about 21:30 the light clouds parted and the stars were bright against a really dark backdrop, so I took advantage of this unpredicted opportunity and set up to get some more experience of webcamming Saturn with the scope. As expected, the seeing was rubbish again (too much air-turbulence caused by rising warm air mixing with the colder stuff higher up), so the images in the acquired .avi files weren't holding shape or focus. To get some idea of the seeing, here's a 15-second snip from one of the .avi files, in .mp4 format:
Anyway, I ended up with 9000+ frames to play with. I plugged the files into K3CCDTools to do a quality analysis, then exported the best 10% + about another 100 that the quality sorter ignored to a folder, manually sorted the best 360 of these in vdub and then stacked 'em in Registax, which didn't crash at all this time! The result's not brilliant, but it's better than previous efforts: