Twenty-one alignment points in Registax 4 results in one of the sharpest photos I’ve posted. It took three tries: the first try had 22 points, and registax hung on the last one when optimizing. The second try had an access violation when aligning. The third try I quit all other applications and let the program run without interruption.
The image is inclined about forty degrees, so at the top is Posidonius on the border of Mare Serenitatus.
Here’s the very next shot, at f/9. 34 alignment points, but I threw away half the image. This represents about a dozen.