The February Sky & Telescope
magazine has an article and basic tutorial on a new 'free' image alignment and stacking program.........AviStack
The program is very similar to Registax, but the auther feels that AviStack does a better job on closeups of the moon. Generally, closeups of the moon fill the entire frame with craters, rille's, mountains, etc. Often, Registax has a difficult time aligning these almost infinite number of features.
AviStack produces a huge number of alignment points across the entire image. For fun, I took an older video that I had previously processed in Registax, and reproceesed it in AviStack.
* The auther continues to favor Registax for planetary images. Planets are much smaller and seldon if ever fill the frame.....in most cases the planet itself covers less then 10% of the frame area. Multiple alignment points are seldom needed.
You be the judge......the original Registax processing versus the image processed in AviStack.
This was not a great raw video, and the differences are subtle, but I think you can see that the detail and clarity is a bit more evenly spread across the AviStack image.