Registax n00b

I downloaded Registax 6 today, thought I'd see if I could improve my moon images.

Fell at the first hurdle, really - I tried to stack three images taken within a few minutes of one another at the same focal length, converted to JPG and cropped to the same number of pixels in height and width.

It identified lots of alignment points, but when it superimposed them, they didn't quite line up so the result was rubbish.

I only had a very brief go, so I'm probably doing something wrong.

Any pointers and suggestions gratefully received - including that I should RTFM, but I know that already