If that is your first go, then full credits, 1 for getting an image to stack to start with, 2 for working out how to use Registax and three punishing yourself buy trying it with a dob.
There is a bit of black magic to using Registax. I don't think there are two people anywhere in the world that use it the same way. If you haven't read it already, I would suggest having a read of Mikes planetary image processing how to, if only for the Registax stacking part.