Thanks guys, I didn't even think of the 'background' light pollution! I guess I'll be limited to 5 minutes in my backyard, still, I'm happy with that. I've got an MPCC in the mail
I can't wait to be able to use the WHOLE sensor, and I do have a Bahtinov mask but I was lazy last night, I just used BEOS and the moon to get the focus close before moving to fainter targets.
I gave it another stack without the 10 minute frames and it seems to have taken the colour cast off the image without taking too much detail away.