Thanks Mike, Greg and Greg, I appreciate your comments.
Thanks for that useful information Greg B, much appreciated. I used the “in camera noise reduction” as I had the time to do this and didn’t really want to get into the taking dark frames process.
I had the 400mm F5.6L fitted on a side by side plate to take some shots of the waning Moon, but unfortunately underestimated how wide 17mm was on the 40D so a few frames were ruined by the red ring poking into the shot in the top right corner!
I have a lot of respect for the guys who shoot these nightscapes away from home; I was able to use EOS Utility on my PC to nail the focus and had access to mains power for the dew heaters that prevented the 17-40mm from dewing up.
Here is a 400mm F5.6L shot of the Moon from the same session.
Cheers
Dennis