Thanks Rob.
I try to vary it up when I can plus the MW isn't up yet in theses parts so that helps. I have had 300mm for 2 minutes, I wouldn't like to push it further than that.
Yep I have the polar scope for it and Polaris to help, makes it kind of easy.
Well I won't bother with the filter then if it's not needed, maybe on a non comet target but as you say the more light the merrier.