thanks for the feedback everyone - I feel a bit better about it now. I have been stacking several images in DSS, but have been having problems opening the TIFFs in photoshop (I have just started a
new thread about this...)
jjjnettie - would setting the in-camera high iso noise reduction have any impact at 400 ISO? To be honest, I can't see that much difference noise-wise between 400 and 800 - but skyglow would get a bit much with 5 minute subs from where I am. So I think shoot at 800 for 1/2 the time....
Next clear night, I will get as many subs as I can, as well as darks and flats, and try again.
Thanks
Adam