well after finally managing to get some longer exposures running the other night with the help of the guide camera i have come across the problem of light pollution creeping into the images if they are are of a low altitude , this is really annoying as there is very little i can do about it , on the refractor i have a broadband light pollution filter which works up to about 3 minutes exposure length but going over this is a big no no.
i have come to the conclusion that in the future i must have to choose targets that are higher up in the sky to try and avoid such issues , also i am thinking of dropping the iso down from 800 to 400
perhaps then i may be able to get away with the 5 minute exposures i would like to obtain.
we shall have to wait and see if this is a good solution to the problem
clear skies
colin
Gino Iori
Thanks you for sharing this problem and information with us 3rdrock. Please let us know if it solves your problem.