Hey Theo,
after calibrating my monitor I decided that the image was so &*^*^*( that I am embarrassed - My dark levels were so far out that I could see no difference in the bottom 3 grey levels, hence the noise was all but invisible to me. Now that I have the grey levels set properly, the noise is humungous...
and I've deleted the image.......
As to clouds, if I take a long enough exposure, I'm sure I can get through them
cheers
Gary