Always the optimist, I thought if I kept the shots nice and short I'd have no problem.

Well just have a look at this.
ISO800 30sec ED80 and Canon 300D. Widefield of Neptune, somewhere in there

this is going to take some serious curve, levels and subtractive image masking

(Neptune was only 3 deg from moon) Now I understand why they call these shots "lights" as opposed to "darks"