I was having the same problem, I had the gain set too high on the imaging software I was using, and was over-exposing the shots. What camera/scope are you using? And what software do u use to take/edit the shot?
I'm far from an expert though, here's my first successful pic with the gain turned down. Also check out the Article on planetary imaging with a dob... Heaps of useful tips.
http://www.iceinspace.com.au/forum/s...ad.php?t=80224