As sheep said, you want descreen on. What it does is reduce the moire or "flower" pattern you see in a lot of raw scans. If you look at the raw scan of Casper I shared earlier in this thread you can see a good example of the pattern I'm talking about.
Speaking of Casper, I finished working on the akrate69's scan earilier today. Please feel free to still scan your copy though ignition, as the raw scan I was working with had some of that moire I mentioned and although I think I managed to eliminate the worst of it, your image may still come out better!
Casper: Spirit Dimensions