Hi,
I've decided to make an experiment withe the 18-200mm lens, even tho I suspected it would be severely affected by aberrations. The suspect turned out to be truth.
Here are 65 shots of 90 seconds each, at 200mm, f/5.6, ISO1600. it's a crop.
http://www.flickr.com/photos/siovene/5494407165/sizes/l
It's been calibrated with 80 darks, 40 offsets and 30 flats. Processed in Iris and Photoshop.