I'm almost in the same boat as the OP, so i'd also like to hear what you guys have to say. I read a review somewhere, "lenstip?" that showed very little coma wide open. well below what my personal threshold would be for coma. the other option is to get an "astrotrac", for a bit more money, then shoot away at nearly any f stop i want, but then it changes things once you start having your camera moving on even longer exposures.. ay well....I do have Astrotrac and I was able to take some nice wide field pictures of the sky. The problem is with Landscape Astrophotography where the camera has to be steady on a tripod. In addition I read many reviews where the buyers had exchanged their copies a lot until the got a good one (the main problem was decentering).