That information for the 216XT is in the 216XT manual. (I think you can download the manual from Meade.) Presumably, the 201XT is likewise documented in its manual. If you're stuck, I can Xerox the appropriate page for you. I have a 216XT on loan from Meade right now. (Shields up... we're not supposed to discuss non-film imaging here :) Clear skies and flat fields, Michael