I bought this Celestron T-ring to adapt a Televue Pronto to a Canon 40D. It does work but the fit is very loose and sloppy. It does not make me convinced that the camera is securely supported or that it holds the camera with any precision (optically speaking) to the scope.One other problem, at shutter speeds of 1/4000 or faster and using the live-view mode of the 40D, there is an under-exposed strip on the bottom of each exposure. Because I haven't tried the Canon T-ring I can't say whether this flaw is unique to the Celestron but I would recommend spending a few more bucks for the Canon T-ring for the better fit I would assume it has.