At first I was a bit skeptical on the TeleVue focal reducer and Flattener on My Stellarvue SV80S scope but after a few times out this is a thing of beauty. It works wonderfully on the Stellarvue refractor and cuts almost a full stop on exposure. the threaded t-ring adapter on it is great. The optics on it are superb as well and added no visible color. A great deal IMHO for anyone out to image with their scope and wants a little more speed and wider field of view.