From the product description, at the time of purchase, you would think this is compatible with all telescopes but it needs about 10" of back focus to get into focus. Might be compatible with cassegrain's and some refractor's so long as the back focus has 10" of travel. I cannot comment on the performance of the optics as I was unable to focus with my Newtonian. The extra stars are for a) the great customer support received from the seller ( A++) and b) so people can see it.