Takahashi description of this item could be misleading. If you look at several FC100 system charts you will see the EX-Q x1.6 can be used with various types and is available with a variety of Tak couplers/adapters. It has to be fitted next to the focuser and you will need an extension before the diagonal. I chose this version because it fits directly into the 2" focuser of a FC100DF. With the 2" (L) Extension tube, supplied as standard with an FC100, it will allow a Takahashi 1.25" diagonal and any eyepiece to come to focus so no extra parts are needed. The result is an exceptionally sharp and totally colour free visual lunar, planetary or small DSO scope that compliments the shorter native focal length scope. You can save on short fl eyepieces and the extender works with binoviewers too. This makes the overall value very good compared to say a quality barlow/powermate not designed flatten the field or reduce CA as well. (No experience of imaging)