Practical Tips from TS: Newtonian Telescopes with f/5 or shorter focal ratios need a coma corrector for best photographical results. The standard adaptations of many telescopes (including the ones mentioned above) have no provision for attaching such a coma corrector and still being able to reach focus with the telescope. This adaptor is the solution for this problem. A normal coma corrector has a T2 male thread on the camera side. From this thread we have an adaptation to the 2" filter thread. With this extra part you can screw the coma corrector into this adaptor. The corrector will disappear entirely in the inside of the focuser drawtube. As a result it will not add extra length to the optical train.