Common imaging train

Celestron EdgeHD 8 + 0.7× reducer + ASI2600MC Pro

Celestron's 0.7× reducer for the EdgeHD 8 wants its spacing measured from the reducer's rear metal surface, to within half a millimetre, and is optimised for APS-C. On an EdgeHD the T-adapter is part of the optical length: Celestron's own figure for it is counted here, and the camera threads onto its T2 end. The T2 bore is the limit — fine for APS-C, not for full frame. Reducer, Celestron T-adapter, camera: the T-adapter eats most of the back focus and thin rings finish it.