Common imaging train

Takahashi FSQ-106EDX4 + 645RD 0.72× + ASI6200MM Pro + EFW 7×2" + OAG-L

With the 645RD 0.72× reducer the FSQ-106EDX4 becomes an f/3.6 astrograph with a 60 mm image circle and a near-55 metal back distance. Full-frame mono: ZWO only recommends 2" wheels for the 43 mm diagonal, the camera wears its M54 tilt plate, and the wheel and OAG-L bolt on with screws rather than threads. Every bore in this train has to clear the diagonal. At f/3.6 the metal back distance is within a shim of the ZWO three-piece train — and f/3.6 cares about that shim.