Common imaging train

ZWO FF80 + 0.76× reducer + ASI2600MC Pro + filter drawer

ZWO's 0.76× reducer for the FF80 brings it to f/5.7 and asks for the standard 55 mm behind its M48×0.75 filter thread. One-shot colour usually runs a single dual-band filter in a drop-in drawer instead of a wheel. The M42 drawer threads straight onto the camera and leaves a gap that one of the extenders in the camera box closes — once the filter glass is accounted for. An all-ZWO train where the boxed extender is meant to be the answer — the filter glass is why it is not exact.