Common imaging train

Sky-Watcher Esprit 120 + 0.77× reducer + ASI2600MC Pro + filter drawer

Sky-Watcher's 0.77× reducer for the Esprit 120 takes the standard 55 mm behind its M48 thread; the stated image circle is well under a full-frame diagonal. 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. The stated 34 mm image circle covers the 28 mm APS-C diagonal — but not a lot more.