Common imaging train

Sky-Watcher Esprit 100 flattener + ASI2600MC Pro + filter drawer

The Esprit 100 flattener is 55 mm from its mating surface behind an M48 thread; its 40 mm image circle covers APS-C but not full frame. 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 40 mm image circle covers APS-C, so this is a straightforward 55 mm M48 train.