Common imaging train

Takahashi FC-76DCU + 76D reducer + ASI533MC Pro + filter drawer

The FC-76DCU with its 76D reducer is a compact f/5.5 setup with a 36 mm image circle and a near-55 metal back distance. 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. A 36 mm image circle and a 16 mm diagonal: nothing to vignette, only the spacing to get right.