Common imaging train

Askar SQA55 + ASI533MC Pro + filter drawer

The SQA55 is a 55 mm f/4.8 Petzval with a 44 mm image circle; Askar quotes a connection range with 55 mm recommended, measured behind its M48×0.75 rear adapter. 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 16 mm diagonal sits comfortably inside the 44 mm image circle, so only the spacing needs attention.