Common imaging train

ASI2600MM Pro + EFW 7×36 + OAG-L

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. The mono train ZWO designed the pieces around: the camera keeps its tilt plate, the 7×36 wheel bolts to it, and the OAG-L bolts to the wheel with its M48 plate facing the telescope. The unmounted 36 mm filter glass still shifts focus slightly, and the 36 mm bore is the thing to watch on anything larger than APS-C. With a 55 mm optic nothing else should be needed — swap the optic below to check your own flattener.