Common imaging train

Askar 80PHQ + ASI2600MM Pro + EFW 7×36 + OAG-L

The 80PHQ quintuplet is flat-field by design; its figure is a maximum connection length, not a spacing target. 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. The slow f/7.5 cone is kind to the 36 mm filter bore; the tool shows how much focuser range the train leaves.