ZWO OAG-L

ZWO OAG-L uses a pick-off prism ahead of the camera so the guide camera sees the same tracking errors as the imaging sensor. That makes it the preferred guiding approach for SCTs, RCs, and long refractors.

Setup takes patience: prism height, guide-camera focus, back focus, and filter-wheel spacing all interact. Once dialed in, it is more dependable than a separate guide scope for demanding rigs.