Guiding through the main imaging telescope to eliminate guide-scope flexure
Astrophotography Fit
Best for long focal length or mirror-based systems where a separate guide scope can drift relative to the imaging camera.
Sagitta Off-Axis Guider - With Stepper Motor 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.
Best paired with
SCT, EdgeHD, RC, or long refractor imaging trains
Sensitive guide cameras with enough sensor area for guide-star choice
Threaded camera/filter-wheel stacks with known back focus
Not recommended for
Very short wide-field rigs where a guide scope is simpler
Beginners who need the easiest possible guiding setup
Imaging trains with no back-focus room for an OAG body
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