The main purpose of the OAG is to use the same optical path as the main camera. This avoids the problem of differential deflection that can occur when using a separate optical system for guiding. In the case of the OAG, a part of the image is picked-off from the edge of the imaging circle which does not block the main CCD. This method provides more accurate guiding and sharper images.
- Useing the same optical path as the main camera
- light & stable