The ZWO large off-axis guider (OAG-L) is a special device that can be used instead of a guide scope. No need for a guide scope, more accurate guiding, and no need to worry about the guide scope shifting relative to the main scope while guiding, resulting in a streaky image. When taking photographs, it is important to achieve a viewing field without vignetting. This is helped by ZWO's large free aperture off-axis guide, which can be used with cameras with sensor sizes larger than APS-C, up to full-frame sensors.
How it works is simple: the 12x12mm prism inside the off-axis guider deflects some of the light coming into the camera and directs it out to the side. This way, the same light that enters the camera's sensor is used as the sample for the guide. For this large off-axis guider, the manufacturer recommends only ZWO's ASI mini series of guiding cameras.
The ZWO large off-axis guider has an M48 focal plane tilting unit built into the telescope side, which can be removed if necessary. On the camera side, the unit is designed primarily for use with the ZWO 2" filter shifter, without the filter shifter an extra adapter (ZWO OAG-L / M54 adapter) is required for fitting.
The width of the off-axis guider is 17.5 mm, the focal plane tilting unit is 5 mm for a total optical path of 22.5 mm.
