This off-axis guider offers the best solution for guiding as it eliminates the problem of the differential flexure. This effect can arise when a guiding scope is used: while a camera is capturing an image with the main telescope, the guiding scope can flex to a different amount causing a guiding error. In other words, the guiding telescope does not compensate for the mechanical movement of the main telescope during the exposure and as a result, the image can be blurred. An off-axis guider is installed on the main telescope before the camera so this problem does not occur as the guiding and imaging telescope are actually the same instrument. The ZWO off-axis guider uses a prism that deviates part of the light from the main telescope and redirects it to the guiding camera. However, it will not block any light to the sensor or create any shadow if oriented on the right way. For telescopes with long focal lengths, a guiding camera with a large sensor is recommended such as the ASI174MM Mini. The large 8mm x 8mm prism allows to get a large field of view for the guiding camera. That means a wider field of view and therefore higher chances to have a suitable star for guiding. The off-axis guider reduces the overall weight of the telescope as the guiding telescope is not necessary. Specifications Telescope connection M48 x 0.75, M42 x 0.75 (with adapter) Camera connection M48 x 0.75, M42 x 0.75 Sensor size compatibility APS-C and smaller Compatible guide cameras 1.25" barrel cameras, ZWO non-cooled cameras Guide camera interface 1.25" barrel, M42 x 0.75 Optical thickness 16.5 mm SKU ZWO-OAG Instructions 1. If you use a field flattener or a coma corrector that requires a specific distance to the sensor, calculate the necessary spacing first. 2.Remove the prism and connect the body of the OAG to the telescope. 3. Insert the prism in the OAG 4. Connect the guiding camera 5. Connect the T2 (M42 or M48) adapter to the main camera. 6. Connect the camera to the OAG and lock the 3 thumb screws. Check that the prism is positioned on an angle that would not block the imaging area. 7. Focus with the main camera and then slide the prism along with the guiding camera in order to reach the focus. Included items OAG body (with 1.25″ barrel, 5mm extender with M42 thread) M48 adapter for main imaging camera M48-M42 adapter Hex key
