The off-axis guider 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 that the guide scope will move relative to the main scope while guiding, giving you a streaky image.
How it works is simple: the prism inside the off-axis guider deflects some of the light coming into the camera and guides it out to the side. This provides a sample of the same light for the guide as enters the camera's sensor. This light is picked up by the attached camera while driving the mechanism. All we need to do is set the desired object in the camera's viewfinder, check the focus and sharpness of the camera and autoguider, and also check that the autoguider is showing the star we want to follow.
The off-axis guider and the camera only work perfectly in one position, so place it on the camera so that the 8mm prism inside the off-axis guider is facing the bottom of the camera. This way the prism does not obscure the camera sensor and the resulting image will be perfect and vignette-free. The manufacturer recommends the product for binoculars up to f/3.8 aperture.
The off-axis guider has a light path of 11 mm, and a Canon bayonet thread is provided for the camera connection, so no separate adapter ring is needed (the device cannot be used with other cameras). It connects to the telescope with an M48 thread, the same thread found on the popular SkyWatcher and Baader coma correctors. To connect to a T2 thread, an M48/T2 constriction ring is required.
To attach a guide camera, a T2 thread is found on the instrument. Our experience has shown that for a guide camera, an ideal backfocus of about 15 mm is recommended for proper fixation. If this value is higher by about 3-4 mm, the guide camera cannot be slid "forward" enough to get a sharp image. If the backfocus value is shorter, it is recommended to use a T2 extension arm, otherwise the fixation will be too far away (e.g. if the backfocus value of the camera is 12.5 mm, we recommend a T2 extension arm of 3 mm).
