Meade's #777 Off-Axis Guider provides a means during long-exposure astrophotography for the photographer to monitor the tracking of the telescope, assuring that the telescope remains precisely positioned upon the object being photographed.
Like a T-Adapter, the #777 Off-Axis Guider couples the camera body to the telescope. But unlike a common t-mount adapter, it also diverts a small amount of the guidestar's incoming light to be diverted at a right angle. This allows the star's position to be examined for tracking errors with an illuminated reticle eyepiece. Position corrections can then be effected using the telescope's hand controller or drive corrector.
