2. Overview

The primary function of the autoguider is to compensate for imperfections in the telescope tracking caused by pointing model inaccuracy and gear errors. This is accomplished by measuring the position of the centroid of a bright guide star in the field of view. The change in position from the original Fiducial point is sent to the TCS, which will correct the position of the telescope accordingly. Secondary functions include providing displays of pointing errors, seeing, magnitude, relative transparency and of course displaying the CCD image. With the advent of the AF2 fibre positioning system, the autoguider can be used to report positions of stars in the field of view of its camera.