When seeing conditions are poor, several methods can be used to get a more accurate error signal. If the guide star is bouncing around, the mean error of several centroids can be sent to the TCS, or the tracking window can be made larger to make sure that the guide star is always imaged in the tracking window.
Some instruments impose other requirements on the autoguider whilst guiding. For example, the LDSS image array may need the position of the telescope to be tweaked by a small offset to line up the stars with the slits. The tracking window can be moved manually, while the telescope is moving so that the guide loop does not need to be interrupted during this process. Also, a different guide star could be chosen without breaking the guide loop by moving the telescope and shifting the autoguider tracking window to where the new guide star will appear. The AutoFib instrument expects to guide on one star and centroid another in a different fibre window in the background. This will be supported in a later version of the software.