Autoguiding and Acquisition at MDM John Thorstensen, Dartmouth
College Basic Concepts and Terminology The MDM telescopes point
pretty accurately, but not to arcsecond accuracy. They track
pretty well, but exposures longer than a minute or so are likely
to be trailed. It's therefore important to be able to acquire
objects and guide the telescope. This document describes how to
do Because the telescopes are on equatorial mounts, the field
does not rotate on the focal plane as the telescope tracks
across the sky. This is a great simplification. To keep the
telescope from drifting off target as it tracks, the usual
strategy is to use an offset guide star. This is a star in some
part of the focal plane away from the science field of view,
which is reflected by a "pickoff mirror", mounted on a movable
guide probe), through some optics into a guide camera. An
autoguiding program watches the guide star, and if it appears to
drift -- indicating that the telescope is going off-target -- it
sends a correcting signal to