ABSTRACT
One way or another, successful imaging requires a telescope to track the star’s apparent motion, to an incredible accuracy, over the duration of each exposure. For focal lengths of about 1,000 mm, critical work may require ±1/7,000° RMS (±0.5 arc seconds). In context, this is equivalent to the thickness of plastic food wrap film at a distance of 5 m. For many, this is achieved by autoguiding in combination with good polar alignment. Others use a precise tracking model and dispense with guiding altogether. For clarity, they now have their separate chapters. Autoguiding and modeling have many interactions, however, since they are applied to the same dynami system.
