Telescope tracking controlled by feedback from real-time sensing of star movements within the field of view (FOV). Movement may be sensed by an electro-optical device, such as a CCD chip, or by the human eye comparing star movement to a eyepiece reticle intersection or a reticle grid. Autoguiding refers to automatic feedback to telescope drives provided by electronic devices, while manual guiding is accomplished by human feedback intervention using slow-motion controls on telescope drives.
No telescope mount can track perfectly, yet for CCD imaging it is necessary to very accurately track the object being imaged. This is done by guiding on a star to make small corrections to the mount to accurately follow the star. This makes up for any errors in the telescope's drive system. Guiding can be done manually by watching a star through a crosshair eyepiece, or, more commonly, by using an autoguider to automatically guide. See also, Unguided Exposure, Autoguider, Self-Guiding, and Track & Accumulate.