Gidsster

Gidsster is a term used in astronomy to describe a star selected to serve as a reference point for telescope guiding systems during observations. The gidsster provides a stable target for a guiding sensor, allowing real-time corrections to the telescope’s pointing to compensate for mechanical drift, wind, and atmospheric effects.

In autoguiding, a guiding camera monitors the gidsster, and when its image drifts, the control system sends small adjustments to the mount to keep the science target centered. The choice of gidsster is important: it should be bright enough for a reliable signal, relatively isolated from other stars, and located in the same field of view near the science target to experience similar atmospheric conditions. Typical magnitude ranges depend on the detector, but candidates are commonly in the brighter part of the field, for optical cameras roughly 8th to 14th magnitude. The star should be non-variable and not a close visual binary.

Gidssters are usually drawn from standard catalogs such as Gaia, Tycho, or USNO, and are identified automatically by telescope control software. In facilities with adaptive optics, artificial guide stars created by lasers can provide high-order references, while a natural gidsster in the field is often used for tip-tilt corrections.

Limitations include atmospheric changes, field rotation on alt-azimuth mounts, and the risk that a poor choice or a variable nearby star can degrade guiding accuracy. Ongoing improvements in detectors and software continue to enhance autoguiding performance across observing conditions.