Guide star

A beacon is a long time to check the direction of the observer selected starry sky shots in astronomy. Normally this the telescope or the Astro Count the daily rotation of the sky is tracked in order to achieve a point-like image of the star. Once one of the axes of the instrument deviates only slightly from the celestial axis ( parallel to the Earth's axis ), the stellar images to distort short line tracks. If a beacon targeted and kept in view, the accuracy of tracking increases significantly. See also: tracking (Astronomy)

Even in space guide stars are used to align probes or to control the gyro platforms. Often the star Canopus is to close to the south celestial pole used because it always has a large angular distance from the sun.