File:Azimuth-Altitude_schematic.svg · Wikimedia Commons · See Wikimedia Commons
horizontal coordinate system
Sign in to saveAlso known as az/el system, Alt/Az system, altazimuth system, Alt-Az System, El-Az System
type of celestial coordinate system that uses the observer's local horizon as the fundamental plane
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Horizontal coordinates use a celestial sphere centered on the observer. Azimuth is measured eastward from the north point (sometimes from the south point) of the horizon; altitude is the angle above the horizon.
The horizontal coordinate system is a celestial coordinate system that uses the observer's local horizon as the fundamental plane to define two angles of a spherical coordinate system: altitude and azimuth. Therefore, the horizontal coordinate system is sometimes called the az/el system, the alt/az system, or the alt-azimuth system, among others. In an altazimuth mount of a telescope, the instrument's two axes follow altitude and azimuth.