altazimutale

Altazimutale, in English often called alt-azimuth, refers to a local horizontal coordinate system and to a two‑axis mounting method used in astronomy and related fields. It describes the position and movement of celestial objects relative to the observer’s location and time, contrasting with the equatorial system that uses right ascension and declination.

In the altazimutale system, position is specified by two angles: altitude and azimuth. Altitude is the angular distance above the horizon, ranging from 0° on the horizon to +90° at the zenith. Azimuth is the direction along the horizon, typically measured clockwise from a reference direction such as north, with common conventions giving 0° = north, 90° = east, 180° = south, and 270° = west. Some contexts use different reference points, so conventions may vary. An object’s altitude and azimuth are defined for a given location and time and describe where to look to see it.

An altazimutale mount is a mechanical support with two perpendicular rotation axes: an altitude (or elevation) axis and an azimuth axis. The altitude axis tilts the instrument up and down, while the azimuth axis sweeps it horizontally around a vertical pivot. This design is widely used on portable telescopes, binocular mounts, and many ground-based tracking devices, especially when compact or simple operation is desired. Modern systems often combine an altazimuth mount with computerized tracking to follow objects across the sky.

Limitations include the need to move both axes to track objects, which produces curved sky paths and can complicate long-exposure imaging near the zenith. Nevertheless, the altazimutale approach remains popular for its intuitive pointing and versatility. See also: equatorial coordinate system, telescope mount.