What does altazimuth mean?
An altazimuth is an instrument — most commonly a type of telescope mount — designed to point at and follow objects in the sky by adjusting two independent axes: one measuring altitude, the angle above the horizon, and the other measuring azimuth, the angle around the horizon from north. This simple two-axis design contrasts with the equatorial mounts preferred for long-exposure astrophotography, but altazimuth mounts are prized for their sturdiness, intuitive operation, and low cost, making them popular among amateur astronomers and surveyors alike. The word itself carries a linguistic pedigree: 'alt' derives from the Latin altus, meaning high, while 'azimuth' descends from the Arabic as-samt, the same root that produced zenith. Beyond hardware, the term also names the altazimuth coordinate system, in which sky positions are given as altitude and azimuth pairs. Though technical in register, the word rewards anyone curious about how we locate ourselves under the stars.
nounAn altazimuth is an instrument, typically a telescope mounting, that allows a celestial object to be located and tracked by measuring its altitude (angle above the horizon) and azimuth (angle along the horizon) independently.
- An instrument or telescope mounting that positions objects by their altitude and azimuth coordinates.
- A coordinate system (altazimuth or alt-az) in which object positions are specified by altitude and azimuth rather than equatorial coordinates.
"The observatory's new telescope sits on a sturdy altazimuth mount that tracks stars smoothly across the night sky."
"Amateur astronomers often prefer an altazimuth mount for its simplicity when observing planets and the Moon."
"The surveyor used an altazimuth to record both the elevation and bearing of the distant peak."
Standard pluralization applies; the plural appears mainly in discussions of multiple instruments or mounts.
"The club owns several altazimuths for use on public observing nights."
Its name is a hybrid of Latin and Arabic: 'alt' comes from the Latin altus (high), while 'azimuth' traces back to the Arabic as-samt — the same root that gives us the word zenith.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of altazimuth
The word altazimuth was formed in English, likely in the early nineteenth century, by combining 'alt' (from the Latin altus, meaning high) with 'azimuth', which entered European languages from the Arabic as-samt, meaning direction or path, transmitted through medieval astronomical texts in Spanish and other Romance languages. The Arabic root also yields the related word zenith, which shares the same origin. The compound name directly reflects the instrument's function of measuring both altitude and azimuth.
How altazimuth is actually used
A technical term used mainly in astronomy, surveying, and optics; rarely encountered outside these fields. In modern amateur astronomy it frequently appears in the compound form 'altazimuth mount' or abbreviated as 'alt-az'.
Easily confused with altazimuth
Azimuth is the horizontal angle measured along the horizon, whereas an altazimuth is an instrument combining both azimuth and altitude measurements.
An equatorial mount tracks objects using one axis aligned with Earth's rotation, while an altazimuth uses independent horizontal and vertical axes.