altazimuth
Noun: An altazimuth is a scientific instrument designed for astronomical observation and navigation. Its primary function is to measure two key coordinates of a celestial body (like a star, planet, or the sun) relative to an observer on Earth: 1. Altitude: The angular height of the object above the observer's horizon (from 0° at the horizon to 90° directly overhead). 2. Azimuth: The compass direction of the object, measured clockwise from true north (from 0° to 360°).
This dual measurement system (altitude-azimuth) gives the instrument its name. It is a type of theodolite adapted for astronomy.
The term altazimuth is used specifically in the contexts of astronomy, surveying, and celestial navigation. It refers to the instrument itself or its mounting system. * The altazimuth mount is a common design for amateur telescopes, allowing them to pivot up/down (altitude) and left/right (azimuth). * Navigators historically used an altazimuth to determine their position at sea by measuring the sun's coordinates.
- The old maritime altazimuth in the museum was essential for ocean navigation before modern GPS.
- For beginner astronomers, a telescope on a simple altazimuth mount is easier to point than one on an equatorial mount.
- By carefully adjusting the altazimuth, the surveyor plotted the exact position of the star.
- Altazimuth Mount: A supporting structure for a telescope or antenna that allows rotation on two perpendicular axes: one vertical (for azimuth) and one horizontal (for altitude). This is contrasted with an , which is aligned with Earth's axis of rotation.
- The measurement principle is fundamental. Even without the physical instrument, the concept of determining an object's altazimuth coordinates is central to observational astronomy and satellite tracking.
- Altazimuthal (adjective): Pertaining to or measured by an altazimuth. (e.g., )
- Theodolite: A precision optical instrument for measuring angles between designated visible points, used in surveying and meteorology. An altazimuth is a specialized type of theodolite for celestial targets.
- Equatorial Mount: A telescope mount that has one rotational axis parallel to Earth's axis, making it easier to track celestial objects as they appear to move across the sky.
- Altitude-azimuth instrument
- Position finder (in a navigational context)
- Horizontal Coordinate System: The astronomical coordinate system that uses altitude and azimuth as its two coordinates to define the location of an object in the sky relative to a specific observer at a specific time and location. An altazimuth instrument directly measures in this system.
- Celestial Navigation: The practice of finding one's way using the sun, moon, stars, and planets. The altazimuth was a key tool for this.
- an instrument that measures the altitude and azimuth of celestial bodies; used in navigation