Sky science
Horizontal Coordinate System
Direct answer
Horizontal Coordinate System: The Horizontal Coordinate System locates an object by altitude above the local horizon and azimuth around it.
It is an observer-centered altitude and azimuth grid.
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At a glance
- Found in
- Astronomy & Skywatching
- Related
- Equatorial Coordinate System, Ecliptic Coordinate System, Galactic Coordinate System, Astronomy
It is an observer-centered altitude and azimuth grid.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.
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The story behind Horizontal Coordinate System
Horizontal coordinates grew from practical observing, surveying, and navigation.
A one-minute story
The Wandering Stars
How the moving planets were watched, named and found, and what a transit is.
Why Horizontal Coordinate System matters
Horizontal Coordinate System turns catalogue positions into directions a skywatcher can follow.
How to read Horizontal Coordinate System
Attach an exact place and time because both coordinates continually change.
Horizontal Coordinate System in practice: an example
Altitude 45 degrees and azimuth 90 degrees places an object halfway up the eastern sky.
Where readings of Horizontal Coordinate System go wrong
Azimuth conventions differ, so identify where zero degrees begins.
Sources and editorial method
Research references used for this entry include:
- U.S. Naval Observatory: Astronomical Almanac Glossary - Definitions for astronomical coordinates, time, reference systems, and observable phenomena.
- NASA Science: Skywatching FAQ - NASA guidance for observing stars, planets, constellations, and changing sky events.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Last updated
- 2026-09-26
Find an object from your horizon
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Common questions
What is the Horizontal Coordinate System?
The Horizontal Coordinate System locates an object by altitude above the local horizon and azimuth around it.
What do people get wrong about the Horizontal Coordinate System?
Azimuth conventions differ, so identify where zero degrees begins.
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