Sky science
Celestial Meridian
Direct answer
Celestial Meridian: The Celestial Meridian is the great circle through the celestial poles, zenith, and nadir of an observer.
It divides the local sky into eastern and western halves.
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At a glance
- Found in
- Astronomy & Skywatching
- Related
- Right Ascension Hour, Declination Circle, Local Meridian, Hour Angle
It divides the local sky into eastern and western halves.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.
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The story behind Celestial Meridian
Meridian observations once anchored observatory clocks, catalogues, and longitude work.
A one-minute story
The Wandering Stars
How the moving planets were watched, named and found, and what a transit is.
Why Celestial Meridian matters
Crossing it usually marks an object’s upper or lower culmination.
Celestial Meridian in practice: an example
A star at upper culmination crosses the local meridian at its greatest daily altitude.
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.
- U.S. Naval Observatory: Astronomical Data - Authoritative services for celestial positions, rise and set events, phases, and related calculations.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Last updated
- 2026-09-26
Track a meridian passage
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More in Astronomy & Skywatching
- Escape Velocity
- Inferior Conjunction
- North Celestial Pole
- Planetary Transit
- Resolving Power
- Spiral Galaxy
- White Dwarf
- Astronomical Nutation
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Common questions
What is the Celestial Meridian?
The Celestial Meridian is the great circle through the celestial poles, zenith, and nadir of an observer.
What do people get wrong about the Celestial Meridian?
Not every meridian crossing occurs above the horizon.
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