Sky science
Astronomical Opposition
Direct answer
Astronomical Opposition occurs when a Solar System body appears roughly opposite the Sun in Earth’s sky.
It is a Sun-Earth-object alignment in longitude.
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At a glance
- Found in
- Astronomy & Skywatching
- Related
- Solar Elongation, Greatest Elongation, Inferior Conjunction, Superior Conjunction
It is a Sun-Earth-object alignment in longitude.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.
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The story behind Astronomical Opposition
Opposition timing became a central feature of planetary observing almanacs.
A one-minute story
The Wandering Stars
How the moving planets were watched, named and found, and what a transit is.
Why Astronomical Opposition matters
Outer planets are commonly visible much of the night and often relatively near Earth around opposition.
How to read Astronomical Opposition
full ephemeris geometry rather than longitude alone speaks to precise separation and distance.
Astronomical Opposition in practice: an example
Mars rises near sunset around opposition and culminates near local midnight.
Where readings of Astronomical Opposition go wrong
Opposition is an astronomical configuration, not an astrological aspect or guaranteed closest approach.
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
Observe an outer planet at opposition
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More in Astronomy & Skywatching
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Common questions
What is Astronomical Opposition?
Astronomical Opposition occurs when a Solar System body appears roughly opposite the Sun in Earth’s sky.
What do people get wrong about Astronomical Opposition?
Opposition is an astronomical configuration, not an astrological aspect or guaranteed closest approach.
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