Dictionary term
Phase Angle
Direct answer
Phase Angle is the angle at an illuminated body between directions to its light source and observer.
It sets how much of the lit side faces the observer.
It sets how much of the lit side faces the observer.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.Quick reference
- Use when
- Name the vertex body and distinguish phase angle from illuminated fraction.
- Do not use it for
- Clouds, rings, and surface scattering keep brightness from following area alone.
- Reference category
- Astronomy & Skywatching
- Related terms
- Bond Albedo, Geometric Albedo, Solar Elongation, Greatest Elongation
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The story behind Phase Angle
Geometric astronomy used phase angles to model Moon and planet appearances.
Phase Angle: fact and faith, kept distinct
This is a factual astronomy reference. It can support wonder at the created order without becoming a claim of fate, worship, or private revelation.
Phase Angle in numerology
Phase Angle is not a numerology claim. Any numbers attached to it should retain their ordinary scientific, calendrical, navigational, or historical meaning unless a separate symbolic interpretation is clearly labeled.
Why Phase Angle matters
It governs phase appearance, scattering behavior, and brightness corrections.
Phase Angle at work: an example
A phase angle near zero corresponds to a nearly full observed disk.
Where interpretation stops
Phase Angle is presented as sourced astronomy, calendrical, Earth-science, cultural, or instrument-history reference. Definitions should distinguish measured phenomena from civil convention and historical interpretation, preserve location and time dependencies, and avoid turning factual sky data into a deterministic personal claim.
Sources and editorial method
Research references used for this entry include:
- NASA Science: Solar System Exploration - NASA overview of planets, moons, small bodies, rings, and the structure of the Solar System.
- NASA Science: Moon Phases - NASA explanation and visualization of lunar phases and libration.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Also appears in
- Astronomy & Skywatching
- Aliases
- None listed
- Last updated
- 2026-07-16
Build the illumination triangle
Phase Angle in a book is one thing; Phase Angle in your own birth chart is your life. The Oracle casts your real chart and tells you what it means for your love, your work, and your year ahead, in conversation, free.
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More in Astronomy & Skywatching
- Reference Epoch
- Solar Prominence
- True Anomaly
- Apparent Magnitude
- Brown Dwarf
- Elliptical Orbit
- Hill Sphere
- Mean Motion Resonance
Common questions
What is Phase Angle?
Phase Angle is the angle at an illuminated body between directions to its light source and observer.
How is Phase Angle used in an almanac?
Name the vertex body and distinguish phase angle from illuminated fraction.
What should I avoid when interpreting Phase Angle?
Clouds, rings, and surface scattering keep brightness from following area alone.
