Seasons and sky
Blue Hour
Direct answer
Blue Hour is an informal photographic period of cool, diffuse twilight light before sunrise or after sunset.
Blue Hour is the cool-toned twilight interval favored by photographers.
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At a glance
- Found in
- Seasons & Earth Almanac
- Related
- Nautical Twilight, Golden Hour, Astronomical Season, Equinox
Blue Hour is the cool-toned twilight interval favored by photographers.
A Sun-Earth orientation for seasonal, atmospheric, tidal, and terrestrial terms.
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The story behind Blue Hour
Photography and cinematography popularized the term for a twilight quality artists had long observed.
Why Blue Hour matters
Blue Hour’s balanced sky and artificial-light levels can produce saturated blue scenes, but duration changes with latitude and season.
Blue Hour in practice: an example
A high-latitude summer Blue Hour can last far longer than the brief tropical transition.
Where readings of Blue Hour go wrong
Definitions vary by app, often using different negative solar-altitude ranges; state the method when precision matters.
Sources and editorial method
Research references used for this entry include:
- NOAA Global Monitoring Laboratory: Solar Calculator Glossary - NOAA definitions for solar geometry, atmospheric refraction, and civil, nautical, and astronomical twilight.
- National Weather Service: Atmospheric Optics - NWS science reference for halos, pillars, sundogs, green flashes, rays, and related optical displays.
- Source
- The Great Almanac Dictionary
- Category
- Seasons & Earth Almanac
- Last updated
- 2026-09-26
Plan the cool-light interval
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Common questions
What is Blue Hour?
Blue Hour is an informal photographic period of cool, diffuse twilight light before sunrise or after sunset.
What do people get wrong about Blue Hour?
Definitions vary by app, often using different negative solar-altitude ranges; state the method when precision matters.
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