Dictionary term
Astronomical Dawn
Direct answer
Astronomical Dawn is the morning instant when the Sun center rises through 18 degrees below the horizon.
Astronomical Dawn begins astronomical twilight at a -18-degree solar altitude.
Astronomical Dawn begins astronomical twilight at a -18-degree solar altitude.
A Sun–Earth orientation for seasonal, atmospheric, tidal, and terrestrial terms.Quick reference
- Use when
- Use Astronomical Dawn to close an overnight observing window and plan long-exposure astronomy.
- Do not use it for
- Light pollution, airglow, Moon, and high-latitude summer can make practical darkness differ from the calculated boundary.
- Reference category
- Seasons & Earth Almanac
- Related terms
- Nautical Dusk, Astronomical Dusk, Astronomical Season, Equinox
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The story behind Astronomical Dawn
The eighteen-degree standard provided observatories a repeatable boundary for residual solar illumination.
Astronomical Dawn in spiritual tradition
Spiritually, Astronomical Dawn can mark the quiet first return of solar influence without turning darkness into fear.
Astronomical Dawn: fact and faith, kept distinct
This is a factual calendar, astronomy, Earth-science, cultural-history, or observational reference. It can support wonder and practical planning without becoming a claim of fate, spiritual causation, or private revelation.
Astronomical Dawn in numerology
Astronomical Dawn 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 Astronomical Dawn matters
It marks the conventional end of full natural night for sensitive sky observation.
Astronomical Dawn at work: an example
Faint-object imaging often ends near Astronomical Dawn, before any visible sunrise glow for casual observers.
Where interpretation stops
Astronomical Dawn 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:
- U.S. Naval Observatory: Rise, Set, and Twilight Definitions - Official definitions used for sunrise, sunset, refraction, and twilight calculations.
- NOAA Global Monitoring Laboratory: Solar Calculator Glossary - NOAA definitions for solar geometry, atmospheric refraction, and civil, nautical, and astronomical twilight.
- Source
- The Great Almanac Dictionary
- Category
- Seasons & Earth Almanac
- Also appears in
- Seasons & Earth Almanac
- Aliases
- None listed
- Last updated
- 2026-07-16
Close the dark-sky session safely
Astronomical Dawn in a book is one thing; Astronomical Dawn 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 Seasons & Earth Almanac
Common questions
What is Astronomical Dawn?
Astronomical Dawn is the morning instant when the Sun center rises through 18 degrees below the horizon.
How is Astronomical Dawn used in an almanac?
Use Astronomical Dawn to close an overnight observing window and plan long-exposure astronomy.
What should I avoid when interpreting Astronomical Dawn?
Light pollution, airglow, Moon, and high-latitude summer can make practical darkness differ from the calculated boundary.
