The Three Twilights: Civil, Nautical & Astronomical
The definitions and altitude criteria of the civil, nautical, and astronomical twilights that separate dawn from dusk.
What twilight is
Twilight is the time when the sun is below the horizon but the sky is not fully dark thanks to atmospheric scattering. It is divided into three stages by the sun's altitude.
The three twilights
- Civil twilight (−6°): Bright enough for outdoor activities. It serves as the reference point for when streetlights come on.
- Nautical twilight (−12°): Both the horizon and bright stars are visible, which is traditionally when navigators fixed their position by the stars.
- Astronomical twilight (−18°): The darkest stage; only after this is the sky dark enough for observing celestial objects.
Why it matters
Twilight times are useful for photography, astronomical observation, and planning outdoor activities. For example, the best time to photograph the Milky Way is after astronomical twilight ends.
In the twilight table of this calculator you can see all three stages of both dawn and dusk.