Civil twilight
Astronomy Civil dawn Civil dusk
Civil twilight is the first twilight phase after sunset and the last before sunrise. Its darker boundary occurs when the sun’s centre is 6° below the horizon.
The sun has gone, but the light has not
After sunset, the upper atmosphere remains illuminated and scatters light towards us. Darkness therefore does not arrive instantly. Evening civil twilight ends when the sun’s centre reaches 6° below the horizon. Morning civil twilight starts at that boundary.
What you can still see
With clear skies and an open view, natural light is often sufficient for many outdoor activities. Bright planets and the first stars appear. Under trees, between buildings or beneath thick clouds, it can already be much darker.
Why its duration changes
Date and latitude determine how steeply the sun crosses the horizon. A shallow path makes twilight last longer. “Half an hour after sunset” is therefore not a universal definition.
A calculated boundary, not a light switch
The time on the astronomy page is useful for planning, but cannot guarantee a particular brightness on every path. Street lighting also changes the impression without changing the astronomical boundary. “Civil” describes a convention, not the behaviour of the people outside.