Civil, nautical and astronomical twilight
Sunset is not darkness. There are three named stages between them, and each has a practical definition rather than a poetic one.
Computed from standard astronomical algorithms · Reviewed Oct 2026 · Method
Civil twilight — Sun 0° to 6° below the horizon. There is enough natural light to read outside and to drive without headlights. This is what people mean by "last light", and it is the number that matters if you are trying to get off a hill.
Nautical twilight — 6° to 12° below. The horizon at sea is still faintly visible while the brighter stars are out, which is the combination that let navigators take sextant sightings. Landscape detail has gone.
Astronomical twilight — 12° to 18° below. The sky looks dark to the eye, but the faintest scattered sunlight is still present and it interferes with deep-sky observation. Once the Sun passes 18°, the sky is as dark as it is going to get.
Why this matters more the further south you go
In the far south around midsummer, the Sun never gets 18° below the horizon at all, so astronomical darkness simply does not occur for weeks — the dash in a month table is not a missing value, it is the honest answer. That is why serious astrophotography in New Zealand is a winter activity, and why the aurora and Milky Way seasons run opposite to the tramping season.
Every place page lists civil twilight in the main table.