Civil, Nautical & Astronomical Twilight Explained

Sunrise and sunset

Sunrise and sunset are the moments the top edge of the Sun touches the horizon. Our atmosphere bends sunlight slightly, so the Sun is actually just below the geometric horizon when you see it touching. Calculators account for this with a standard correction.

The three stages of twilight

• Civil twilight: the Sun is between 0° and 6° below the horizon. There is enough light to do most things outdoors without artificial light, and the brightest planets and stars start to appear.

• Nautical twilight: the Sun is between 6° and 12° below the horizon. The horizon at sea is still visible, which sailors historically needed to take star sightings, but most stars are now out.

• Astronomical twilight: the Sun is between 12° and 18° below the horizon. To the eye it looks like night, but faint objects like galaxies and nebulae are still washed out. Below 18°, it is fully dark.

Golden hour and blue hour

Golden hour is the period when the Sun is low in the sky, roughly within 6° of the horizon, giving warm, soft light that photographers love. Blue hour falls during civil twilight, when the Sun is about 4° to 6° below the horizon and the sky turns deep blue.

Why twilight length depends on where you are

Near the equator the Sun sets almost straight down, so twilight is short, often around 20 to 25 minutes for civil twilight. At higher latitudes the Sun sets at a shallow angle and twilight can last much longer. In summer far enough north or south, the Sun never gets 6° below the horizon at all, giving the famous “white nights.”