Astronomical Dusk Time

When true night begins — the Sun is 18° below the horizon and the sky is fully dark.

Finding your city…

Astronomical dusk

--:--

Calculating for your time zone…

Location Date

Enter latitude / longitude

Latitude Longitude Time zone

All sun times for this day

What is astronomical dusk?

Astronomical dusk is the moment the Sun's centre sinks 18° below the horizon, ending evening twilight. From then until astronomical dawn the Sun contributes no light to the sky — the darkest conditions for observing faint stars, galaxies and the Milky Way.

Phase	Sun below horizon	What you see
Civil twilight	0° to 6°	Enough light to work outdoors; brightest planets appear
Nautical twilight	6° to 12°	Horizon still visible at sea; bright stars visible
Astronomical twilight	12° to 18°	Sky looks dark to most people; faint glow remains
Night	more than 18°	No sunlight scattered in the sky

Planning a dark-sky night

Start deep-sky imaging after astronomical dusk and stop at astronomical dawn.
Check moonrise and moonset on the moon phase page — the darkest nights are around new moon.
Times are calculated in your browser from the Sun's position (the same method as NOAA-style solar calculators). They assume a flat horizon at sea level, so mountains, buildings and altitude can shift what you actually see by a few minutes.

Frequently asked questions

How long after sunset is it fully dark?

About 70–75 minutes near the equator and 1.5–2 hours at mid-latitudes, more in summer. At high latitudes in summer it may never get fully dark.

What's the difference between nautical and astronomical dusk?

Nautical dusk is when the Sun is 12° down and the horizon disappears at sea; astronomical dusk is at 18°, when the last glow is gone.

Study smarter with Stuon

Take your focus further.

Turn what you learn into lasting knowledge with active recall, spaced repetition, and simple study tracking.

Continue on Stuon