Compare civil, nautical and astronomical twilight before sunrise and after sunset. The calculator lists their boundary times so you can distinguish a light outdoor scene from the beginning or end of astronomical night.
Solar results
Civil twilight: the brightest transition
Morning civil twilight begins at civil dawn and ends at sunrise. Evening civil twilight begins at sunset and ends at civil dusk. The darker boundary occurs when the Sun’s center is 6° below a level horizon.
This stage is often useful for everyday light planning. Under suitable conditions, outdoor objects remain distinguishable, but shade, cloud and terrain can reduce visibility. Civil twilight does not guarantee a particular brightness for every place or task.
Nautical twilight: a darker sky and horizon
Nautical twilight spans the interval between 6° and 12° below the horizon. It follows civil twilight in the evening and precedes it in the morning. Its name comes from navigation using stars with a visible horizon under appropriate conditions.
For a modern observer, the useful point is the transition: the sky is darker than during civil twilight, but the Sun still contributes light. The time listed as nautical dusk is the end of this evening stage, not its beginning.
Astronomical twilight: the approach to night
Astronomical twilight covers the interval from 12° to 18° below the horizon. Evening astronomical dusk ends it; morning astronomical dawn begins it. When the Sun stays below −18° between those events, that interval is astronomical night.
The label describes the Sun’s contribution to sky brightness. It does not account for a bright Moon, nearby cities or illuminated cloud. Those conditions matter when planning observations of faint stars or deep-sky objects.
Read missing boundaries carefully
A local date may have sunrise and sunset without all three twilight stages. During high-latitude summer, the Sun may dip below the horizon but never reach −12° or −18°. Farther poleward it can remain above the horizon throughout the date.
The calculator shows a dash for a boundary that is not crossed on that local date. Check the complete sequence rather than treating a missing astronomical dusk as a missing sunset.
Photography windows use separate conventions
Golden hour and blue hour are photography terms with chosen altitude bands. They are useful for planning, but they are not additional official twilight stages. This site uses −4° to +6° for golden hour and −6° to −4° for blue hour.
For the formal twilight definitions, see the U.S. National Weather Service explanation. The methodology page describes how those boundaries are calculated here.
Frequently asked questions
How many types of twilight are there?
The standard astronomical classification has three: civil, nautical and astronomical. Each has a morning and evening interval, with named dawn or dusk boundaries.
Is twilight the same as blue hour?
No. Twilight is the broader transition around night. The blue-hour band used on this site occupies only part of civil twilight.
Can twilight last all night?
Yes. At some high-latitude summer locations, evening and morning twilight connect because the Sun never reaches the altitude needed for astronomical night. The exact stages present depend on date and latitude.
Which twilight time should I use for stargazing?
Astronomical dusk is the solar reference for the end of evening twilight. Bright objects may be visible earlier, while faint targets benefit from a darker sky. Moonlight, cloud and light pollution remain separate considerations.