Twilight is the period between daylight and full darkness, defined by how far the sun sits below the horizon. Astronomers divide this into three distinct types of twilight — civil, nautical and astronomical — each based on a precise solar depression angle: 0–6°, 6–12°, and 12–18° respectively. Understanding these phases helps photographers, sailors, astronomers and anyone who wants to know when it gets dark after the sun has set.

What Are the Three Types of Twilight?

The three types of twilight are defined by the Sun’s centre being below the horizon by a specific number of degrees. Once the Sun drops more than 18° below, twilight ends and true night begins. Each stage has practical consequences for visibility and what you can see in the sky.

Here’s a quick breakdown:

  • Civil twilight: Sun 0° to 6° below horizon. Most outdoor activities still possible without artificial light.
  • Nautical twilight: Sun 6° to 12° below horizon. Horizon becomes indistinct; sailors need stars to navigate.
  • Astronomical twilight: Sun 12° to 18° below horizon. Sky is dark enough for most astronomical observations, but faint objects may still be affected by residual light.

The point where twilight ends is the moment when the Sun reaches 18° below the horizon. At that stage, the sky is fully dark.

Civil Twilight — The Brightest Stage

Civil twilight starts the instant the Sun’s upper edge disappears at sunset. During this phase, the horizon remains clearly visible, and there is enough natural light for most outdoor tasks — reading a map, walking without a torch, or even playing outdoor sports. The brightest stars and planets (like Venus or Jupiter) may become visible near the end of civil twilight.

This is also the period photographers call the “golden hour” for its warm, low-angle light, though the golden hour technically overlaps with the final minutes of sunset and the first part of civil twilight. For accurate timings of civil twilight in your location, check Sunrise.am’s sunset times worldwide — the page includes precise start and end times for all three phases.

Nautical Twilight — When the Horizon Fades

As the Sun sinks to 6° below the horizon, nautical twilight begins. The name comes from its importance to sailors: at this stage, the horizon line becomes faint or invisible, making it impossible to distinguish sea from sky using unaided vision. Navigators once relied on stars during nautical twilight to take sextant readings while still having a usable horizon.

On land, general visibility drops. You will need artificial light for detailed tasks. However, the sky still has enough scattered sunlight to silhouette objects clearly. Many landscape photographers find the deep blues and purples of nautical twilight ideal for moody night shots. If you are planning a photo session, knowing the exact start of nautical twilight is as important as knowing Tokyo sun times or any other city’s schedule — the timing shifts with latitude and season.

Astronomical Twilight — The Darkest Phase Before Night

Astronomical twilight begins at 12° solar depression and ends at 18°. To most casual observers, the sky looks fully dark throughout this period — but faint celestial objects are still compromised. Faint galaxies, nebulas and star clusters become clearly visible only after the Sun drops past 18°.

Amateur astronomers know this well: if you try to observe the Milky Way during astronomical twilight, the dimmest stars will be washed out by residual sky glow. Professional observatories generally do not start their main observing runs until astronomical twilight ends. For casual stargazing, though, astronomical twilight still offers a fine view of bright stars and planets.

Remember that at very high latitudes (above 48° or so), summer twilight can last all night if the Sun never dips more than 18° below the horizon — a phenomenon known as “nautical twilight all night” or the “white nights” of cities like Saint Petersburg.

Why the Length of Twilight Varies

Not all twilights are equal. The duration of each type of twilight depends on three factors:

  • Latitude: Closer to the equator, twilight is short — the Sun drops at a steep angle. At high latitudes, the Sun sets at a shallow angle, stretching twilight out.
  • Season: Around the solstices (June and December), twilight durations change because of the Sun’s apparent north–south motion. At the equinoxes (March and September), twilight tends to be shortest at any given latitude.
  • Local topography: Mountains or tall buildings can block the Sun’s direct light, effectively starting twilight earlier than the astronomical calculation suggests.

A practical example: In equatorial Singapore, civil twilight lasts about 20 minutes. In London (51°N), it lasts around 35 minutes in summer but only 30 minutes in winter. If you’re interested in the precise timings for a specific city, the Tokyo sun times page shows how twilight length changes across the year for a mid-latitude location.

Practical Uses for Each Twilight Phase

Knowing which stage of twilight you are in helps you plan activities precisely:

  • Civil twilight: Best for early morning runs, evening walks, outdoor photography without flash.
  • Nautical twilight: Ideal for sailors checking celestial navigation; also great for capturing the blue hour — that deep, cool light just before true night.
  • Astronomical twilight: Perfect for astrophotography of bright deep-sky objects, or for observing meteor showers when the Moon is not present.

For photographers, the transition between civil and nautical twilight is often the most photogenic. The blue hour occurs predominantly during nautical twilight, when the sky takes on an even, rich blue tone. You can read more about this phenomenon in our dedicated post on the blue hour.

Wrap-Up

Twilight is not a single event but a gradual transition through three well-defined stages: civil, nautical and astronomical. Each type of twilight serves a different purpose — from safe outdoor movement to celestial navigation to deep-sky observation. Bookmark Sunrise.am to get the exact start and end times for all three phases at your location, or for any city worldwide, every day of the year. For a deeper understanding of the timing, our article on when it gets dark explains how sunset transitions into full night across different seasons.

Related reading on Sunrise.am: sunset times worldwide, Tokyo sun times, when it gets dark, blue hour.