Morning
| Event | Time | Sun's height |
|---|
Evening
| Event | Time | Sun's height |
|---|
The three twilights, in plain words
Sunset isn't the end of daylight. The sky keeps glowing for an hour or two because the sun is lighting the air above you from below the horizon. Astronomers cut that glow into three stages by how far the sun has sunk.
Civil twilight runs from sunset until the sun is 6 degrees below the horizon. You can still read outside, and streetlights usually come on near the end of it. In the morning it's the reverse: civil dawn is when there's enough light to work by.
Nautical twilight takes the sun from 6 to 12 degrees down. The name comes from sailors: this is the window when the horizon is still visible and the brighter stars are out, which is what you need to take a sextant reading.
Astronomical twilight is the last stage, 12 to 18 degrees. The sky looks dark, but a faint glow still washes out the dimmest stars and the Milky Way. When it ends, it's true night, and that's the time astronomers and astrophotographers wait for. "Astronomical twilight tonight" is the question they're asking.
Golden hour and blue hour
Two extra rows in the tables above are for photographers. Golden hour is when the sun is up but low, under about 6 degrees above the horizon, and the light turns warm and soft. Blue hour is roughly the civil twilight window, when the sky itself lights everything an even blue. Both are explained in the golden hour guide.
Why some rows say "none"
Far from the equator in summer, the sun never gets 18 degrees below the horizon, so astronomical twilight never ends and there's no true night. Go far enough north and even nautical or civil twilight can run all night. In those cases the table says so instead of inventing a time. The reverse happens above the Arctic Circle in winter, when the sun doesn't rise at all.
How accurate is this?
The times come from the standard sunrise equation using the sun's position for that date and the city's coordinates. They're usually within a minute or two of published almanac values. Hills or buildings on your real horizon will shift what you actually see, and the numbers are for the city center, so a suburb 30 miles east sees each event a minute or so earlier.
Frequently asked questions
What is astronomical twilight?
The period when the sun is between 12 and 18 degrees below the horizon. Once it ends in the evening, the sky is fully dark for astronomy. In the morning, astronomical dawn is the first faint hint of light.
What's the difference between civil, nautical and astronomical twilight?
How far the sun is below the horizon. Civil is 0 to 6 degrees, with enough light for most outdoor activity. Nautical is 6 to 12, with the horizon still visible at sea. Astronomical is 12 to 18, with the sky nearly dark. Past 18 degrees it's night.
When does it get completely dark?
At the end of astronomical twilight in the evening, when the sun is 18 degrees down. In midsummer at high latitudes that never happens and the sky stays in twilight all night.
Related: sunrise, sunset and moon phase, the moon phases guide for planning a dark-sky night, and the forecast for whether you'll see any of it.