How long twilight

Forces of Nature. Atmospheric Science. What's the Difference Between Twilight and Dusk? Twilight time: Vehicles move on at A highway during sunset in Berlin, Civil twilight occurs when the sun is between 0 degrees and 6 degrees below the horizon. Nautical twilight occurs when the sun is between 6 degrees and 12 degrees below the horizon. Astronomical twilight occurs when the sun is between 12 degrees and 18 degrees below the horizon.

Night is classified when the sun is 18 degrees or farther below the horizon. Dawn and dusk occur when the sun passes a specific point below the horizon, while twilight refers to the phase between those points. Civil dusk occurs when the sun is exactly 6 degrees below the horizon in the evening.

Nautical dusk occurs when the sun is 12 degrees below the horizon. Astronomical dusk occurs when it is 18 degrees below the horizon. Now That's Interesting. Evening civil twilight begins at sunset, and ends when the geometric center of the sun is 6 degrees below the horizon. Under these conditions absent fog or other restrictions, the brightest stars and planets can be seen, the horizon and terrestrial objects can be discerned, and in many cases, artificial lighting is not needed.

Nautical Twilight: Begins in the morning, or ends in the evening, when the geometric center of the sun is 12 degrees below the horizon. In general, the term nautical twilight refers to sailors being able to take reliable readings via well known stars because the horizon is still visible, even under moonless conditions. Absent fog or other restrictions, outlines of terrestrial objects may still be discernible, but detailed outdoor activities are likely curtailed without artificial illumination.

Astronomical Twilight: Begins in the morning, or ends in the evening, when the geometric center of the sun is 18 degrees below the horizon. In astronomical twilight, sky illumination is so faint that most casual observers would regard the sky as fully dark, especially under urban or suburban light pollution.

Under astronomical twilight, the horizon is not discernible and moderately faint stars or planets can be observed with the naked eye under a non light polluted sky. But to test the limits of naked eye observations, the sun needs to be more than 18 degrees below the horizon.

During summer months at higher latitudes , there may be no distinction between astronomical twilight after sunset and astronomical twilight before sunrise.

This happens when the Sun never goes more than 18 degrees below the horizon during the night. Around the North Pole and the South Pole, each day-night cycle spans an entire year. In the summer, the poles experience Polar Day or Midnight Sun , when the Sun is up in the sky for several months; in the winter, during the Polar Night , the Sun does not rise for several months.

The transitions between Polar Day and Polar Night are marked by lengthy twilight periods. Once the Sun has disappeared behind the horizon in the fall, it slowly sinks lower each day, resulting in about two weeks of civil twilight, followed by nautical and astronomical twilight periods of roughly the same length. The opposite occurs in the spring, as the Polar Night draws to a close and the Sun begins to illuminate the atmosphere several weeks before it actually rises.

Sunrise, sunset, and twilight at the South Pole. Topics: Astronomy , Sun , Atmospheric Phenomena. Sign in. Numbers in bold type mean that the twilight lasts all night. In these cases, the table shows the duration from sunset to solar midnight.