![]() In the northern hemisphere, this roughly correlates with the area between locations just south of the US-Canadian border and Canadian cities like Edmonton, Alberta. The area experiencing all-night astronomical twilight around the summer solstice lies between about 48☃3′ and 54☃3′ North and South. Timing of the twilight phases where you are Twilight Around the PolesĪt high latitudes and around the summer solstice, the Sun does not move lower than 18° below the horizon, so twilight can last from sunset to sunrise. In Oslo (about 60° North) and the northernmost tip of Antarctica (about 60° South), the same process takes roughly 2 hours and 30 minutes.In New York (about 40° North) and Wellington (about 40° South), during the equinoxes, it takes about 1 hour and 30 minutes from the beginning of astronomical twilight until the Sun rises.For example, in Quito, Ecuador, which is very close to the Equator, astronomical twilight begins only about 70 minutes before sunrise during the equinoxes.Īt higher latitudes, in both the Northern and Southern Hemispheres, the Sun's path makes a lower angle with the horizon, so the twilight phases last longer: In locations where the Sun is directly overhead at noon-for example at the equator during the equinoxes-the Sun traverses the horizon at an angle of 90°, making for swift transitions between night and day and relatively short twilight phases. The duration of each twilight phase depends on the latitude and the time of the year. It marks the beginning of night time and the disappearance of the last shimmer of natural daylight.Īstronomical terms & definitions Timing and Length Similarly, astronomical dusk is the instant when the geometric center of the Sun is 18 degrees below the horizon in the evening. However, unlike the term twilight, which describes a time span, the terms dawn and dusk refer to moments during the transitions between day and night.Īstronomical dawn is the moment when the geometric center of the Sun is 18 degrees below the horizon in the morning. The twilight phases in the morning are often called dawn, while the twilight phases in the evening are referred to as dusk. However, astronomers may be unable to observe some of the fainter stars and galaxies as long as the Sun is less than 18 degrees below the horizon-hence the name of this twilight phase.ĭifferent degrees of twilight in the Astronomical Dawn and Astronomical Dusk Most stars and other celestial objects can be seen during this phase. To the naked eye, and especially in areas with light pollution, it may be difficult to distinguish astronomical twilight from night time. During astronomical twilight, the geometric center of the Sun's disk is between 12 and 18 degrees below the horizon. The 3 twilight phases on a world map Astronomical TwilightĮach twilight phase is defined by the solar elevation angle, which is the position of the Sun in relation to the horizon. ![]() Astronomers differentiate between 3 phases: ![]() Twilight is the time between day and night when the Sun is below the horizon but its rays still light up the sky. ![]() ![]() Business Date to Date (exclude holidays)Īstronomical twilight in Nashville, Tennessee. ![]()
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