The duration of each twilight phase depends on the latitude and the time of the year. It marks the beginning of nautical twilight.Īstronomical terms & definitions Timing and Length Similarly, civil dusk is the instant when the geometric center of the Sun is 6 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.Ĭivil dawn is the moment when the geometric center of the Sun is 6 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. Only the brightest stars and planets, like Venus and Jupiter, can be seen with the naked eye.ĭifferent degrees of twilight in the Civil Dawn and Civil Dusk Sunrise and sunset are the moments when the Sun's upper edge touches the horizon.Īs the Earth's atmosphere scatters and reflects much of the Sun's rays, coloring the sky bright yellow and orange, artificial lighting is generally not required in clear weather conditions to carry out most outdoor activities. In the morning, this twilight phase ends at sunrise in the evening it begins at sunset. During civil twilight, the geometric center of the Sun's disk is at most 6 degrees below the horizon. The 3 twilight phases on a world map Civil 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. The moments when 99% of people see sunlight During this twilight phase, the Sun is just below the horizon. Business Date to Date (exclude holidays)Ĭivil twilight in Chicago, Illinois.
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