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Sunrise, sunset, or sun position for any location – U.S. only; Sunrise, sunset and day length for any location – Worldwide; Rise/Set/Transit/Twilight Data – U.S. only; Astronomical Information Center; Converting Between Julian Dates and Gregorian Calendar Dates; Approximate Solar Coordinates; Algorithms for Computing Astronomical Phenomena
Twilight Calculator Compute twilight times. Twilight time calculator Archived 2011-10-14 at the Wayback Machine; Formulae to calculate twilight duration (archived) by Herbert Glarner. The colors of twilight and sunset; HM Nautical Almanac Office Websurf Compute twilight times. Geoscience Australia "Sunrise and sunset times" Compute twilight times.
Blue hour at the Old Cathedral of the Holy Name of Jesus, Bragança in Portugal. The blue hour (from French l'heure bleue; [1] [a] pronounced [lœʁ blø]) is the period of twilight (in the morning or evening, around the nautical stage) when the Sun is at a significant depth below the horizon.
Twilight is the period before sunrise and after sunset in which there is natural light but no direct sunlight. [36] The morning twilight begins at dawn and ends at sunrise, while the evening twilight begins at sunset and ends at dusk. Both periods of twilight can be divided into civil twilight, nautical twilight, and astronomical twilight ...
Twilight patterns are produced during the time period between the beginning of astronomical twilight (when the Sun is 18° below the horizon) and sunrise, or sunset and the end of astronomical twilight. The duration of astronomical twilight depends on the length of the path taken by the Sun below the horizon.
For a certain period after sunset and before sunrise, indirect light from the Sun lightens the sky on Earth; this period is often referred to as twilight. Certain groups, such as Earthly astronomers, do not consider daytime to be truly ended until the Sun's disc is actually well below the Earth's horizon, because of this indirect illumination.
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Diagram showing displacement of the Sun's image at sunrise and sunset Comparison of inferior and superior mirages due to differing air refractive indices, n. Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height. [1]