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  2. Twilight - Wikipedia

    en.wikipedia.org/wiki/Twilight

    Twilight occurs according to the solar elevation angle θ s, which is the position of the geometric center of the Sun relative to the horizon. There are three established and widely accepted subcategories of twilight: civil twilight (nearest the horizon), nautical twilight, and astronomical twilight (farthest from the horizon).

  3. Polar night - Wikipedia

    en.wikipedia.org/wiki/Polar_night

    Civil" twilight occurs when the Sun is between 0 and 6 degrees below the horizon. Nearby planets like Venus and bright stars like Sirius are visible during this period. [3] "Nautical" twilight continues until the Sun is 12 degrees below the horizon. [4] During nautical twilight, the horizon is visible enough for navigation. [5] "Astronomical ...

  4. Sky brightness - Wikipedia

    en.wikipedia.org/wiki/Sky_brightness

    Twilight (both dusk and dawn) is divided into three 6° segments that mark the Sun's position below the horizon. At civil twilight, the center of the Sun's disk appears to be between 1/4° and 6° below the horizon. At nautical twilight, the Sun's altitude is between –6° and –12°. At astronomical twilight, the Sun is between –12° and ...

  5. Night sky - Wikipedia

    en.wikipedia.org/wiki/Night_sky

    After sunset the civil twilight sets in, and ends when the Sun drops more than 6° below the horizon. This is followed by the nautical twilight, when the Sun reaches heights of −6° and −12°, after which comes the astronomical twilight defined as the period from −12° to −18°. When the Sun drops more than 18° below the horizon, the ...

  6. Sunset - Wikipedia

    en.wikipedia.org/wiki/Sunset

    The second phase is nautical twilight, between 6 and 12 degrees below the horizon. The third phase is astronomical twilight, which is the period when the Sun is between 12 and 18 degrees below the horizon. [2] Dusk is at the very end of astronomical twilight, and is the darkest moment of twilight just before night. [3]

  7. When and what is the winter solstice? Things to know about ...

    www.aol.com/news/winter-solstice-things-know...

    The days are short and the nights are long. That can only mean one thing: The winter solstice is coming. The first day of winter for the northern hemisphere of Earth will begin on Dec. 21 at ...

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  9. Dawn - Wikipedia

    en.wikipedia.org/wiki/Dawn

    The period of twilight is shortest at the Equator, where the equinox Sun rises due east and sets due west, at a right angle to the horizon. Each stage of twilight (civil, nautical, and astronomical) lasts only 24 minutes. From anywhere on Earth, the twilight period is shortest around the equinoxes and longest on the solstices. [citation needed]