Dawn. Dawn, from an Old English verb dagian: to become day, is the time that marks the beginning of twilight before sunrise.
It is recognized by the appearance of indirect sunlight being scattered in the atmosphere, when the centre of the Sun's disc reaches 18° below the horizon. This dawn twilight period will last until sunrise, as the diffused light becomes direct sunlight.
Dawn begins with the first sight of lightness in the morning, and continues until the sun breaks the horizon. This morning twilight before sunrise, is divided into three categories depending on the amount of sunlight that is present in the sky, which is determined by the angular distance of the centre of the Sun in the morning.
The categories are named: astronomical, nautical, and civil dawn. Astronomical twilight begins when the sky is no longer completely dark after astronomical dawn.
This occurs when the Sun is 18 degrees below the horizon in the morning. At this point a very small portion of the sun's rays illuminate the sky and the fainter stars begin to disappear. Astronomical dawn is often indistinguishable from night, especially in areas with light pollution. Astronomical dawn marks the beginning of astronomical twilight, which lasts until nautical dawn. Nautical twilight begins when there is enough illumination for sailors to distinguish the horizon at sea but the sky is too dark to perform outdoor act
It is recognized by the appearance of indirect sunlight being scattered in the atmosphere, when the centre of the Sun's disc reaches 18° below the horizon. This dawn twilight period will last until sunrise, as the diffused light becomes direct sunlight.
Dawn begins with the first sight of lightness in the morning, and continues until the sun breaks the horizon. This morning twilight before sunrise, is divided into three categories depending on the amount of sunlight that is present in the sky, which is determined by the angular distance of the centre of the Sun in the morning.
The categories are named: astronomical, nautical, and civil dawn. Astronomical twilight begins when the sky is no longer completely dark after astronomical dawn.
This occurs when the Sun is 18 degrees below the horizon in the morning. At this point a very small portion of the sun's rays illuminate the sky and the fainter stars begin to disappear. Astronomical dawn is often indistinguishable from night, especially in areas with light pollution. Astronomical dawn marks the beginning of astronomical twilight, which lasts until nautical dawn. Nautical twilight begins when there is enough illumination for sailors to distinguish the horizon at sea but the sky is too dark to perform outdoor act
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