Dawn - Wikipedia

Dawn begins with the first sight of lightness in the morning, and continues until the Sun breaks the horizon. The morning twilight is divided in three phases, which are determined by the angular distance of the centre of the Sun (degrees below the horizon) in the morning. These are astronomical, nautical and civil twilight.

Astronomical dawn

edit Main article: Twilight § Astronomical twilight

 

Astronomical dawn begins when the center of the Sun is 18 degrees below the horizon in the morning. Astronomical twilight follows instantly until the center of the Sun is 12 degrees below the horizon.[5] 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.[6]

Nautical dawn

edit Main article: Twilight § Nautical twilight

Nautical twilight begins when there is enough light for sailors to distinguish the horizon at sea, but the sky is still too dark to perform outdoor activities. It begins when the center of the Sun is 12 degrees below the horizon in the morning. Nautical dawn marks the start of nautical twilight, which lasts until civil dawn.[6][5]

Civil dawn

edit Main article: Twilight § Civil twilight

 

Civil dawn begins when there is enough light for most objects to be distinguishable, so that some outdoor activities can commence. It occurs when the center of the Sun is 6 degrees below the horizon in the morning.[5]

When the sky is clear, it is blue colored, and if there are clouds or haze, then bronze, orange and yellow colors are seen. Some bright stars and planets such as Venus and Jupiter are still visible to the naked eye at civil dawn. This moment marks the start of civil twilight, which lasts until sunrise.[6]