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twilight

Definition
 

There are three types of twilight; Astronomical, Nautical and Civil.

From a scientific perspective, twilight is defined according to the position of the Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System’s mass….
 (its centre) relative to the horizon. There are three established and widely accepted subcategories of twilight: civil twilight (brightest), nautical twilight and astronomical twilight (darkes

Definition Position of sun
  degrees below the horizon
Night more than 18°
Astronomical twilight 12° – 18°
Nautical twilight 6° – 12°
Civil twilight less than 6°
Day (sun above the horizon)

For comparison, the angular diameter of the Sun is 0.5°.

 

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