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°.