An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

One of the three twilight phases which is the period before sunrise and after sunset when the center of the Sun's disk is between 6° and 12° below the horizon. This twilight phase is followed or preceded by → civil twilight. See also → astronomical twilight. In clear weather conditions, the horizon is faintly visible during this phase. Many of the brighter stars can also be seen, making it possible to use the position of the stars in relation to the horizon to navigate at sea. This is why it is called nautical twilight.

→ nautical astronomy; → twilight.