Occurs when the sun has dropped 12 degrees below the western horizon, and is the instant of last available daylight for the visual control of limited ground operations. At end of evening nautical twilight there is no further sunlight available. See also horizon. (JP 2-01.3)
END OF EVENING NAUTICAL TWILIGHT
Meaning of END OF EVENING NAUTICAL TWILIGHT in English
DOD English dictionary of military terms. Английский словарь военных терминов DOD. 2012