nautical dusk definition
nautical dusk for a place means the time at sunset when the centre of the sun is at a depression angle of 12 degrees below the ideal horizon for the place.
nautical dusk means the time at which the sun is 12 degrees below the horizon in the evening, being the time in the evening that objects are no longer distinguishable, and the horizon is no longer visible to the naked eye.
nautical dusk means the time in the evening when the sun is 12 degrees below the horizon. “Nautical dawn” means the time in the morning when the sun is 12 degrees below the horizon.