nautical twilight


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nautical twilight

See twilight.

nautical twilight

[′nȯd·ə·kəl ′twī‚līt]
(astronomy)
The interval of incomplete darkness between sunrise or sunset and the time at which the center of the sun's disk is 12° below the celestial horizon.

nautical twilight

nautical twilight
That period before sunrise and after sunset when the upper limb of the sun is below the visible horizon and the center of the sun is not more than 12° below the celestial or sensible horizon. During this interval of incomplete darkness, the degree of illumination is such that general outlines are still discernible, although detailed operations become impossible. All the bright stars are visible at this time. It is the time when the navigational stars are visible and the sea horizon is still sufficiently visible to permit celestial observations with a sextant.
References in periodicals archive ?
The two bodies are, however, moving gradually closer together and by the end of September will be 'only' 32[degrees] apart with Saturn just 5[degrees] above the horizon at the start of nautical twilight.
Greatest western elongation occurs on July 30 with Mercury just over 6[degrees] above the horizon at the start of nautical twilight.
Nautical twilight ends when the Sun is 12[degrees] down; astronomical twilight ends when the Sun is 18[degrees] down.
Topspeed Dave Edwards Nautical Twilight (2.20 Sedgefield) Shaped with promise when runner-up over course and distance on her chase debut 12 days ago and, with improvement anticipated, can gain deserved compensation.
On 2013 March 18 the comet will be 6[degrees] above the horizon at the start of nautical twilight as seen from southern England.
How far from the center of a big city must you go at night to have your sky reach a darkness equivalent to that at the end of nautical twilight, when the Sun is 12[degrees] below the horizon?
Rear Admiral, who returns from a 211-day layoff, doesn't always impress with his head carriage, while Nautical Twilight held every conceivable chance before being worn down and beaten two lengths by Love The Leader over course and distance last month.