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Tuesday, February 20, 2018

Pre Dawn Light

Quora: How long before sunrise does the sky start to lighten?
There are three formal stages of twilight.

Civil twilight = Sun between 0 and 6 degrees below the horizon
Nautical twilight = Sun between 6 and 12 degrees below the horizon
Astronomical twilight = Sun between 12 and 18 degrees below the horizon

When the Sun is below 18 degrees it is true night.

How quickly the Sun gets to any of these elevations depends upon latitude and season.

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