Twilight is the light received from the sun, when the sun is below the horizon, i.e. before the sunrise and after the sunset. Twilight completely ceases in the evening, when the sun is 18° vertically below the horizon. After that, there is total darkness. In the mornings, twilight commences when the sun is 18° vertically below the horizon and ceases at sunrise. The entire period of twilight has 3 stages, Civil, Nautical and Astronomical. Astronomical commences when the sun is 18° below the horizon. Nautical - 12° below the horizon. Civil - 6° below the … [Read more...]