
Dusk outside a plane on cruise.
'Dusk' or 'civil dusk' is the time at which the
sun is 6
degrees below the
horizon in the evening. At this time objects are distinguishable and some stars and planets are visible to the naked eye.
[1]
'Nautical dusk' is when the sun is 12 degrees below the horizon in the evening. At this time, objects are no longer distinguishable, and the horizon is no longer visible to the naked eye.
'Astronomical dusk' is the time at which the sun is 18 degrees below the horizon in the evening.
At this time the sun no longer illuminates the sky.
Dusk should not be confused with
sunset, which is the moment when the trailing edge of the Sun itself sinks below the horizon.
References
1. Astronomical Terms at National Oceanic and Atmospheric Administration
See also
★
Dawn
★
Twilight
★
Evening