The way I see it, civil twilight
is a signal that registers.
is when the less than one degree due north of fourth magnitude star Upsilon Geminorum.
VISUAL CAPABILITIES, AMBIENT ILLUMINATION, AND CIVIL TWILIGHT
The time, in local laws, most often correlates with civil twilight
or sunrise and sunset.
Naval Observatory, for the GBR area, sunset occurred at 1637, the end of civil twilight
occurred at 1706, and moonset occurred at 2034.
During civil twilight
, you can read a book outside.
If the airport is closing by the Civil twilight
definition of night (as is used in the pilot-controller glossary), there may be half an hour or so where it's night according to TERPS but not night according to the airport.
Using the midpoint of civil twilight
as an operational definition of the boundary between daylight and darkness (Leibowitz & Owens, 1991), we derived the annual twilight cycle by plotting functions parallel to the solar cycles, 15 min earlier than sunrise and 15 min later than sunset.
I was starting to experience a sense of failure as civil twilight
began impinging on the sky.
ends when the center of the Sun is 6 [degrees] below the true horizon.
is from when the Sun sets till it is too dark to do manual work outside without the aid of artificial light.
From Mauna Kea the ages of the Moon at civil twilight
(when the Sun is 6 [degrees] below the horizon) are -20.