Helikopter Service Flygerforening

From the CAA Norway VFR Guide 2009

VFR Flights between Sunset and Sunrise.
During the period between the end of evening civil twilight and the beginning of morning civil
twilight all lights within controlled airspace shall be conducted in accordance with the instrument
flight rules.
Civil twilight summary for Norwegian airports may be generated at http://litangen.net/civiltwilight/

Definition of civil twilight:

Civil twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities. Complete darkness, however, ends sometime prior to the beginning of morning civil twilight and begins sometime after the end of evening civil twilight.