Civil Twilight -- For technical definition, please follow this link to the U.S. Naval Observatory Astronomical Applications website.
Clarke orbit -- Geostationary orbit.
CMC -- Complex Monitor and Control, a subsystem at DSCCs.
Civil Twilight When the centre of the Sun is less than 6º below the horizon; normal daylight activities are possible.
Collimation The bringing of the optical components of a telescope into correct alignment.
civil twilight (NASA SP-7, 1965) See twilight, note. civil year (NASA SP-7, 1965) = calendar year. CL-600 challenger aircraft (NASA Thesaurus) Canadair turbofan aircraft with supercritical wings. clad (NASA SP-7, 1965) = cladding.
civil twilight See twilight, note. civil year = calendar year. clad = cladding. cladding A coating placed on the surface of a material and usually bonded to the material. Also called clad.
Civil twilight ends when the center of the sun is 6° below the horizon. Although it is still not very dark, it is necessary to use artificial light to carry out most activities.
Analemma, Annular Eclipse, Anticrepuscular Ray, Aphelion, Astronomical Twilight, Astronomical Unit, Atmospheric Phenomena, Babcock's Dynamo Hypothesis, Carrington Rotation Number, Chromosphere, Circumzenithal Arc, Civil Twilight, Conjunction, Corona, ...
A Dictionary of Astronomy entry for civil twilight
A Dictionary of Astronomy entry for astronomical twilight
The Concise Oxford Dictionary of Music entry for Twilight of the Gods
The Oxford Essential Dictionary of the U.S.
Twilight - civil Civil twilight ends or begins when the Sun is 6° below the horizon.
Twilight - nautical Nautical twilight ends or begins when the Sun is 12° below the horizon.
Civil twilight comprises the interval when the zenith distance, referred to the center of the Earth, of the central point of the Sun's disk is between 90°50' and 96°, nautical twilight comprises the interval from 96° to 102°, ...
of altitude above the horizon, and negative numbers indicate below the horizon --- with negative numbers usually being used in terms of how far below the horizon the sun is situated at a given time [for example, the boundary between civil twilight ...
 See also: Twilight, Atmosphere, Period, Time, Light
  
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