CooC - Coordinate Conversions (version 3.0)
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Equatorial coordinate system
The direction of the rotation axis of the Earth remains almost constant
and so does the equatorial plane perpendicular to this axis. Therefore the
equatorial plane is a suitable reference plane for a coordinate frame that
has to be independent of time and the position of the observer.
The zero point of the first coordinate is called vernal equinox. This
coordinate is the angle from the vernal equinox measured along the
equator counterclockwise. It is called right ascension, or R.A. The
values are between 0 and 24 hours in format (hours minutes seconds),
where 1 hour = 15 degrees.
The angular separation of a celestial object from the equatorial plane is
not affected by rotation of the Earth. This angle is called declination, or
dec. Declination gets values between -90 and +90 degrees in format
(degrees minutes seconds).
For more information on different coordinate systems, please check
the corresponding
encyclopædia article.
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