A coordinate system based on the local
horizon.
The coordinates lines of this system are the:
Azimuth (Az) - measured along the horizon from the North eastwerd.
(e.g. 90^{o} - is East, 180^{o} is South etc.)
Altitude (Alt) (or Elevation, or zenith distance=90^{o}-Altitude) -
This is the angle between the object and the
horizon
measured on the
great circle
defined by the zenith and the object.
The Transformation between the horizonatl coordinates system and the
equatorial coordinates system is given by:
cos(Alt) sin(Az)
= -cos sin h
cos(Alt) cos(Az)
= sin cos - cos cos h sin
sin(Alt)
= sin sin + cos cos h cos
Where is the
Declination, h is the
Hour Angle and
is the
geocentric latitude.
(These formule, don't take into account the
refraction in the
Earth atmosphere.
Convert Equatorial Coordinates to
Azimuth and Altitude