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This is the direction of a celestial
object, measured clockwise around the observer's horizon
from north. So an object due north has an azimuth of
0°, one due east 90°, south 180° and west
270°. Azimuth and altitude
are usually used together to give the direction of an
object in the topocentric coordinate system.
Sometimes, south is used as the starting
point for azimuth angles instead of north, but on the
Heavens-Above web site, north is always the origin.
We sometimes include the nearest compass
direction as an abbreviation to help clarify the azimuth
angles value in degrees. Up to three letters are used
and they represent azimuth angles in the following order;
N (0°), NNE (22.5°), NE (45°),
ENE (67.5°), E (90°), ESE (112.5°), SE (135°),
SSE (157.5°), S (180°), SSW (202.5°), SW
(225°), WSW (247.5°), W (270°), WNW (292.5°),
NW (315°), NNW (337.5°)
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Strict definition
The azimuth of a
point on the celestial sphere is defined as the angular
distance measured towards the east, from north, along
the astronomical horizon to the intersection of the
great circle passing through the point and the astronomical
zenith with the astronomical horizon.
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