To convert between the horizontal and equatorial coordinates
for object X,
we use "The" Astronomical Triangle XPZ,
where Z is the zenith, P is the North Celestial Pole, and X is the object.
Sides of the triangle:
PZ is the observer's co-latitude.
ZX is the zenith distance of X.
PX is the North Polar Distance of X.
Angles of the triangle:
The angle at P is H, the local Hour Angle of X.
The angle at Z is 360 minus A, where A is the azimuth of X.
The angle at X is q, the parallactic angle.
Return to index.