Astronomical Coordinate Systems

System	Reference Plane	Reference Direction	"Latitude" Coordinate	Range	"Longitude" Coordinate	Range
Horizon	Horizon plane	North point	Altitude, h; toward the zenith (+) toward the nadir (-)		Azimuth, A; Measured to the east along the horizon from the north point
Equatorial	Plane of the celestial equator	Vernal equinox	Declination, ; toward the north celestial pole (+) toward the  South celestial pole (-)		Right ascension, or R.A.; Measured to the east along the celestial equator from the vernal equinox
Ecliptic	Plane of the Earthís orbit (ecliptic)	Vernal equinox	Celestial Latitude, ; toward the north ecliptic pole (+) toward the south ecliptic pole (-)		Celestial longitude, ; measured to the east along the ecliptic form the vernal equinox
Galactic	Mean plane of the Milky Way Galaxy	Direction to the Galactic center	Galactic latitude, ; Toward the  north galactic pole (+) Toward the south galactic pole (-)		Galactic longitude, ; measured along the galactic equator to the east from the galactic center