galactic coordinate | A system of coordinates based on the mean plane of the Galaxy, which is inclined about 63° to the celestial equator. Galactic latitude (b) is measured from the galactic equator north (+) or south (-); galactic longitude (l) is measured eastward along the galactic plane from the galactic center. In 1958, because of increased precision in determining the location of the galactic center, a new system of galactic coordinates was adopted, with the origin at the galactic center in Sagittarius at α(1950) = 17h42m.4, δ(1950) = - 28°55'. The new system is designated by a superior roman numeral II (i.e., bII, lII) and the old system by a superior roman numeral I: lII ≈ lI + 32°.31. Galactic coordinates are independent of precession. | | | | coordinate | | |