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Related to Galactic Longitude: galactic system
galactic longitude[gə′lak·tik ′län·jə‚tüd]
a coordinate in the galactic system of coordinates. Until 1958 galactic longitude was measured from the ascending node of the galactic equator (the old system). In the new system longitudes are calculated from the direction to the center of the Milky Way Galaxy. Galactic longitude in the old system was denoted by lI and in the new system, by lII. Now, l without the superscript roman numeral II denotes galactic longitude in the new system.