(New General Catalogue of Nebulae and Clusters of Stars) basic reference list of star clusters, nebulas, and galaxies. It was compiled in 1888 by Danish astronomer Johan Ludvig Emil Dreyer, who based his work on earlier lists made by the Herschel family of British astronomers. Dreyer included some 8,000 celestial objects, a total raised to about 13,000 by his first and second Index Catalogues (IC), published in 1895 and 1908, respectively. With these supplements the NGC covers the entire sky, although many objects visible with modern instruments are not listed.

An object may be known by several designations; e.g., the Crab Nebula is also called NGC 1952 and M 1, the latter being its number in the Messier catalog.

This info appears verbatim in many places, one of them being http://www.seds.org/messier/xtra/ngc/ngc.html