The catalogue was compiled in the 1880s by J. L. E. Dreyer using observations mostly from William Herschel, and then subsequently expanded with two Index Catalogues (IC I & IC II), adding nearly 5,000 objects.
Objects in the southern hemisphere sky are somewhat less thoroughly catalogued, but many were observed by John Herschel. The NGC contained many errors which have for the most part been eliminated by The NGC/IC Project www.ngcic.org
The NGC was published in the Memoirs of the Royal Astronomical Society as "A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged." (Dreyer J. L. E., 1888, Mem. R. Astron. Soc., 49, 1-237).