New General Catalogue

The original New General Catalogue was compiled during the 1880s by John Louis Emil Dreyer using observations from William Herschel and his son John, among others. Dreyer had already published a supplement to Herschel's General Catalogue of Nebulae and Clusters (GC), containing about 1,000 new objects. In 1886, he suggested building a second supplement to the General Catalogue, but the Royal Astronomical Society asked Dreyer to compile a new version instead. This led to the publication of the New General Catalogue in the Memoirs of the Royal Astronomical Society in 1888. Assembling the NGC was a challenge, as Dreyer had to deal with many contradictory and unclear reports made with a variety of telescopes with apertures ranging from 2 to 72 inches. While he did check some himself, the sheer number of objects meant Dreyer had to accept them as published by others for the purpose of his compilation. The catalogue contained several errors, mostly relating to position and descriptions, but Dreyer referenced the catalogue, which allowed later astronomers to review the original references and publish corrections to the original NGC. ==Index Catalogue==

The first major update to the NGC is the Index Catalogue of Nebulae and Clusters of Stars (abbreviated as IC), published in two parts by Dreyer in 1895 (IC I, containing 1,520 objects) and 1908 (IC II, containing 3,866 objects). It serves as a supplement to the NGC, and contains an additional 5,386 objects, collectively known as the IC objects. It summarizes the discoveries of galaxies, clusters and nebulae between 1888 and 1907, most of them made possible by photography. A list of corrections to the IC was published in 1912. ==Revised New General Catalogue==

e. Clockwise starting from the top left: NGC 6543, NGC 7662, NGC 6826, and NGC 7009. The Revised New Catalogue of Nonstellar Astronomical Objects (abbreviated as RNGC) was compiled by Sulentic and Tifft in the early 1970s, and was published in 1973, as an update to the NGC. The work did not incorporate several previously published corrections to the NGC data (including corrections published by Dreyer himself), and introduced some new errors. For example, the well-known compact galaxy group Copeland Septet in the Leo constellation appears as non-existent in the RNGC. Five clusters were duplicates of other entries, 99 existed "in some form", and the other 124 required additional research to resolve. As another example, reflection nebula NGC 2163 in Orion was classified "non-existent" due to a transcription error by Dreyer. Dreyer corrected his own mistake in the Index Catalogues, but the RNGC preserved the original error, and additionally reversed the sign of the declination, resulting in NGC 2163 being classified as non-existent. Revised New General Catalogue and Index Catalogue The Revised New General Catalogue and Index Catalogue (abbreviated as RNGC/IC) is a compilation made by Wolfgang Steinicke in 2009. It is a comprehensive and authoritative treatment of the NGC and IC catalogues. The number of objects with status of "not found" in this catalogue is 301 objects (2.3%). The brightest star in this catalogue is NGC 771 with magnitude of 4.0. ==NGC 2000.0==

NGC 2000.0 (also known as the Complete New General Catalog and Index Catalog of Nebulae and Star Clusters) is a 1988 compilation of the NGC and IC made by Roger W. Sinnott, using the J2000.0 coordinates. It incorporates several corrections and errata made by astronomers over the years. ==NGC/IC Project==

The NGC/IC Project was a collaboration among professional and amateur astronomers formed by Steve Gottlieb in 1990, although Steve Gottlieb already started to observe and record NGC objects as early as 1979. Other primary team members were Harold G. Corwin Jr., Malcolm Thomson, Robert E. Erdmann and Jeffrey Corder. The project was completed by 2017. This project identified all NGC and IC objects, corrected mistakes, collected images and basic astronomical data and checked all historical data related to the objects. ==See also==