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The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an
astronomical catalog An astronomical catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, Galaxy morphological classification, morphology, origin, means of detection, or method of discovery. The olde ...
ue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and
emission nebula An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emission n ...
e. Dreyer published two supplements to the NGC in 1895 and 1908, known as the ''Index Catalogues'' (abbreviated IC), describing a further 5,386 astronomical objects. Thousands of these objects are best known by their NGC or IC numbers, which remain in widespread use. The NGC expanded and consolidated the cataloguing work of
William William is a masculine given name of Germanic languages, Germanic origin. It became popular in England after the Norman Conquest, Norman conquest in 1066,All Things William"Meaning & Origin of the Name"/ref> and remained so throughout the Middle ...
and Caroline Herschel, and
John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor and experimental photographer who invented the blueprint and did botanical work. ...
's '' General Catalogue of Nebulae and Clusters of Stars''. Objects south of the celestial equator are catalogued somewhat less thoroughly, but many were included based on observation by
John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor and experimental photographer who invented the blueprint and did botanical work. ...
or James Dunlop. The NGC contained multiple errors, but attempts to eliminate them were made by the ''Revised New General Catalogue'' (RNGC) by Jack W. Sulentic and William G. Tifft in 1973, ''NGC2000.0'' by Roger W. Sinnott in 1988, and the ''NGC/IC Project'' in 1993. A ''Revised New General Catalogue and Index Catalogue'' (abbreviated as RNGC/IC) was compiled in 2009 by Wolfgang Steinicke and updated in 2019 with 13,957 objects.


Original catalogue

The original ''New General Catalogue'' was compiled during the 1880s by John Louis Emil Dreyer using observations from
William Herschel Frederick William Herschel ( ; ; 15 November 1738 – 25 August 1822) was a German-British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline Herschel. Born in the Electorate of Hanover ...
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 The Royal Astronomical Society (RAS) is a learned society and charitable organisation, charity that encourages and promotes the study of astronomy, planetary science, solar-system science, geophysics and closely related branches of science. Its ...
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 Photography is the visual arts, art, application, and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is empl ...
. A list of corrections to the IC was published in 1912.


''Revised New General Catalogue''

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. Nearly 800 objects are listed as "non-existent" in the RNGC. The designation is applied to objects which are duplicate catalogue entries, those which were not detected in subsequent observations, and a number of objects catalogued as star clusters which in subsequent studies were regarded as coincidental groupings. A 1993 monograph considered the 229 star clusters called non-existent in the RNGC. They had been "misidentified or have not been located since their discovery in the 18th and 19th centuries". It found that one of the 229—NGC 1498—was not actually in the sky. Five others 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 In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to pe ...
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

*
Messier object The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ' (''Catalogue of Nebulae and Star Clusters''). Because Messier was interested only in finding comets, he created a list of th ...
* '' Catalogue of Nebulae and Clusters of Stars'' *
Astronomical catalog An astronomical catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, Galaxy morphological classification, morphology, origin, means of detection, or method of discovery. The olde ...
* List of astronomical catalogues * List of NGC objects


References


External links


The Interactive NGC Catalog Online

Adventures in Deep Space: Challenging Observing Projects for Amateur Astronomers.

Revised New General Catalogue
{{Authority control Astronomical catalogues 1888 documents 1888 in science