The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an

astronomical catalogue An astronomical catalog or catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery. The oldest and largest are star cat ...

of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

star cluster Star clusters are large groups of stars. Two main types of star clusters can be distinguished: globular clusters are tight groups of ten thousand to millions of old stars which are gravitationally bound, while open clusters are more loosely clus ...

s and emission nebulae. 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

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and

Caroline Herschel Caroline Lucretia Herschel (; 16 March 1750 – 9 January 1848) was a German born British astronomer, whose most significant contributions to astronomy were the discoveries of several comets, including the periodic comet 35P/Herschel–Rigolle ...

, 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, experimental photographer who invented the blueprint and did botanic ...

's '' General Catalogue of Nebulae and Clusters of Stars''. Objects south of the

celestial equator The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. This plane of reference bases the equatorial coordinate system. In other words, the celestial equator is an abstract projec ...

are catalogued somewhat less thoroughly, but many were included based on observation by

James Dunlop James Dunlop FRSE (31 October 1793 – 22 September 1848) was a Scottish astronomer, noted for his work in Australia. He was employed by Sir Thomas Brisbane to work as astronomer's assistant at his private observatory, once located at Parama ...

. The NGC contained multiple errors, but attempts to eliminate them were made by the ''Revised New General Catalogue'' (RNGC) by

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and

William G. Tifft William G. Tifft was an astronomer at the University of Arizona. His main interests were in galaxies, superclusters and redshift quantization. He was influential in the development of the first redshift surveys, and was an early proponent of crew ...

in 1973, ''NGC2000.0'' by

Roger W. Sinnott Roger is a given name, usually masculine, and a surname. The given name is derived from the Old French personal names ' and '. These names are of Germanic origin, derived from the elements ', ''χrōþi'' ("fame", "renown", "honour") and ', ' ...

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 Wolfgang is a German male given name traditionally popular in Germany, Austria and Switzerland. The name is a combination of the Old High German words ''wolf'', meaning "wolf", and ''gang'', meaning "path", "journey", "travel". Besides the regula ...

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 (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Carolin ...

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 (Whatever shines should be observed) , predecessor = , successor = , formation = , founder = , extinction = , merger = , merged = , type = NG ...

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 Supplement or Supplemental may refer to: Health and medicine * Bodybuilding supplement * Dietary supplement * Herbal supplement Media * Supplement (publishing), a publication that has a role secondary to that of another preceding or concurre ...

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 art, art, application, and practice of creating durable 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 i ...

. 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

and

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 Reflection or reflexion may refer to: Science and technology * Reflection (physics), a common wave phenomenon ** Specular reflection, reflection from a smooth surface *** Mirror image, a reflection in a mirror or in water ** Signal reflection, in s ...

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.

''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

, using the J2000.0 coordinates. It incorporates several corrections and errata made by astronomers over the years.

NGC/IC Project

The NGC/IC Project is a collaboration among professional and amateur astronomers formed in 1993. Completed by 2017, it aimed to identify all NGC and IC objects, correct mistakes, collect images and basic astronomical data. Primary team members were Harold G. Corwin Jr., Steve Gottlieb, Malcolm Thomson, Robert E. Erdmann and Jeffrey Corder.

''Revised New General Catalogue and Index Catalogue''

The ''Revised New General Catalogue and Index Catalogue'' (abbreviated as ''RNGC/IC'') is a compilation made by

in 2009. It is a comprehensive and authoritative treatment of the NGC and IC catalogues.

References

External links

The Interactive NGC Catalog Online

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

Revised New General Catalogue
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