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{{Short description|Astronomical catalogue of deep sky objects}}
{{Italic title}}
{{Infobox astronomical survey|name=''New General Catalogue''}}
{{NGC objects}}
The '''''New General Catalogue of Nebulae and Clusters of Stars''''' (abbreviated '''NGC''') is an [[astronomical catalog]]ue of [[deep-sky object]]s compiled by [[John Louis Emil Dreyer]] in 1888. The NGC contains 7,840 objects, including [[galaxy|galaxies]], [[star cluster]]s and [[emission nebula]]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 Herschel|William]] and [[Caroline Herschel]], and [[John Herschel]]'s ''[[General Catalogue of Nebulae and Clusters of Stars]]''. Objects south of the [[Celestial sphere|celestial equator]] are catalogued somewhat less thoroughly, but many were included based on observation by [[John Herschel]] 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.<ref>[http://www.klima-luft.de/steinicke/ngcic/rev2000/NI2019.zip RNGC/IC 2019]</ref>

==Original catalogue==
{{See also|List of NGC objects|Category:NGC objects|List of stars in the 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 Herschel|John]], among others. Dreyer had already published a supplement to Herschel's ''[[General Catalogue of Nebulae and Clusters]]'' (GC),<ref>
{{cite journal
 |last=Dreyer |first=J. L. E.
 |date=1878
 |title=A Supplement to Sir John Herschel's "General Catalogue of Nebulae and Clusters of Stars"
 |url=https://archive.org/details/supplementtosirj00dreyrich
 |journal=[[Transactions of the Royal Irish Academy]]
 |volume=26 |pages=391–426
 |bibcode=1878TRIA...26..381D
 |jstor=30079091
}}</ref> 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.<ref name="HaleBradt">
{{Cite book
 | last=Bradt | first=H.
 | date=2004
 | title=Astronomy Methods: A Physical Approach to Astronomical Observations
 | pages=52
 | publisher=[[Cambridge University Press]]
 | isbn=978-0-521-53551-9
}}</ref><ref name="Dryer1888">
{{cite journal
 |last=Dreyer |first=J. L. E.
 |date=1888
 |title=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
 |url=https://archive.org/download/newgeneralcatalo00dreyrich/newgeneralcatalo00dreyrich.pdf
 |journal=[[Memoirs of the Royal Astronomical Society]]
 |volume=49 |pages=1–237
 |bibcode=1888MmRAS..49....1D
}}</ref>

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.<ref name=history>{{cite web
 |last=Corwin
 |first=H.G. Jr.
 |date=12 October 1999
 |title=The NGC/IC Project: An Historical Perspective
 |url=http://www.ngcicproject.org/history.htm
 |publisher=The NGC/IC Project
 |access-date=2012-04-22
 |archive-url=https://web.archive.org/web/20120510214957/http://www.ngcicproject.org/history.htm
 |archive-date=10 May 2012
 |url-status=dead
 }}</ref>

==''Index Catalogue''==
{{See also|List of IC objects|Category:IC objects}}
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,<ref>
{{cite journal
 |last=Dreyer |first=J. L. E.
 |date=1895
 |title=Index Catalogue of Nebulae found in the years 1888 to 1894, with Notes and Corrections to the New General Catalogue
 |journal=[[Memoirs of the Royal Astronomical Society]]
 |volume=51 |pages=185–228
 |bibcode=1895MmRAS..51..185D
}}</ref> containing 1,520 objects) and 1908 (IC II,<ref>
{{cite journal
 |last=Dreyer |first=J. L. E.
 |date=1910
 |title=Second Index Catalogue of Nebulae and Clusters of Stars; containing objects found in the years 1895 to 1907, with Notes and Corrections to the New General Catalogue and to the Index Catalogue for 1888–94
 |url=https://archive.org/download/secondindexcatal00dreyrich/secondindexcatal00dreyrich.pdf
 |journal=[[Memoirs of the Royal Astronomical Society]]
 |volume=59 |pages=105–198
 |bibcode=1910MmRAS..59..105D
}}</ref> containing 3,866 objects). It serves as a [[supplement (publishing)|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.<ref>
{{cite journal
 |last=Dreyer |first=J. L. E.
 |date=1912
 |title=Corrections to the New General Catalogue resulting from the revision of Sir William Herschel's Three Catalogues of Nebulae
 |journal=[[Monthly Notices of the Royal Astronomical Society]]
 |volume=73 |pages=37–40
 |bibcode=1912MNRAS..73...37D
 |doi=10.1093/mnras/73.1.37
|doi-access=free
 }}</ref>

==''Revised New General Catalogue''==
[[File:NGC 6543 7662 7009 6826.jpg|thumb|upright=1.2|Four different [[planetary nebula]]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.<ref>
{{cite book
 |last1=Sulentic
 |first1=J. W.
 |last2=Tifft
 |first2=W. G.
 |date=1973
 |title=The Revised New Catalogue of Nonstellar Astronomical Objects
 |publisher=[[University of Arizona Press]]
 |isbn=978-0-8165-0421-3
 |bibcode=1973rncn.book.....S
 |url-access=registration
 |url=https://archive.org/details/revisednewgenera0000sule
 }}</ref> 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.<ref name="Steinicke2010">
{{cite web |last=Steinicke |first=W. |date=17 January 2012 |title=Revised New General Catalogue and Index Catalogue |url=http://www.klima-luft.de/steinicke/ngcic/rev2000/Explan.htm |access-date=2012-04-22}}</ref><ref name=history/>

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".<ref>{{cite web|title=Monograph No. 1 - The "Non-Existent" Star Clusters of the RNGC|url=http://www.webbdeepsky.com/nebulae-clusters/mono1|website=Webb Deep-Sky Society|access-date=29 May 2017}}</ref> 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.<ref>{{cite book|last1=Allison|first1=Mark|title=Star Clusters and How to Observe Them|date=4 April 2006|publisher=Springer Science & Business Media|pages=62–63|url=https://books.google.com/books?id=AgkCl1L1G2cC&pg=PA62|access-date=29 May 2017|isbn=9781846281983}}</ref>

As another example, [[reflection nebula]] NGC 2163 in [[Orion (constellation)|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.<ref>{{cite book|last1=O'Meara|first1=Stephen James|title=Deep Sky Companions: Hidden Treasures|date=12 April 2007|publisher=Cambridge University Press|pages=175–176|url=https://books.google.com/books?id=a6VY0Q1zsJoC&pg=PA176|access-date=30 May 2017|isbn=9781139463737}}</ref>

=== ''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.<ref name="Steinicke2010" /><ref>
{{cite book |last=Steinicke |first=W. |title=Observing and Cataloguing Nebulae and Star Clusters: From Herschel to Dreyer's New General Catalogue |date=2010 |publisher=[[Cambridge University Press]] |isbn=978-0-521-19267-5}}</ref> It is a comprehensive and authoritative treatment of the NGC and IC catalogues.<ref>
{{cite journal |last=Duerbeck |first=H. W. |date=2009 |title=Book Review: Nebel und Sternhaufen - Geschichte ihrer Entdeckung Beobachtung und Katalogisierung (Steinicke) |journal=[[Journal of Astronomical History and Heritage]] |volume=12 |issue=3 |page=255 |doi=10.3724/SP.J.1440-2807.2009.03.10 |bibcode=2009JAHH...12..255D|s2cid=258223761 }}</ref><ref>
{{cite journal |last=Duerbeck |first=H. W. |date=2011 |title=Observing and Cataloguing Nebulae and Star Clusters. From Herschel to Dreyer's New General Catalogue (Steinicke) |journal=[[Journal of Astronomical History and Heritage]] |volume=14 |issue=1 |page=78 |bibcode=2011JAHH...14Q..78D}}</ref> 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.<ref name="Steinicke2010"/>

==''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.<ref>{{cite web
 |title=NGC2000 - NGC2000.0: Complete New General Catalog and Index Catalog
 |url=http://heasarc.gsfc.nasa.gov/W3Browse/all/ngc2000.html
 |publisher=[[Goddard Space Flight Center]]
 |access-date=2012-04-22
 |archive-url=https://web.archive.org/web/20121020075827/http://heasarc.gsfc.nasa.gov/W3Browse/all/ngc2000.html
 |archive-date=2012-10-20
 |url-status=dead
 }}</ref><ref>
{{cite book
 |last=Sinnott |first=R. W.
 |date=1988
 |title=NGC 2000.0: The Complete New General Catalogue and Index Catalogues of Nebulae and Star Clusters
 |publisher=[[Sky Publishing]]
 |isbn=978-0-933346-51-2
}}</ref> It incorporates several corrections and errata made by astronomers over the years.<ref name=history/>

==NGC/IC Project==
The NGC/IC Project was a collaboration among professional and amateur astronomers formed 
by [[Steve Gottlieb (amateur astronomer)|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.<ref>{{cite web |title=Steve Gottlieb's NGC Notes |url=https://www.astronomy-mall.com/Adventures.In.Deep.Space/steve.ngc.htm |publisher=astronomy-mall |access-date=9 April 2024 |archive-url=https://web.archive.org/web/20240226201755/https://www.astronomy-mall.com/Adventures.In.Deep.Space/steve.ngc.htm |archive-date=26 February 2024}}</ref> 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.<ref>{{cite web|url=http://ngcicproject.observers.org/|title=The NGC/IC Project|access-date=2020-06-07}}</ref>

==See also==
* [[Messier object]]
* ''[[Catalogue of Nebulae and Clusters of Stars]]''
* [[Astronomical catalog]]
* [[List of astronomical catalogues]]
* [[List of NGC objects]]

==References==
{{Reflist}}

== External links ==
{{Commons category|NGC objects}}
{{Commons category|IC objects}}
* [http://spider.seds.org/ngc/ngc.html The Interactive NGC Catalog Online]
* [http://astronomy-mall.com/Adventures.In.Deep.Space Adventures in Deep Space: Challenging Observing Projects for Amateur Astronomers.]
* [http://cdsarc.u-strasbg.fr/viz-bin/VizieR?-meta.foot&-source=VII/1B Revised New General Catalogue]

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[[Category:Astronomical catalogues]]
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[[Category:IC objects| ]]
[[Category:1888 documents]]
[[Category:1888 in science]]