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It it includes all types of deep space objects, including galaxies , star clusters , emission nebulae and absorption nebulae. Dreyer also published two supplements to the NGC in and , known as the Index Catalogues , describing a further 5, astronomical objects.
Objects in the sky of the southern hemisphere are catalogued somewhat less thoroughly, but many were observed by John Herschel or James Dunlop. Sulentic and William G.
Tifft in , and NGC Sinnott in Dreyer had already published a supplement to Herschel's General Catalogue of Nebulae and Clusters GC ,  containing about 1, new objects. In , he suggested building a second supplement to the General Catalogue , but the Royal Astronomical Society asked Dreyer to compile a new version instead.
Assembling the NGC was a challenge, as Dreyer had to deal with many contradicting 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.
It serves as a supplement to the NGC, and contains an additional 5, objects, collectively known as the IC objects. It summarizes the discoveries of galaxies, clusters and nebulae between and , most of them made possible by photography.
A list of corrections to the IC was published in Tifft in the early s, and was published in , as an update to the NGC. Nearly 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 monograph considered the 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". Five others were duplicates of other entries, 99 existed "in some form", and the other required additional research to resolve.
As another example, reflection nebula NGC 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 being classified as non-existent.
NGC Sinnott , using the J From Wikipedia, the free encyclopedia. New General Catalogue Spiral Galaxy NGC displays numerous spiral arms filled with bright stars, blue star clusters, and dark dust lanes.
It spans about 30, light years, lies about 68 million light years from Earth and can be seen with a small telescope in the constellation of Ursa Major. See also: Category:IC objects.
The Interactive NGC Catalog Online
Transactions of the Royal Irish Academy. Bibcode : RIATr..
Cambridge University Press. Herschel, Bart.
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Memoirs of the Royal Astronomical Society. Bibcode : MmRAS.. Retrieved Monthly Notices of the Royal Astronomical Society. University of Arizona Press.
Bibcode : rncn. Webb Deep-Sky Society. Retrieved 29 May Star Clusters and How to Observe Them.
Deep Sky Companions: Hidden Treasures. Retrieved 30 May Goddard Space Flight Center. Sky Publishing. Journal of Astronomical History and Heritage.
Bibcode : JAHH New General Catalogue 1 to Astronomical catalog List of NGC objects. New General Catalogue to Namespaces Article Talk.
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