ngc

NGC stands for the New General Catalogue of Nebulae and Clusters of Stars, a major astronomical catalog of deep-sky objects. Compiled by John Louis Emil Dreyer in 1888, the catalog lists about 7,840 objects, including galaxies, nebulae of various types, and star clusters. It has become a standard shorthand for locating and naming distant celestial objects in the era before modern digital surveys.

Many entries were drawn from observations by William Herschel and his son, as well as other 19th-century astronomers. The original catalog was later expanded by Dreyer through the publication of the Index Catalogue (IC) in two parts (1893 and 1908), which added thousands of objects and refined identifications. The NGC and IC remain foundational for historical records, though modern surveys have refined many identifications.

Each object in the NGC is designated by the letters NGC followed by a number. The catalogue includes both extended extragalactic objects and Galactic objects; notable examples include NGC 1952, the Crab Nebula; NGC 224, the Andromeda Galaxy; NGC 5194, the Whirlpool Galaxy; and NGC 4594, the Sombrero Galaxy. Because some entries were based on imperfect coordinates or misidentifications, some objects have been reidentified or split in later catalogs, and others have been assigned alternative NGC or IC numbers.

Today the NGC remains widely used in astronomy as a concise reference, even as modern surveys provide more precise data. It has historical importance and is frequently cross-referenced with the IC catalog and with modern databases. Limitations include misidentifications, duplicates, and gaps due to the observational limitations of the 19th century.

Outside astronomy, NGC can refer to other entities such as the National Geographic Channel, depending on context; in astronomy, it is almost exclusively the New General Catalogue.