Gavin James
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Astronomy Deep Sky        

A Brief Guide to Catalogues

All deep sky objects have a variety of catalogue numbers assigned to them. Catalogues are extremely useful to identify the myriad of objects in the night sky. They have been compiled over the years by a whole variety of astronomers for any number of purposes. Here we look at each catalogue referenced in the Deep Sky section.

Messier Catalogue - M

We start with perhaps the most famous of all catalogues, the Messier Catalogue. It is a list of 110 deep sky objects that was compiled by the French astronomer Charles Messier (1730-1817) with the help of his assistant Pierre Méchain. The first version of the catalogue was published in 1774 and contained just 45 objects. The final version was published in 1781, containing 103 objects. In the 20th century astronomers have added a further seven objects to the catalogue based on Messier's observation notes. The last such addition was Messier 110 in 1967.

The irony is that Messier was not looking for deep sky objects and he would have made each entry into his list with a sense of frustration. He was a comet hunter, with 13 comets to his name, and kept this list of nebulous regions of the sky so that he could avoid the comet imposters on future nights. Little did he know that he was in fact compiling a list of some of the most spectacular cosmic objects on view from Earth.

Messier objects are catalogued from 1 to 110 and are indicated by either Messier or M and their number, eg M31, the Andromeda Galaxy. The objects range from open clusters such as M45, the Pleiades, and globular clusters like M13, the Great Hercules Cluster, through supernova remnants such as M1, the Crab Nebula, to galaxies like M51, the Whirlpool Galaxy.

New General Catalogue - NGC & Index Catalogues - IC

The New General Catalogue or New General Catalogue of Nebulae and Clusters of Stars, to give it its full title, is a catalogue of 7,840 deep sky objects, compiled by Danish astronomer John Louis Emil Dreyer and published in 1888. It's not really so new anymore then! It is the largest of the catalogues and contains all categories of deep sky objects; clusters, nebulae and galaxies. Dreyer based his catalogue on the findings of the Herschel family, being William Herschel, his son John and his sister Caroline. An example from the catalogue is NGC 7000, the North America Nebula.

The Index Catalogues are two further supplements that Dreyer published in 1895 and 1908 that describe a further 5,386 astronomical objects. An example from these catalogues is IC 1805, the Heart Nebula.

Caldwell Catalogue - C

The Caldwell Catalogue is a catalogue of 109 star clusters, galaxies and nebulae for observation by amateur astronomers. It was compiled by Sir Patrick Moore and published in December 1995. Moore was not happy that the Messier catalogue (compiled by Messier to avoid confusion in his hunt for comets) was often used by amateurs as a list of suitable targets to observe, buthad several key Northern Hemisphere omissions and very few targets from the Southern Hemisphere. So, he set about compiling his own list that was to include objects such as the Double Cluster, C14, and Omega Centauri, C80. He chose to call it the Caldwell Catalogue with designator C, taken from his full name Sir Patrick Alfred Caldwell-Moore, as to use his popular surname, Moore, with designator M, would only cause confusion with the Messier Catalogue itself.

Sharpless Catalog - Sh1 & Sh2

The Sharpless Catalog is a list of 313 HII regions in the Northern Hemisphere, intended to be a comprehensive list for latitudes north of declination -27°. The list was compiled by the American astronomer Stewart Sharpless. The first edition was published in 1953 containing 142 objects (Sh1) and the second edition was published in 1959 with 312 objects (Sh2). An example is Sh2-157, The Lobster Claw Nebula in Cassiopeia.

Barnard Catalogue - B

The astronomer Edward Emerson Barnard compiled a list of dark nebulae known as the Barnard Catalogue of Dark Markings in the Sky, or Barnard Catalogue for short. The 1919 publication listed 182 nebulae, while the final version, published in 1927, lists 369. The Horsehead Nebula is perhaps the most famous of the Barnard Objects, listed as Barnard 33.

Melotte Catalogue - Mel

The English amateur astronomer John Franklin-Adams (1843–1912) created an early photographic atlas of the sky, based on plates taken at Johannesburg, South Africa, and Godalming, England. It was published posthumously in 1913–1914 and contains 206 charts covering the whole sky, each 15° square, and showing stars as faint as 17th magnitude. Philibert Jacques Melotte, an English astronomer of Belgian emigrant parents, scanned the Franklin-Adams chart plates for star clusters and published his catalogue of 245 objects in 1915. The Melotte catalogue contains both open clusters and globular clusters. An example is Melotte 15, the star cluster at the centre of the Heart Nebula.

Uppsala General Catalogue of Galaxies - UGC

The Uppsala General Catalogue of Galaxies is a catalogue of 12,921 galaxies visible from the Northern Hemisphere that was first published in 1973 by Peter Nilson of the Swedish Uppsala Observatory. The catalogue includes essentially all galaxies north of declination -2° 30', to a limiting diameter of 1' (one arcminute) or limiting apparent magnitude of 14.5. The primary source of data is the blue prints of the Palomar Observatory Sky Survey. It also includes galaxies smaller than 1', but brighter than 14.5 magnitude from the Catalogue of Galaxies and of Clusters of Galaxies.

Catalogue of Principal Galaxies - PGC

The Catalogue of Principal Galaxies was published in 1989 and contains data for 73,197 galaxies. In 2003, the PGC was extended to include 983,261 confirmed galaxies brighter than a blue magnitude of 18 and now constitutes the framework of the HyperLEDA database. The PGC is a primary resource for current data on galaxies, including galaxy designations from 50 catalogues.


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