James Dunlop's Catalog of Deepsky Objects

In the years 1823-1827, James Dunlop (1795-1848) observed the southern skies from the Brisbane observatory at Paramatta, New South Wales, Australia. He compiled several catalogs, among them the Brisbane Catalog of over 7000 southern stars, and A Catalogue of Nebulae and Clusters of Stars in the Southern Hemisphere observed in New South Wales of 629 entries for deepsky objects [Dunlop (1828)]. However, many of these objects are badly described, so that John Herschel could only verify 211 of them. New research, led by Glen Cozens, brought up a number of further "real" objects, so that actually roughly over 300 (or about 50 %) seem to belong to "real" deepsky objects. The other half is asterisms and multiple stars which Dunlop's comparatively small instruments (a 9-feet FL, 9-inch aperture reflector with speculum metal mirror, perhaps equivalent to about a modern 6-inch reflector) didn't resolve.

The most spectacular original discovery of Dunlop is perhaps that of peculiar radio galaxy NGC 5128 in Centaurus (also called Centaurus A), his Dunlop 482. Also included in his original discoveries are Sculptor Group galaxies NGC 55 (Dun 507), 300 (Dun 530), and 7793 (Dun 608), and a considerable number of further southern galaxies, diffuse nebulae, open clusters, as well as 23 new globular clusters (plus two independent rediscoveries), and 4 planetary nebulae (NGC 2818=Dun 564, NGC 5189=Dun 252, NGC 5882=Dun 447, and NGC 6563=Dun 606). Dunlop has included 7 Messier objects in his list: M6=Dun 612, M54=Dun 624, M55=Dun 620, M62=Dun 627, M69=Dun 613, M70=Dun 614, and M83=Dun 628. These are all but one (M7) south of his declination limit of Dec=-30:00 (1826); perhaps that cluster was too large and scattered for his telescope.

The Dunlop catalog is arranged in the order of increasing declination or south polar distance, from south to north; objects which are nearest to the South Celestial Pole come first. This explains the late numbering of the comparatively northern Messier objects; M83 is (almost) the northernmost Dunlop object.

This endeavor was the second major effort of a deepsky object survey of the southern skies, after Lacaille's list of 42, of 1751-1752.

Here we offer the following options related to Dunlop's catalog online:

Dunlop 100: 100 highlights from the Dunlop catalog. By Glen Cozens. Also available as ascii file. Also published in Sky & Telescope [Cozens (2001)]
Dunlop 244 - 244 Dunlop objects, identified from John Herschel's GC, Auwers' list of Lacaille's objects, and Glen Cozens' "Dunlop 100." (ascii file)
Short biography of James Dunlop

Links

Parramatta Virtual Observatory, by David Povey, Parramatta City Council

References

James Dunlop, 1828. A Catalogue of Nebulae and Clusters of Stars in the Southern Hemisphere observed in New South Wales. Philosophical Transactions of the Royal Society, Vol. 118, pp. 113-151 [ADS: 1828RSPT..118..113D]
Glen Cozens and Graeme L. White, 2001. James Dunlop: Messier of the Southern Sky. Sky & Telescope, Vol. 101, No. 6 (June 2001), pp. 112-116 [ADS: 2001S&T...101f.112C].

Other Deep Sky catalogs suitable for the amateur

History of the Discovery of the Deepsky Objects

Hartmut Frommert
Christine Kronberg
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Last Modification: September 18, 2007