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Type: reflection nebula
Mag: B=?, V=?
Synonyms: H IV-024
Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a brigh tstar with milky chevelure, 5' long, 4' broad." In the Philosophical Transactions, 1791, Herschel wrote: "January the 6th, 1785. A bright star with a considerably milky chevelure; a ittle extended, 4 or 5' in length, and near 4' broad; it loses itself insensibly. Other stars of equal magnitude are perfectly free from this chevelure. The connection between the star and the chevelure cannot be doubted, from the insensible gradation of its luminous appearance, decreasing as it receded from the centre."
Detection of new nebulae by photography. Annals Harv Coll Obs., 18, 113. Bibcode: [1890AnHar..18..113P]
Photographs taken with the Bache telescope, a photographic 8-inch f/5.5 doublet, covering 10 degrees square, were examined by Mrs M Fleming with a magnifying glass.
Table 1: List of nebulae (p115)
No. 22 "The nebulosity, which is mainly on the following side, takes the form of several spiral rays."
! B, 8'x8', iregular nebula, very bright central star surrounded by bright diffuse nebulsty, the centre of which is almost a rhombus in shape, and outer portions resembling cirrus cloud, in which are dark patches of absorbing matter.
Duncan, J. C. (1921) Bright and dark nebulae near zeta Orionis photographed with the 100-inch Hooker telescope. Astrophys. J., 53, 392-396.
Ced 55o (NGC 2023)
Position (1900): RA 5 36.6, Dec - 2 17
Star: 2 1345 (Mp=7.9, V=7.8, SpT=B2)
Spectrum of nebula: continuous and emission spectrum (observed)
Classification: Neb associated with mainly one star (which may be multiple) - star surrounded by a neb envelope with conspicuous structure (eg. IC 5146)
Notes: "Ced 55 o = NGC 2023 = GC 1226 = H IV 24. Disc. 1785. WP 67. WP 166. FA 98. (114, 174, 196, 216, 235, 294, 296, 366, 416, 578, 630 Pl 34, 631, 715, 724, 817) . R. -2 1345 = HD 37903. Ced 55: The Orion region. History and bibliography: (118, 119, 186, 188, 191, 276, 352). The nebulous groundwork and the exterior nebulosities: (20, 21, 26, 53, 58, 78, 142, 143, 186, 191, 206, 207, 278, 279, 281, 282, 289, 305, 312, 438, 480, 519, 540. 541, 593, 594, 595, 620, 625, 628, 630 Pl 34, 663, 675, 715, 726 No 41, 769, 782, 802, 818). R. It is shown on several photographs, e.g. (630) Pl 34, that the whole region of the constellation Orion is filled up by vast masses of nebulosity. As is well known, there are several condensation which seem to stand out from the general background, and which have been separately discovered and studied. Such subnebulae, will be individually discussed below. Taken as a whole, No 55 of the catalogue should be classified as C. 2 in addition to the separate classes of the subnebulae."
Lynds, B.T. (1962) Catalogue of dark nebulae. Astrophys.J.Suppl.Ser. 7, 1-52. [also: computer datafile: VII/7A]
The RNGC (Sulentic and Tifft 1973) notes that this is a diffuse nebula.
Bernes, C. (1977) A catalogue of bright nebulosities in opaque dust clouds.
NGC 2023 = Bernes 111
= [RK68] 38, VdB 52, Bernes 111, N2023, GN 05.39.1.02, Ced 55o
Class: C (reflection neb)
by Jim Lucyk: Sky&Tel. 9/85 p210, Astronomy mag. 2/84 p84, Sky&Tel. 9/87 p254, 255, 256.
See also "Visual Astronomy of the Deep Sky" by Roger N. Clark (1990, Sky Publishing Corporation) page 106.
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "10' diameter; large, faint nebula; 14' NNE of the "Horsehead" (B-33)."
Steve Coe, using a 13" f/5.6, notes: " Pretty bright, pretty large, irregularly round, this nebula is easily noticed at 100X without the UHC. There is a 9th mag star very near the center and an 11th mag star on the SE edge."
Alldays (22.50S, 20.12E, 770m).
12-inch f/10 SCT (95x, 218x)
This nebula surrounds a 9th magnitude star and if I saw this nebula I realize than I am just a stop away from the famous Horse Head nebula. It is a round to oval haze that grows with averted vision.
8-inch Dobsonian f/5 (EP: 25mm 48x)
Conditions: Clear, dark.
NGC 2023 is a pretty small, distinct glow with its somewhat off centre 9th magnitude star.
The Messier objects
The Bennett objects
The Caldwell list
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