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Type: bright nebula (HII region)
Mag: B=?, V=?
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Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "A very large and very remarkable nebula, which is brighter to the S.f. part, and dies off to the N.p., having a curved form and forked tail. In the head of it is a double star. The nebula is pretty bright, very large, figure irregular, 8' long, 4' broad. Among a vast number of milky way stars." On a second occassion he called it "very bright, very large, 10' long, of a concave or crescent form, sharply terminated inwards, fading away outwards. In a field of about 80 stars. The place is that of a 13th mag star, about the middle of the crescent, or rather nearer the head." His next description reads: "pretty bright, very gradually brighter in the middle, of a falcated or smilunar shape, extending over three-quarters of the field. The place is that of a double star in its vertex or southern extremity." His final observation was recorded as "Place that of the double star near the cusp of the great falcated nebula, whose extent in PD is = 1.3 radius of field = 9.75' In a rich field. A clustering group follows."
Records it as "remarkable, very bright, very large, falcate, double star involved."
Ced 107 (NGC 3199)
Position (1900): RA 10 13.2, Dec - 57 28
Spectrum of nebula: continuous spectrum (inferred from sp.t. of illuminating star)
Classification: Neb associated with mainly one star (which may be multiple) - Fan-shaped object (eg. IC 59)
Size: (not given)
Notes: "NGC 3199 = GC 2067 = h 3239. Disc. 1835. FA 18. (561)."
Burnham calls it a bright, large irregular nebulosity.
A Preliminary Survey of Nebulosities and Associated B-Stars in Carina.
Gum, C.S. (1955) A survey of southern HII regions. Mem.RAS, 67. [1955MmRAS..67..155G]
A Survey of Southern H II Regions published in the RAS Memoirs, Vol. LXVII, identifies his No. 28 with NGC 3199. Gum's Notes for this object read: "Half a ring of nebulosity with HD 89358 [mag 11.1] at the centre of curvature. Possibly associated with the Carina complex of nebulosities, although the modulus derived from average values would place it at a much greater distance that the Eta Carinae complex." He gives the size of the nebula as 12', and the intensity, or "visibility in the particular section of the Milky Way in which the object occurs" is rated as "moderately bright" on a scale of vf - f - mb - b - vb. In his scheme of classifying the large-scale structural features of nebulae, the nebula is rated a "IV", which corresponds to "fainter objects in which the emission is concentrated in a ring or in a incomplete ring." He notes that it corresponds to No. 107 in Sven Cederblad's 1946 catalogue.
The catalogue of Rodgers, Campbell and Whiteoak list it as No. 48, giving it a size of 15' x 10' and calling it a "bright crescent shape."
(Sulentic and Tifft 1973) notes that this is a diffuse nebula.
"WISE morphological study of Wolf-Rayet nebulae" [2015arXiv150306878T]
WR 18: (RA, Dec J2000.0) [10h 17m 02.28s, −57° 54' 46.9"]
Morphological classification: C = Clumpy/Disrupted WR bubbles. (These nebulae present clumpy H-alpha and IR images and/or incomplete arcs or shells. The W4 images reveal for a significant number of cases that the optical and IR clumps are spatially coincident with bow shock-like features. Archetypes of these WR nebulae are those around WR 8 and WR 18, WR35 and WR40.)
Distance = 2.2 kpc.
RCW 48 Photo index by Jim Lucyk: Sky & Tel. 10/74 p225
(Noosa Heads, Queensland, Australia) observing with an 8-inch f/12 SCT, writes in The Webb Society Nebulae and Clusters Section Report No. 10, July 1992: "Quite large and bright object. Appears like a mottled, inverted comma. Responds well to UHC filter."
Notes that "it is a large diffuse fairly bright broad crescent about 7' x 3', convex S.p. and well defined N.f. by a dark bay, with many stars involved. The field is beautiful, sown with small pairs and triplets in a striking manner. A 6-inch shows the form of the nebula faintly but definitely."
Hartung calls it a "remarkable gaseous nebula; it is a large diffuse fairly bright broad crescent about 7' x 3', convex S.p. and well defined N.f. by a dark bay, with many stars involved. The field is beautiful, sown with small pairs and triplets in a striking manner. A 4-inch shows the form of the nebulosity faintly but definitely."
Sanford calls it a "bright nebula situated in a field of scattered stars. There is dark material surrounding it, forming a 'bay' on the northeast side."
QBS: dk strip on inside of arc prob due to lack br fld *s rather than true obscuration. br * S end ~4' from center.
15cm - lg br emission neb nicely enhanced by UHC & [OIII]. best @ 80x due to size. 12'x8' overall, but in shape of 12'x3' curve opening E, brtr at S end w/sharp edge there running E-W. somewhat broader & more diffusely-edged going N. Wrn boundary diffuse throughout. E edge vsharp, the immed edge perhaps having dk strip along it. at `focus' of curve is little triple of f *s. nr S end at W edge is m11.5 *. fntst part fans off curve to NW, reaching a sm grp of *s there. BS, 21Feb1990, LCO.
Alldays (22.50S, 20.12E, 770m).
12-inch f/10 SCT (95x, 218x)
Consist of a half moon of stars that shows the way to this large faint diffused nebula. Embedded into a multitude of stars, small pairs and even triplets involved. In the dark region east of the nebula there appears to be an island of very faint stars. The double star is yellow in colour.
The Messier objects
The Bennett objects
The Caldwell list
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