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Type: bright nebula (HII region)
Mag: B=?, V=?
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NGC 3581. See NGC 3576.
Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "fanshaped, adhering to a star. The 3rd of 6." and also as "a star of 12th magnitude with a fan nebula attached."
records it as a "12th magnitude star with fan-shaped nebula attached, third of six." These six are NGC 3576, 3579, 3581, 3582, 3584 and 3586.
Recorded in "Observations of the Southern Nebulae made with the Great Melbourne Telescope".
See the discussion of Lithograph M.4.35 for the details.
Region around Eta Argo. Union Obs. Circ., No 18, 123-125.
Galactic and Extragalactic Studies, III. Photographs of thirty southern nebulae and clusters. Proc. N.A.S., 26, 31-36.
Ced 113c (NGC 3581)
Position (1900): RA 11 7.7, Dec - 60 46
Star: Anon (Mp=12.:, V=12. :)
Spectrum of nebula: (not classified)
Classification: Nebulous cluster (Patches of neb adhering to individual stars of the cluster, eg. Pleiades)
Size: (not given)
Notes: "Ced 113 A nebulous field discovered by John Herschel in 1834 and catalogued as follows. Ced 113 c = NGC 3581 = GC 2337 = h 3326. (561, 682)."
A Preliminary Survey of Nebulosities and Associated B-Stars in Carina. p43.
Burnham calls it a "faint, small, fanshaped nebulosity, many faint nebulous patches in field, including NGC 3582, 3584, 3579 and NGC 3586." Sanford calls it "a prominent member of a small group of nebulae in the same area as NGC 3532..."
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. 38a with this grouping. Gum 38b is NGC 3603, and he writes: "Two objects linked together with nebulosity (overall dimensions 45' x 15'). Each is of complex structure." For his 38a grouping, he gives the size as 20' x 15' and identifies the group with No. 113 in Sven Cederblad's 1946 catalogue.
The combined grouping of Gum 38a + b are also known as RCW 57, which is commented with "Appears obscuration-bounded and contains bright crescent shaped region 50' x 20'."
(Sulentic and Tifft 1973) notes that this is a diffuse nebula.
Alldays (22.50S, 20.12E, 770m).
12-inch f/10 SCT (218x)
Around the northern side of a 9 magnitude star this faint fan shape nebula is visible. A nice little asterism can be seen towards the west very close to the nebula. An obvious large divided fan-shaped nebula, with a dark band running from SE-NW. Two stars appears as two human eyes to the south of the nebula staring down. Resembles a mask which could be used at a masked ball. Try to locate the other dark areas and it is there with care. I need to do a sketch of this one and surrounding nebula's.
The Messier objects
The Bennett objects
The Caldwell list
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