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RA: 11h 50m 54s
Dec: −55° 42′ 0″
Ch: MSA:975, U2:428, SA:25
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 12m
Mag: B=9.07, V=8.3
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James Dunlop discovered this cluster from Paramatta, New South Wales, and included it as No. 349 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "a pretty large, faint nebula, 6' or 7' diameter, easily resolvable with slight compression of the stars to the centre, or rather towards the following side of the centre."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as a "cluster, VI class, pretty rich, irregular figure, round with long appendages, gradually pretty much brighter to the middle, 9', stars 13th magnitude."
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Mel 108: A distinct cluster of faint stars.
Described in Union Obs. Circulars, 45-76, p 50. "Nebulae, clusters, etc. on Sydney Plates" as "(Dunlop 349)? RA 11h 44.5m Dec -54° 58' (1875) Cluster of 100 stars, 12-14mag., within a radius of 5'."
Mel 108: Discussed, Based on F-A plates.
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 7' and the class as 1 2 m. He notes: "RA of NGC corrected by -3.6 minutes, it must be the same cluster as Melotte 108."
(Lick Obs Bul, Vol 14, No. 420) notes: "RA of NGC 3960 corrected by -3.6 minutes, it must be the same cluster as Melotte 108."
"Cat. of Open Cl. south of -45° Decl.", Mem. 17 Mnt Stromlo Obs.
The RNGC (Sulentic and Tifft 1973) notes that this is a 9.0 mag open cluster.
"Open clusters towards the Galactic center: chemistry and dynamics." arXiv:1008.3158v1 (2010 Aug 18)
Distance: 1680 pc. Age: 0.70 Gyr. Orbit: perigalacticon = 6.62+/-0.14 kpc; apogalacticon = 10.96+/-0.03; e = 0.247.
Eggen?: * V > 12.5.
15cm - rich cl of f *s, partially res @ 80x. 140x: 12' diam w/120 *s m13+ plus a
few brtr fld *s sup. mod even concen. core 4' across. cl approx circ but
E side has few members. BS, 23Feb1990, LCO.
Included in the discussion of NGC 3918 in "Neat Southern Planetaries - II", by Andrew James:
"NGC 3960/ Mel 108/ Cr 250 / C1148-554/ Bennett 48 (11506-5541) is an open star cluster directly north by exactly 1.5O of NGC 3918. In size of the 107-odd stars, of which 45-odd in the core are visible in moderate apertures. The core covers about 6.0'min.arc. while the cluster's total diameter is more like 18'min.arc. In physical size the stars in cluster occupy and area of 4.0 parsecs. It is a relatively bright cluster with many blue stars with a Trumpler classification is I 2 m (Highly concentrated, medium rich), as first determined by Ruprecht in 1966. Having a total magnitude of 8.8, it is easily visible in a 10cm. telescope. Distance is estimated at 1700 pc. with an age c.1.07 billion years, similar to the age of the Praesepe (M44) in Cancer. (See Figure 5)"
10x50 binocular mounted. 1997-07-08 Dew, no moon. "nothing visible." [Rui Henriques]
1994-01-19: 11x80's, The Boord, 02:00 SAST Could not locate this cluster. Sky conditions good, almost near zenith.
1994-02-17, Die Boord, 11x80 tripod-mounted, inferior conditions - dew. Picked up this cluster as an extremely faint round glow, 13' across max, with a triangle of stars. Although it is an extremely faint presence, I am confident of the sighting. A challenging object.
1997-03-24, Monday. Jonkershoek. 11x80 tripod. Full Moon. Not found, 9.5m certain.
1998-01-24/25, 6-inch f/8.6 Newtonian, Stellenbosch Rifle Range site. A gentle round 5 arcmin glow of tiny starpoints, the whole surface being on the verge of resolution. No concentration, stars evenly distributed and all the same brightness. Extremely rich, with no dark areas, central star or dominant members.
8-inch f/6 Dobsonian
Conditions: Clear, dark.
Sweeping the sky at 48x shows a star-rich field which includes an obvious 25-arcmin triangle of 8-9th mag stars. Along the eastern leg of the triangle lies NGC 3960, a ghostly, round, glow of very delicate starlight. Not surprisingly, it is a Bennett object. Its gentle glow is visible in the 9x50 finder. This will be another of my targets for Bertha (12-inch Dob) at the end of the month, because I don't see the "long appendages" that John Herschel noted.
Location: Campsite (23 16 South 29 26 East)
Sky conditions: 7 magnitude clear.
Instrument: Meade 8" (Super wide angle 18mm eyepiece)
Pretty large open cluster, gradually brighter to the middle. Looks like stars form little arms in a spiral structure to a loose core. One of this extended structures seems a little brighter. Rich open cluster with small pinpoint bright stars in a busy starfield.
8-inch f/10 SCT (EP: 1.25-inch 26mm SP 77x 41' fov; 1.25-inch 18mm SW 111x 36' fov) and 12-inch f/10 SCT (EP: 2-inch 32mm SW 95x 42' fov; 2-inch 14mm UW 218x 23' fov)
This medium large, irregular faint cluster, becomes gradually brighter and denser towards the middle. The loosely scattered, rich open outliers form arms in a spiral structure, which extend outward from this slightly compressed core. The south extending section appears slightly brighter and longer (218x). Generally, it is a busy star-field with a number of lovely bright stars on the outer edges towards north and south. James Dunlop discovered this cluster from Wales. His notes: It is a pretty large, although faint, nebula, easily resolvable with a slight compression of stars towards the centre.
Sky Conditions:The fainter parts of the Milky Way are barely visible.Haziness only visible on the horizon.Atmosphere stable with little interference.
This open cluster is seen as a misty haze which consists of 13th to 14th magnitude. In this object I have counted 56 stars in a fixed diameter and that this cluster is a well detached object.The stars in NGC 3960 is slightly concentrated towards each other.This open cluster measures 6.2'x 4.7'.
The Messier objects
The Bennett objects
The Caldwell list
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