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RA: 08h 10m 42s
Dec: −12° 50′ 0″
Ch: MSA:834, U2:275, SA:12
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 32m
Mag: B=7.05, V=6.5
Synonyms: H VII-011
Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a considerably rich cluster of compressed, scattered stars above 20' diameter."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "a large, extended, rich cluster. Fills field; stars 12th mag approx. A bright star (6th mag) S.f." The second records reads: "a fine rich cluster of stars 11..13th mag, which fills the field."
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "large loose cluster of stars, chiefly 10th mag, closely N.p. 19 [Puppis], a 6th mag yellow (bright orange) star, attended by a fine group. 19 [Puppis] seems larger than 6th mag to my unaided eye."
Photo Index by Jim Lucyk: Burnhams V3 p1515.
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part I. M.N.R.A.S., 35(5), 159.
Journal BAA, 35, p159
Well defined; 30 'diameter, composed of small stars; Raab thinkgs components probably all dwarfs and the cluster not very distant.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 22' and the class as 2 1 m.
The RNGC (Sulentic and Tifft 1973) notes that this is a 8.0 mag open cluster.
Listed by the Herschel Club, described as "bright central star noticed, with blue tint. Large, scattered with stars of similar magnitude. Surrounding 19 Puppis. 8-inch, 48x."
Steve Coe, observing with a 13" f/5.6, notes: "Bright, large, rich, elongated 2X1, 65 stars of mags 10 to 13 counted at 100X. 19 PUP is on the south side of this cluster. It is a wide triple star, easy at 100X and yellow with two white comes."
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "7M; 20' diameter; dim but populous; 50-plus 11M members; 4.5M 19 PUP is bright star off the SE edge, 15' from center."
This very soothing cluster appears in a 10-inch f/5 at 30x as a matte sprinkling of dim stars with a pale yellow beacon star, 19 Puppis, immediately to its southeast. The 18mm eyepiece shows the cluster better as it is framed more pleasantly The cluster members appear to be coarsely grouped into many small cliques of stars. Fine, delicate, well-scattered. It should be difficult in binoculars. The appearance of this cluster in the 10-inch is very similar to the appearance of M48 [NGC 2548] in 11x80 binoculars. Surprisingly, when I subsequently viewed NGC 2539 with the 11x80's, it was easily visible as a faint glimmering patch of starlight - the view through the 10-inch had led me to believe it would be a challenge in hand-held binoculars.
Alldays (22.50S, 20.12E, 770m).
12-inch f/10 SCT (95x)
A lovely swarm of faint stars in a roundish shape with the bright 19 Puppisi, 4.7 magnitude on the south east edge of the cluster. The stars swarm away from the star in almost a line like a teacher with a school class full of children. Darker areas is visible towards the middle section and the NW section spray out more. Middle quite crowded with faint stars.
Observing site: Little Tycho Observatory
[8h 10m 42s, -12° 50' 0"] A loose cluster of around 30 10mv... stars. 19 Pup, a 4mv G star is 10' southeast of the cluster. WikiSky: Confirmed.
The Messier objects
The Bennett objects
The Caldwell list
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