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NGC 6520 (14,886 of 18,816)

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NGC 6520

NGC 6520, Cl Collinder 361, C 1800-279, Cl VDBH 255, COCD 426, VII 7, h 3721, GC 4358

RA: 18h 03m 24s
Dec: −27° 53′ 0″

Con: Sagittarius
Ch: MSA:1415, U2:339, SA:22

Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)

(reference key)

Type: open cluster, 12rn

Mag: B=?, V=7.6

Size: 2′
PA: ?

Historical observations

William Herschel (c.1784)

Synonyms: H VII-007

Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a considerably rich but pretty compressed, scattered cluster of stars, a little more compressed in the middle."

John Herschel (1847) Cape Observations

Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "a pretty compact cluster class VII of stars 9..13m; irregularly scattered, diam 4'."

Published comments

Trumpler, R.J. (1928)

Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 4.5' and the class as 2 3 m.

Raab, S. (1922)

Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.

Discussed, based of F-A plates.

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 7.5 mag open cluster.

Photo index

Photo Index by Jim Lucyk: Sky&Tel. 8/86 p130, Astronomy mag. 11/84 p11, Deep Sky #3 Su83 p8, Astronomy mag. 9/87 p50.

Melotte, P.J. (1915)

A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.

Modern observations

Harrington, Phil

Harrington writes: "With persistence, NGC 6520 can be seen as a faint smudge through 7x binoculars. Although a 4-inch telescope at low magnification shows a little more, higher powers and larger apertures are needed to unveil the cluster's true nature - a rich school of faint stars swarming in the stream of the Milky Way. In all, tiny NGC 6520 holds 60 stars within a 6' area."

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "9M; 5' diameter; small and dense; 25-plus 9 thru 12M members; DK NEB B-86 on W edge; cluster N6540 is 30' due E."

Steve Coe

Steve Coe, observing with a 13" f/5.6, notes: "Pretty bright, pretty large, pretty rich, compressed, 22 members at 165X. There is a nice orange star in the center. Dark nebula B86 is distinct on the west side and the dark nebula and the cluster are about the same size."

Contemporary observations

Magda Streicher

(no date)

Alldays (22.50S, 20.12E, 770m).

12-inch f/10 SCT (95x, 218x)

The larger part of this cluster forms a tight round inner section 3', which displays a round figure with faint stars. In a way it reminds me of a buffolo with his hornes, both hornes going west one from the north the other from the south extending away from this grouping.

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Lacaille's catalogue

The Messier objects

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