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NGC 6645 (15,194 of 18,816)

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NGC 6645

NGC 6645, Cl Collinder 383, C 1829-169, VI 23, h 2013, GC 4416

RA: 18h 32m 36s
Dec: −16° 54′ 0″

Con: Sagittarius
Ch: MSA:1367, U2:295, SA:16

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

(reference key)

Type: open cluster, 41m

Mag: B=?, V=8.5

Size: 14′
PA: ?

Historical observations

William Herschel (c.1784)

Synonyms: H VI-023

Discovered in 1786 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a beautiful cluster of vS stars of various sizes, 15' diameter, very rich."

Published comments

Trumpler, R.J. (1928)

Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 13' and the class as 1 2 r.

Melotte, P.J. (1915)

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

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 8.5 mag open cluster.

Photo index

Photo Index by Jim Lucyk: Burnhams V3 p1595.

Bailey, S.I. (1908)

"cluster, fairly condensed"

Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.

Modern observations

Harrington, Phil

Harrington writes: "It's a striking group of faint stars sprinkled across 15' of sky. The brightest of the 40 or so members in this cluster are 11th mag, making resolution difficult in scopes smaller than 4 inches. Larger instruments reveal a dense stellar swarm floating in a rich field of starlight. Two arcs of stars extend from either side of the cluster's round core, painting in my mind a picture of a bird in flight."

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "9M; 10' diameter; fairly large, rich and compressed; 75-plus 11 thru 15M members."

Steve Coe

Steve Coe, observing with a 13" f/5.6, notes: "Bright, large, rich, pretty compressed, 49 stars counted at 100X. This cluster is in a bizarre "donut" shape with no stars in the center of this grouping. There are lots of dim members."

Contemporary observations

Auke Slotegraaf

1995 June 01

1995-06-01: 11x80. Kelsey Farm. 23:00 SAST. A quite apparent, puffy affair, maybe one or two 9th mag stars involved. Appears roughly triangular. Running almost due east - only slightly south - for over half a degree is a neat row of five unequal stars. The wispy cluster seems to be attached to this row, and together they look like a tassled fly chaser or maybe a worn-out feather duster.

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