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NGC 6633 (15,143 of 18,816)


oc gc pln bn dn gx gxcl ast aka lost




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NGC 6633

NGC 6633, Cl Collinder 380, C 1825+065, COCD 446, VIII 72, GC 4410

RA: 18h 27m 31.2s
Dec: +06° 34′ 12″

Con: Ophiuchus
Ch: MSA:1271, U2:205, SA:15

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

(reference key)

Type: open cluster, 32m

Mag: B=5.01, V=4.6

Size: 20′
PA: ?

Image gallery

Photos  (1)

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Historical observations


Discovered by Caroline Herschel.

William Herschel (c.1784)

Synonyms: H VIII-072

Noted in 1788 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a cluster of coarsely scattered large stars. Caroline Herschel discovered it in 1783."

Published comments

Trumpler, R.J. (1928)

Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 25' and the class as 1 2 pE.

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 5.5 mag open cluster.

Doig, P. (1925)

Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part IV. M.N.R.A.S., 36(2), 58.

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.

Bailey, S.I. (1908)

"cluster, coarse"

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

Doig, P. (1926)

"A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.

"irregaulr cluster of bright stars; contains long period variable T. Serpentarii." He gives the approx. diameter as 28 arcmin.

Melotte, P.J. (1915)

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

Photo index

Photo Index by Jim Lucyk: Burnhams V2 p1265, Deep Sky #23 Su88 p25.

Modern observations

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "5M; 20' diameter; bright, large and sparse; 65-plus 7M members; bright star just S and a bit E is 5.5M SAO 123516."

Steve Coe

Steve Coe, using a 13" f/5.6, notes: "Bright, large, not compressed, pretty rich at 60X. This nice cluster is easy in the 11 X 80 finder, with many bright members, sevral are yellow or light orange in color. I counted 38 stars in this lovely cluster. 13" 60X--bright, large, stars 8..., little compressed, pretty rich, several nice chains of stars, 32* counted. Several stars show color, 2 blue and 3 yellow in cluster. A very rich field."

Gross, Todd (IAAC)

Observer: Todd Gross

Your skill: Intermediate - Many years

Date and UT of observation: 3/09/99 09:15 GMT

Location & latitude: 22 mi. West of Boston, Ma. 42.3N

Site classification: Suburban

Limiting magnitude (visual): approx. 4.7 zenith

Seeing (1 to 10 - worst-best): about 3

Moon up (phase?): Yes, last 1/4 (just over)

Weather: Crystal Clear

Instrument: C9.25" SCT f/10 f.l.2350

Magnifications: 123 & 87x

Filters used: none

Object: NGC6633

Constellations: Ophiuchus

Object data: Open cluster

Size(s): 27'

Position: 18:28 +6:34

Magnitude: 4.6

Personal "rating" (at this aperture, and sky condition): B/B-

Large, loose cluster, fairly bright stars, mostly of the same magnitude, randomly distributed. Pretty, but required even lower power for a better view.



Boston Meteorologist Todd Gross

Contemporary observations

Magda Streicher

(no date)

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

12-inch f/10 SCT (95x)

The first object was NGC 6633 in Ophuichus, with the constellation already descending in the West. My first impression revealed a bright grouping of stars of various magnitudes. The centre exhibited a few brighter stars in the shape of a semi-circle, along with a faint uneven string of stars to the east that drapes from North to South. Concluding the observation was a very tight group of six stars to the west.

Auke Slotegraaf

1997 July 07

1997 July 7, Monday, 21:00 - 24:00 Jonkershoek. 11x80's tripod-mounted. About 12 8th magnitude stars in an elongated (1:3) and narrowing rectangle. Bright star to the south-east. At the north-western edge of the cluster is a dark area; the rectangle of stars, plus other stars in the milk way field to the north-west, together make a much larger irregular scattered cluster, about 45' across, with a round, black hole in the centre! Quite remarkable!

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