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RA: 19h 43m 10s
Dec: +23° 17′ 54″
Ch: MSA:1195, U2:162, SA:8
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 13mn
Mag: B=7.71, V=7.1
Synonyms: H VII-018
Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "an extended cluster of irregularly scattered stars of various sizes, considerably rich."
(Lick Obs Bul, Vol 14, No. 420) gives the diameter as 7' and the class as 4 3 p.
(Astrophysical Journal Supplement, No 105, 1965) in her Catalogue of Bright Nebulae notes that this isolated nebula is moderately bright, more prominent on the red POSS plate and has a maximum size of 40' x 30'. It is a member of the Vulpecula OB 1 Association.
The RNGC (Sulentic and Tifft 1973) notes that this is a 10.0 mag cluster associated with nebulosity.
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
by Jim Lucyk: Deep Sky #11 Su85 p9, Deep Sky Monthly 9/80 p14, Deep Sky #23 Su88 p41.
Notes: "NGC 6823 offers little other than half a dozen stars of magnitude 9 and 10 over a 5' area. The eye is attracted by three conspicuous stars in a row that is less than 1' long."
Houston notes this cluster is about 12' diameter but "has half again as many stars as NGC 6830 [which has about 20.] A quick search through my records turned up several amateur observations of the cluster but no mention of the surrounding diffuse nebulosity..."
Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "10M; 5' diameter; 30-plus 11 thru 12M members; surrounded by faint nebulosity with the designation N6820 (20' diameter); small cluster N6830 (9M; 8' diameter) 1.5 degrees due E."
WDS: trapezium = ADS 12828 + Pourteau 4026/27/28: V=9.3,11.0,11.1,10.0
(going E to W), farthest are 18".4 apart, pa307. see Skiff article in Deep Sky
8cm - pretty well concen in center, but other *s scattered @ 20x. BS, 15Sep1982, Anderson Mesa.
15cm - diamond noted. 15 *s.
- general aspect sim to I4996 in Cyg at 50x, but surrounding fld not so dense and cl is lgr and has more brtr *s. 5' diam w/30 *s incl central trapezium. 165x shows trap well but only occas glimpses of other inv comps---just too faint for this aperture! BS, 26Mar1988, Anderson Mesa.
- can just see f triangle *s nr Nrn * of trap @ 295x. also at least one * S of middle pair twd Srn *. BS, 5Sep1989, Anderson Mesa.
25cm - 5' diam, 35 *s. diamond in center. br *s 10' S and 5' NW.
30cm - 30 *s m8-12. loose.
Alldays (22.50S, 20.12E, 770m).
12-inch f/10 SCT (95x, 218x)
The petite cluster is round in shape and stringe towards the NW. The middle section seems tight with double stars. The soft cloud around it is seen with a 0111 filter, which the slightly more prominent nebulosity towards the south of the cluster.
16-inch f/10 SCT (95x, 127x)
My notes indicate a most petite middle in the formation of the stars. The focus is a knot of four faint stars in the middle from where it works it way outwards more loosely and more so to the west. Knowing that it is surrounds by a nebula I use the 0111 nebula to see very faint nebulosity to the NE of the cluster.
The Messier objects
The Bennett objects
The Caldwell list
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