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RA: 19h 51m 0s
Dec: +23° 06′ 0″
Ch: MSA:1195, U2:162, SA:8
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 22p
Mag: B=8.41, V=7.9
Synonyms: H VII-009
Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a large cluster of pretty compressed stars most of one size."
Roslund, C. (1960) Remarks on Some New and Some Known Galactic Clusters. PASP, 72(426), 205. [1960PASP...72..205R]
"The brightest star is of type A1 II, followed by a B8 II-III star and middle and late B stars on the main sequence."
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 10' and the class as 4 2 m.
The RNGC (Sulentic and Tifft 1973) notes that this is a 9.0 mag open cluster.
Photo Index by Jim Lucyk: Vehrenberg's Atlas of DS Splendors (3ed) p207, 213.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Observer: Michael Geldorp Your skills: Intermediate (some years) Date/time of observation: 10/13/1999 19.25 UT Location of site: Alphen ad Rijn, Netherlands (Lat 52.09N, Elev ) Site classification: Suburban Sky darkness: 4.5 Limiting magnitude Seeing: III I-V Seeing Scale (I best) Moon presence: None - moon not in sky Instrument: 8" F/6 Dobsonian Magnification: 49X, 98X, 203X, 244X Filter(s): none Object(s): NGC 6830 Category: Open cluster. Class: Constellation: Vul Data: mag 7.9 size 12'.0 Position: RA 19:51 DEC +23:04
Description: Little cluster in a rich starfield. Formed just like a cross in a cross. About a dozen star were resolved in the inner portions. At 203X many stars were seen at the threshold ob visibility. Hard to tell were the cluster ends and the milky way resumes.
There is a sketch on this object on my homepage -- Optional related URLs: http://home.wxs.nl/~geldo006/home.html
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "9M; 8' diameter; fairly tight group of 20-plus 11M and dimmer members; 0.5 degree N of 5M 12 VUL."
Houston notes that large binoculars are adequate for this cluster. Its brightest stars are magnitude 9, and in all there are perhaps a score brighter than 13, over an area 8' across.
Houston notes that a 10-inch should show this 8th mag cluster as having about 20 stars spread over 12'. He writes: "The cluster is also an interesting binocular object that is surprisingly easy to locate, considering the rather rich Milky Way background."
Hoag: brtst * nr center V=9.88/0.28.
8cm - easy @ 20x. sm, diffuse, but hisfcbr. gran to partially res. BS,
15Sep1982, Anderson Mesa.
15cm - 5' diam. brtst * on E, 15 *s like four-legged spider.
- mod f cl only mod-well detached from fld. 6' diam w/35 *s @ 140x. brtr
*s on E and some fntr ones on W form fairly consp X w/arms NE-SW and
NW-SE. brtst * m9.5 is first * SE of `cen *' of X. not well condensed
overall. from N edge of cl NEwd is rel dk area; S&W semicircle is rich
in m12-14 *s. BS, 5Sep1989, Anderson Mesa.
16-inch f/10 SCT (127x)
Field scattered with cluster member in a multitude of magnitude stars. Middle part of the cluster shows of a distinctive cross shape that flares out in the busier northern section of the field. Faint members spray out quite far into the western part of the field. An asterism of brighter stars within the cluster standing out relatively prominent towards the east.
16-inch f/10 SCT (95x, 127x)
The cluster is medium rich in similar magnitude stars, and stand out in a nice way against the background star field. With care the stars form a letter X with the NW-SE bar the more outstanding. Star strings point out into the other direction NE-SW as well. I would say that the SW string is the more sparce bar. Two 9 and 9.5 Magnitude stars is situated just outside the SE cluster edge. The NE part is consist of the more fainter stars. Field scattered with cluster member in a multitude of magnitude stars. Middle part of the cluster shows of a distinctive cross shape that flares out in the busier northern section of the field. An asterism of a few stars within the cluster standing out relatively prominent towards the east.
The Messier objects
The Bennett objects
The Caldwell list
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