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RA: 03h 31m 36s
Dec: +37° 22′ 0″
Ch: MSA:119, U2:94, SA:4
Ref: SIMBAD, Collinder (1931), DAML02, NGC/IC, Archinal&Hynes (2003), Skiff20080430-s
Type: open cluster, 32m
Mag: B=7.35, V=6.7
Discovered in 1799 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a cluster of coarsely scattered large stars, about 15' diameter."
Observations with the 72-inch f/8.8 speculum telescope at Birr Castle noted "scattered cluster."
Trumpler (Lick Obs. Bulletin, Vol 14, No 420) gives the diameter as 15' and the class as 2 2 m.
The RNGC (Sulentic and Tifft 1973) notes that this is a 7.0 mag open cluster.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Doig, P. (1926) "A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.
"Loose cluster of about 60 stars." He gives the approx. diameter as 19 arcmin.
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
Listed by the Herschel Club, described as "loose, semi-poor, with 25 stars counted, slightly elongated in shape, large and scattered, stars bright in group. 6-inch, 48x."
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "6.7M; 15' diameter; irregular, sparse group; 50-plus 8M and dimmer members"
& Cr 40 & Mel 21 & OCL-401
03 31.6 +37 22
17.5: about 100 stars mag 9-14 in 15' diameter, scattered in chains and loops. Two mag 8 stars off the NE side are probably field stars, a nice double star is at the W end. There are several striking star lanes at low power including a long stream oriented E-W. A line of six stars oriented NW-SE forms the SW side and terminates at an easy double star. The NW end is near the striking double star (10.4/11.2 at 14". The field has a large variation of magnitudes.
8: bright, large, scattered, consists of mag 8 stars and fainter.
12-inch f/10 SCT (76x, 218x)
This is a unique cluster which show a lot of detail. Not only in its shape but also contain a dark part running out the cluster to the NW. The cluster stars shaped around this dark, reminds me of a octopus with the member showing a round shape towards the SE. This part is also busier, whereas the north western part contains two strings running along the dark part. It could also seen as a figure shape with the body and head to the SE and the legs to the NW.
Observing site: Little Tycho Observatory
[3h 31m 36s, 37° 20m 0s] A nice cluster of ~25 stars, 9-11mv. There is a bright yellow 6.5mv star around a degree (6 minutes, RA) east of the cluster not on the chart. (Perhaps just off of it?) WikiSky: The star is 7.3mv, and it is yellow.
The Messier objects
The Bennett objects
The Caldwell list
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