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RA: 21h 45m 9s
Dec: +65° 46′ 30″
Ch: MSA:1060, U2:33, SA:3
Ref: SIMBAD, DAML02, Archinal&Hynes (2003)
Type: open cluster, 12r
Mag: B=10.36, V=9.3
Synonyms: H VII-066
Discovered in 1794 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a cluster of considerably compressed vS and large stars, about 12' diameter."
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
p.178: "Six clusters noted in Lick Obs. Bull., No.219 (Descriptions of 132 Nebulae and Clusters photographed with the Crossley Reflector) are not included in the catalogue.
NGC 7142: Clustering of faint stars in a rich region, not well defined. Diameter 15'. Might possibly be included in Class III [loose clusters, often of a few stars only, and of irregular outline]
(Lick Obs Bul, Vol 14, No. 420) gives the diameter as 11' and the class as 2 1 m.
(Sulentic and Tifft 1973) notes that this is a 10.0 mag open cluster.
Phelps, R. L., Janes, K. A. & Montgomery, K. A. (1994) Development of the galactic disk: A search for the oldest open clusters. Astron.J., 107(3), 1079.
Included in Table 6: The oldest open clusters.
by Jim Lucyk: Sky&Tel. 10/74 p265.
described as "Some 35 stars were counted, a nice cluster resembling a rectangle. 6-inch, 35x."
Hoag et al: cl *s m12+.
15cm - mod f cl of f *s consp @ 50x. 80x/140x: 12' diam, extending past three
m10-11 *s in NE quad. 140x shows about 50 *s w/o difficulty, but as
many more @ threshold not easy to count. little concen. brtst *s m13.5
or so---lots of 'em at same brtness, prob the red-giant clump. dbl * E:
sep ~2", dm 0.15, just recog @ 80x. BS, 8Sep1991, Anderson Mesa.
25cm - 90x: 12' diam cloud. irreg round. *s m11.5+, 35 *s counted. no cen
condens and w/o sharp boundaries.
30cm - spread and unconcen. 35-40 *s in 11'+ diam. all *s, except three br
ones, are m13+. fairly uniform in brightness & distribution. three br
*s are N, E, & SE. irreg round.
Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "10M; 10' diameter; 50-plus 11M and dimmer members; rich and compressed group; planetary N7139 (13.3M; 80" diameter) 2 degrees due S of center; soft and faint; no center star visible; use N-filter; 20' to NW is DIF NEB N7129."
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