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RA: 02h 22m 5s
Dec: +57° 07′ 48″
Ch: MSA:46, U2:37, SA:1
Ref: SIMBAD, DAML02, Archinal&Hynes (2003)
Type: open cluster, 13r
Mag: B=6.58, V=6.1
Synonyms: H VI-034
Recorded on November 1, 1788 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a very beautiful, brilliant cluster of large stars, irregularly round, very rich, near half a degree in diameter."
An observer using the 72-inch f/8.8 speculum telescope at Birr Castle noted "Sept 13, 1850. Between the two clusters there is a red star nearer the second, and 2 more red stars following the second cluster, of 8th or 9th mag."
The more easterly component of the famous Double Cluster in Perseus. Burnham speaks of it as a "wonderfully beautiful object" and "most impressive and spectacular." Olcott spoke of the Double Cluster as a field "simply sown with scintillating stars, and the contrasting colours are very beautiful." The NGC describes it as remarkable, very large and very rich with a ruby star in the middle. Espin in 1892 listed three M-type red supergiant stars in this cluster, none in NGC 869 and four lying between the clusters. Blanco's 1955 list contained 17 such stars ranging from magnitude 7.6 to 9.2. The existence of these clusters was noted at least as far back as 150BC, and Burnham notes that Hipparchus and Ptolemy mention the group, but refer to it as a "nebula" or "cloudy spot". Burnham further wonders why it was not included by Messier in his famous catalogue, who included other bright clusters such as the Pleiades and Praesepe.
Trumpler (Lick Obs Bulletin, Vol 14, No. 420) gives the diameter as 30' and the class as 4 3 r
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Based of F-A plates: "The densest accumulation of the stars lies somewhat eccentrically. The form more regular than NGC 869. Besides, a fairly equal distribution of the stars."
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
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.
"! cluster, fairly condensed."
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Vorontsov-Velyaminov, B. (1925) "Catalogue of integrated magnitudes of star clusters", Astron. Nach. 226.195. Comparing the brightness of the cluster with the extrafocal images of stars, he estimates the magnitude as 4.90.
The RNGC (Sulentic and Tifft 1973) notes that this is a 4.5 mag open cluster.
Harrington writes: "Even the smallest glass will begin to unleash the beauty of the Double Cluster. . . As seen with 11x80 binoculars, the clusters took on a fiery radiance against the star-filled backdrop. For the first time with binoculars I could make out a few stars shining with subtle hues of yellow and red scattered throughout a field dominated by blue-white suns."
Mullaney writes: "Contrasting colours are evident in 4-inch and larger instruments, and the outer edges of the clusters overlap."
John Bortle (Webb Society Quarterly Journal, January 1976) using 10x50 binoculars, estimates the visual magnitude as 3.3.
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "4.4M; 20' diameter; 150-plus 8M and dimmer members; E half of the "DOUBLE CLUSTER"; both visible in 1 degree field; STUNNING!."
The Messier objects
The Bennett objects
The Caldwell list
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