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RA: 01h 19m 31s
Dec: +58° 17′ 0″
Ch: MSA:48, U2:36, SA:1
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 23r
Mag: B=6.97, V=6.4
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Synonyms: H VII-042
Discovered in 1787 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a brilliant cluster of large and vS stars, considerably rich."
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "a very elegant group attending Phi,5th mag. The second star lilac. Red star 30' north, a little following Phi."
(Lick Obs Bulletin, Vol 14, No. 420) gives the diameter as 12' and the class as I 3 r.
give the outer cluster radius as 6.22arcminutes and list the minimum number of cluster members as 588. They include a plotted image of the cluster. [Phelps, R. L. & Janes, K. A. (1994) "Young Open Clusters as Probes of the Star Formation Process. 1. An atlas of open cluster photometry" Astrophys. J. Suppl. Series, 90:31-82.]
by Jim Lucyk: Sky&Tel. 3/71 p178, Sky&Tel. 11/81 p509, Astronomy mag. 2/86 p65, Deep Sky #8 Fa84 p22-23, Deep Sky #6 Sp84 p25, Deep Sky Monthly 9/80 p13, Burnhams V1 p531, Vehrenberg's Atlas of DS Splendors (3ed) p31.
Doig, P. (1926) "A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.
"Small circular cluster, strongly condensed." He gives the approx. diameter as 14 arcmin.
Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part I. M.N.R.A.S., 35(5), 159.
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Based of F-A plates: "Contains a tolerable num of middle-bright * strongly condensed, The form rather dircular, yet a couple of offshoots."
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
The RNGC (Sulentic and Tifft 1973) notes that this is a 8.0 mag open cluster.
Burnham calls it a "bright .. cluster located in the rich star fields of the Cassiopeia Milky Way, about four degrees southeast of Gamma Cass. It is a rich scattered group of stellar points, some 10' in diameter, containing about 100 stars brighter than 13th magnitude. Some 60 of these are presently identified as true cluster members ... in the main mass of the cluster, the brightest star is a red supergiant if type M0, of apparent magnitude 8.6 ... the bright star Phi Cassiopeiae, mag 5.0, spectrum F0, is of special interest from its position on the southeast edge of the cluster. If actually a member, this star .. must be one of the most luminous of all known stars." Burnham notes that at the distance to this cluster, our Sun would appear as a star of magnitude 17.3!
Houston calls it a coarse group of bright stars with the 5th mag Phi Cas at its edge. About 50 stars can be seen with a 6-inch at 80x. He suggests you look about 40' northwest for NGC 436,a smaller cluster of fainter stars.
Harrington calls this cluster "a delight to observe through all optical instruments. It is home to some 80 stars, many of which are obvious through even the smallest backyard telescopes. What is especially fun about NGC 457 is its distinctive shape. One glance and you're likely to see why it's known as the Owl cluster. A dozen or so stars of magnitudes 9 to 11 form the bird's body, with a pair of 10th mag suns marking the tail feathers to the northwest. Two arcs, each containing about a half dozen stars, form the wings. The east wing is highlighted by a distinctive 8th mag ornage star, the brightest true member of the cluster. But what draws immediate attention are the owl's dazzling eyes, marked by the 5th mag Phi Cassiopeiae and 7th mag HD 7902. Although both are probably foreground stars unrelated to the cluster, their presence adds to the drama of this outstanding group."
Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "6.4M; 10' diameter; includes 5M Phi CAS; 100-plus members; the "ET CLUSTER" (ET waves his arms at you, and winks!); a.k.a. the "OWL"."
described as "some 50 stars counted in this large cluster of prominent bright stars. Resembling some type of bug! 8-inch, 48x."
With a 6-inch the group does look like a gangly humanoid figure with arms splayed out and brilliant, unequal eyes far apart. He has a red star in his north armpit. The inner part of the cluster, ET's body, looks like a long, hollow arrowhead pointing northwest, says Alan M. MacRobert.
WDS: phi-1,2 Cas = ADS 1073. pair NW = Stein 1560 [0113.1+5747, BD+57 247]: V=9.8,10.1 (Pesch); 13".5; 319 (1911). closer pair (1990 15cm obs) = WDS0113.3+5746: V=11.04/0.27,11.35:/0.30 (Pesch); 8".0; 178 (1914) sl different mags in Hoag and in Jones & Hoag. wide pair SE in this grp not in WDS (not sure), brtr * V=10.81/0.26.
CBL: mandate : 15cm can see at least 45 *s. [1990: is 150 enough?]
7cm - nice br cl @ 30x, where Eicher `Owl' stands out well. 50x: 20' diam with 50 *s strongly concen twd center. roughly equal pair [Stein 1560] nr intersec of figure's `wings' and `body' consp as is sm triangle to SE in neck twd phi1,2 Cas. BS, 25Nov1992, Anderson Mesa.
8cm - nice @ 20x, Eicher's `Owl' obvious: phi-1,2 are its eyes, bird flies SE. 25 *s res in figure w/mod concen. phi-1,2 are yel & bl. BS, 17Oct1982, Anderson Mesa.
15cm - wow! impressive. two brtr *s on SE side w/1' sep, m7 [phi-1,2 Cas]. 25 *s m10+ in 15' diam. BS, 25Oct1970, FtL.
- nice rich cl rich in fntr *s, but many brtr ones also. Eicher's `Owl' figure flies SE (`eyes' are phi-1,2 Cas). looks good @ 50x in 1.2-deg fld. overall diam of figure 20', main body of cl only 10'. 140x shows 150 *s in this smlr area. where `wings' join body of Owl are three pairs: one close, two wide. BS, 26Sep1990, Anderson Mesa.
20cm - brilliant @ 62x. yel m4 * on S side [phi-1 Cas]. irreg round w/100 *s m9+ in 20' area @ 125x. nice. FtL.
25cm - vbr and fine @ 90x. triangular shape. phi-1,2 Cas are yel & bl. south-center has condens of br *s. north-center has well-def dk patch. N edge has red m9 * [V466 Cas?].
30cm - 15' diam. SE is m7 *. mod concen grp of m7.5 *s. on NW side is m9.5 pair: 30"; pa320. many threshold *s.
Observing site: Little Tycho Observatory
[1h 19m 6s, 58° 20m 0s] A grand cluster of ~80 stars, many of them appear to be double, and many are quite blue.
The Messier objects
The Bennett objects
The Caldwell list
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