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RA: 01h 33m 24s
Dec: +60° 39′ 24″
Ch: MSA:48, U2:37, SA:1
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 22m
Mag: B=7.72, V=7.4
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In the Appendix to the 1912 'Scientific Papers of Sir William Herschel' this object is described as "1783, August 8. 14 or 16 pretty large stars with a great many eS ones. Two of the large ones are double, one of the 1st the other of the 2nd class. The compound eye glass shews a few more that may be taken into the cluster so as to make about 20. I exclude a good many straggling ones, otherwise there would be no knowing where to stop."
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "beautiful field, 1 degree following and a little north of Delta Cas, containing Struve 131, and a red star."
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: "Circular, well-defined. 3' from the centre, diametrically opposed, lie 2 *, vB in comparison with the other * of this cl."
Journal BAA, 35, p159
Contains 2 B * diametrically opposuied, abut 6' apart, which appear to be giants in comparison with the other stars of the cluster.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
"M103; diam 5; cluster, coarse."
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Remarks, p.217: "This cluster contains one bright star, +59°271, whose photometric mag is 7.26."
Trumpler (Lick Obs Bulletin, Vol 14, No. 420) gives the diameter as 6.5' and the class as II 3 m.
The RNGC (Sulentic and Tifft 1973) notes that this is a 7.0 mag open cluster.
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 7.56.
Phelps and Janes give the outer cluster radius as 4.62arcminutes and list the minimum number of cluster members as . 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.]
MacRobert says it has "glimmering starry depths behind a few bright luminaries." It contains a bright star on one edge, the double Struve 131.
Sanford says that the cluster contains about 40 stars in an area 6' across.
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "7.4M; 6' diameter; arrowhead shape with bright star at NNW point; OPN CL Tr-1 is 35' to NNE."
This cluster lies about one degree northeast of Delta Cas. Harrington writes: "M103 holds a footnote in astronomical history as being the final object listed in Charles Messier's original catalogue." Messier described it as simply "a cluster of stars." Harrington continues: "As seen with modern telescopes, M103 has a luster that Messier could never have imagined with his comparatively poor instruments. Today's amateurs record it as a sparkling arrowhead of stardust about 6' across. Marking the tip is the attractive multiple star Struve 131. there are actually five stars here, but many amateur telescopes show only the 7.3 mag primary accompanied by 10.5 and 10.8 mag companions separated from it by 14 and 28 arcseconds, both to the southeast. ... Of the more than 25 true members of M103, the brightest is a 10.6 mag blue-white orb. Many of the other stars display subtle hints of colour, especially when the telescope is slightly defocused. Perhaps the most noticeable is an orange 9th mag star lying just southeast of the cluster's centre."
Observer: William L. Schart
Your skills: Intermediate (some years)
Date/time of observation: 8/24/98 11:24 pm CDT
Location of site: Killeen, TX (Lat 319 5s, Elev 600ft)
Site classification: Suburban
Sky darkness: 4 Limiting magnitude
Seeing: 7 1-10 Seeing Scale (10 best)
Moon presence: None - moon not in sky
Instrument: 6" Orion Dobsonian
Magnification: 48x, 70X, 120x
I counted 15 stars visible to me. Four were brighter, the rest faint. Triangular shaped.
Hoag: 30cm red * V=8.5.
6cm - 50x/80x in dk sky: 13 *s w/in triangle. br * on NW. cl elong SE-NW. a little haze, two brtr *s in cl.
7cm - consp @ 30x w/many *s res btwn two br ones. 75x: 25 *s total in triangular outline. BS, 25Nov1992, Anderson Mesa.
8cm - sm, not consp @ 20x. br * on N, a few others res on periphery. BS, 17Oct1982, Anderson Mesa.
15cm - sm cl w/four br *s. ten fntr ones m11.5+. 7' diam. BS, 25Oct1970, FtL.
- nice fairly br cl inside triangle formed by m6 * NNW, m7 * SE, and m10 * SSW. 7' diam w/60 *s m10+, except for the two brtr ones, and two others. broad concen. BS, 10Dec1990, Anderson Mesa.
20cm - fairly br and triangular in shape. a few br * forming outline w/fntr *s inside. 50 *s in 7' area. good @ 125x.
25cm - mod br in triangle of *s. 6' diam w/30 *s.
30cm - mod compact, 8' diam w/m9.5 * on NW side. another SE outside of cl. 50 *s w/many threshold ones not counted. SE of center is vred m10.5 *.
Observing site: Little Tycho Observatory
[1h 33m 12s, 60° 42m 0s] AKA M 103. A cluster of ~50 faint stars and 10 bright ones. A triangle of 9mv stars frames the cluster. Lovely.
The Messier objects
The Bennett objects
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