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RA: 13h 42m 11.23s
Dec: +28° 22′ 31.6″
Con: Canes Venatici
Ch: MSA:651, U2:110, SA:7
Ref: SIMBAD, SEDS
Type: globular cluster
Mag: B=?, V=6.2
In the Philosophical Transactions, 1814, William Herschel wrote "September 24, 1810. Large 10 feet Newtonian telescope. Magnifying powers 71, 108, 171, 220. The 3rd of the Connoissance des Temps is one of the globular clusters; very brilliant and beautiful. The compression of the stars begins to increase pretty suddenly from the outside at 3/4 of the radius, and continues gradually up to the centre, its diameter in the outside is full half of the field of the glass magnifying 171 times, which gives 4' 30 seconds." In the Philosophical Transactions, 1818, William Herschel wrote: "1813, 7 feet finder. It is at a small distance from a star of equal brightness, the star is clear, the object is hazy, and somewhat larger than the star. 1783, 7 feet telescope. With 460 power the light is so feeble that the object can hardly be seen; I suspect some stars in it. 1813, with 80 power, many stars are visible in it. 1799, 10 feet telescope, power 120; with an aperture of 4 inches it is resolvable, with 5 easily resolvable, with 6 it is resolved; with 7 and all open the stars may be easily perceived. 1784, 1785, 20 feet telescope. A beautiful globular cluster of stars, about 5 or 6' in diameter. 1810, large 10 feet telescope, with 171 power the diameter is full 4' 30 seconds."
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "a brilliant and beautiful globular congregation of not less than 1000 small stars. Smyth, blazing splendidly, that is, running up into a confused brilliancy towards the centre, with many outliers. 3.7-inch hardly resolved it. Buffham centrally resolved 9-inch reflector; sprinkled over and surrounded by the larger stars, and resolved with 9.5-inch speculum. In a triangle of stars, rather nearer Arcturus than Cor Caroli."
Burnham calls it a "superb object", describing it as a "beautiful bright globular cluster, one of the most splendid in the sky. It was discovered by Messier in 1764 and can be seen as a hazy 6th magnitude 'star' in field glasses. The small telescope shows it as a round nebulous object about 10' in diameter ... at least a four-inch telescope is needed to partially resolve the outer edges, and a good 6-inch glass with a fairly high power will reveal hundreds of stellar points. Large telescopes show an incredible swarm of countless star images, massing to a wonderful central blaze, with glittering streams of stars running out on all sides. The seeming arrangement of the outer members into radiating streams and branches was noticed by both the Herschels and Lord Rosse [Admiral Smythe mentions the strings of stars at the outer edge of the cluster. He also notes that the cluster has a curious resemblance to a jellyfish.] ... Lord Rosse found several small dark obscuring patches in the central mass, more or less verified on modern photographs [some of which appear on photographs taken with the 120" reflector at Lick Observatory], but more definitely present in the Hercules system M13. ... M3 contains many thousands of stars, from magnitude 11 or so to the limit of detectability. ... At Palomar Observatory, more than 45,000 stars have been counted in this cluster, down to magnitude 22.5."
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
The RNGC (Sulentic and Tifft 1973) notes that this is a 7.0 mag globular cluster.
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.
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 6.95.
"!! globular cluster, condensed"
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Remarks, p.217: "a small globular cluster, containing, nevertheless, not far from 5000 stars. 132 of the brighter ones are known to be variable. the stars appear to be divided into two groups, one having stars from the 13th to the 15th magnitudes, and the other, very faint stars of about the 17th magnitude.."
Hartung notes that "this beautiful object can be plainly resolved with 10.5cm and even 7.5cm will show a few faint outliers. It is very bright, round and symmetrical, and sparkles with innumerable starry points right to the broad centre 3' across while the outliers extend to 7' and probably are thinly scattered much further."
Houston notes: "In a 10-inch, its edges break down into glittering stars, some of which may show even in the bright central blaze. Unlike M13 in Hercules, M3 does not seem to have strings of stars trailing outward."
Sanford notes that it should show in a finder scope as a fuzzy 6th mag star. He continues: "M3 begins to resolve in a 6-inch telescope: in a telescope of twice that aperture, it will appear as a ball of glittering points."
John Bortle (Webb Society Quarterly Journal, January 1976) using 10x50 binoculars, estimates the visual magnitude as 6.3.
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "6M; 18' diameter; extremely bright and large! well-resolved, rich and compressed beauty; rivals M-13 with its 11M and dimmer stars."
Observer: Alan Shaffer (e-mail: email@example.com, web: http://www.geocities.com/CapeCanaveral/3693/)
Instrument: 10-inch Schmidt-Cassegrain reflector Location: Redondo Beach, California, US
Light pollution: severe Transparency: good Seeing: fair
Time: Fri Apr 11 16:30:00 1997 UT Obs. no.: 117
Very large. Easy to spot even under poor conditions. Used 24.5mm SWA at f/10 for 104X. The field is VERY large and concentrated at the middle. Total field is @ 10 minutes of arc.
Harrington, P. (1986) More globulars for observers. Sky&Telescope, Sep, 310.
Todays 6-inch will reveal a moderately compressed nucleus surrounded by hundreds of stars. A 12inch will show stars across its entire face. Many observers.. have noted star chains formed by the clusters outer suns.
Adam Albino (IAAC)
Your skills: Intermediate (some years)
Site classification: Exurban
Sky darkness: 5.2 Limiting magnitude
Seeing: 7 1-10 Seeing Scale (10 best)
Moon presence: None - moon not in sky
Next to M-13, I think this is the finest GC. Very large, Resolved to the core starting at around 120X. 80mm could not really resolve it fully. Seen noticeably well even in my 7x50 finder. This is a must object with bino's of any size.
RA 13 42 11.2 (2000) Dec +28 22 32 Integrated V magnitude 6.19 Central surface brightness, V magnitudes per square arcsecond 16.34 Integrated spectral type F6- Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.85 Core radius in arcmin .50. ["Catalog Of Parameters For Milky Way Globular Clusters", compiled by William E. Harris, McMaster University. (Revised: May 15, 1997; from http://www.physics.mcmaster.ca/Globular.html; Harris, W.E. 1996, AJ, 112, 1487) ]
= M 3
POSS: the two *s in 1988 15cm obs are 2'.2 apart. m10.5 * 10'.0 NNE.
L&S chart: 7cm * on W edge V=12.7.
naked eye - like f dbl *, w/cl as NE comp. BS, 29Apr1992, TSP.
7x35mm - br strongly concen spot reaches about 2/3 way to m8 * SE; brtr * SW. cl center *ar. BS, 29Apr1992, TSP.
6cm - pretty well concen w/extensive halo and sm core. in dk sky.
7cm - br cl @ 30x, vfinely-grained texture. 75x: just at grainy-to-part-res border. halo reaches 1/2 way to m9 * NW, core 1/4 this. consp m12 * just w/in W boundary. m12.8 L&S chart * vis @ 75x well outside halo. BS, 12Apr1993, Anderson Mesa.
15cm - big & br. somewhat oval shape noticed. 38x: gran. 76x/137x: res just attainable w/some *s standing out. 152x/203x show an amazing array of hundreds of *s in curved rays and cen spot. HM/BS, 1Jan1971, FtL.
- partially res @ 80x and up. outliers to 18', as far as m10.5 * NNE. brtr part 9' across; core 2'.5 across, viz distance btwn m9.9 * NNW and m12.8 * S of it (cf L&S chart). BS, 20May1988, Anderson Mesa.
25cm - quite elliptical at lox. vbr core w/*s nrby. 112x resolves outliers. 179x res almost to cen w/vbr oval nuc; core surrounded by overall squarish form. cen blaze W of center.
- elong SE-NW, 10'x8'. brtst area 2'.5 across. well res. 180x/240x.
- in dk sky outliers extend to 20' diam. core 4'-5' across w/consp * nr center.
Danie Cronje, observing with 10x50 binoculars, calls it "Bright. Centre slightly extended and very bright. Overall cluster doesn't seem very large."
Ed Finlay, observing with 10x50 binoculars from Johannesburg, 1992 May 17, calls it "a barely discernable fuzzy point of light; 6th mag in the binoculars. Needs a larger aperture to view properly."
1992 May 27: "definite identification as Canes Venatici much higher in sky. M3 now a very faint but discernable fuzz ball."
1993 May 24, Meade 4-inch ED APO refractor: "At last could see this globular cluster without much trouble. Mag 63. About 16.2 arc mins diameter. Faint fuzzy cloud like M4. My 10x50 binoculars gather 64x more light than the naked eye. The 4-inch refractor 256x which is 192x more light that the binoculars. This difference is certainly discernable at the eyepiece and makes for much more interesting and rewarding viewing."
12-inch f/10 SCT (95x/52.8′, 218x/23.1′)
Like all globular clusters there is something unique to them. M3 displays a very dense core more or less 1' in size, which is on the verge of resolving into starlight. However from this compact, bright-unresolved core, starlight became visible and multiplies along to the edges. It blazes off with outliers and pinpoint stars scattered around the flimsy edges of the cluster. The southwestern side of the globular is busier with star strings that spray out into the field of view. A triple star on the south east of the globular keeps coming back into my eye's view.
Observing site: Little Tycho Observatory
[13h 42m 12s, 28° 23m 0s] Very nice, even in the light pollution.
Observing site: Little Tycho Observatory
[13h 42m 12s, 28° 23m 0s] A glittering sphere of stars, surrounded by haze with direct vision, a spangled globe with averted vision.
The Messier objects
The Bennett objects
The Caldwell list
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