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NGC 6218 (13,965 of 18,816)

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Messier 12

NGC 6218, Cl Melotte 151, C 1644-018, GCl 46, Bennett 80, Messier 12, h 1971, GC 4238

RA: 16h 47m 14.52s
Dec: −01° 56′ 52.1″

Con: Ophiuchus
Ch: MSA:1300, U2:246, SA:15

Ref: SIMBAD, SEDS

(reference key)

Type: globular cluster

Mag: B=8.52, V=7.68

Size: 16′
PA: ?

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Photos  (2)

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Historical observations

William Herschel (c.1784)

In the Philosophical Transactions, 1818, William Herschel wrote: "1799, 10 feet finder. The object is visible in it. 1783, 1799, 10 feet telescope. With 120 and an aperture of 4 inches, easily resolvable; with 5 inches, stars become visible; with 6 inches, pretty distinctly visible; and will all open, the lowest power shows the stars. 1785, 1786, 20 feet telescope, a brilliant cluster, 7 or 8' in diameter, the most compressed parts about 2'."

Published comments

Bailey, S.I. (1913)

Bailey, examining a Bruce plate (Harvard Annals, Vol 72, No 2), describes it as "remarkable, bright, globular cluster, pretty compressed, several hundred stars, diameter 15'."

Vorontsov-Velyaminov, B. (1925/1926)

Vorontsov-Velyaminov, B. "Integral magnitudes of south star clusters", Astron. Nach. 228, 325. Comparing the brightness of the cluster with the extrafocal images of stars, he estimates the magnitudes as 7.15.

Melotte, P.J. (1915)

A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.

Doig, P. (1925)

Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part II. M.N.R.A.S., 35(8), 280.

Bailey, S.I. (1908)

"! globular cluster, fairly condensed"

Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.

Sulentic & Tifft (1973)

(Sulentic and Tifft 1973) notes that this is a 8.0 mag globular cluster.

Harris, W.E. (1997)

RA 16 47 14.5 (2000) Dec -01 56 52 Integrated V magnitude 6.70 Central surface brightness, V magnitudes per square arcsecond 18.17 Integrated spectral type F8 Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.38 Core radius in arcmin .66. ["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) ]

Modern observations

Harrington, Phil (1986)

Harrington, P. (1986) An observer's guide to globular clusters. Sky&Telescope, Aug, 198.

A 10inch scope will show stars across the whole disk. English observer Adm Smyth noted several bright 'spots' within the group, and lord Rosses teelscope in Ireland revealeed a possible 'spiral arrangement' of the stars.

Walter Scott Houston

Notes that this cluster resembles M10 in brighteness and diameter. In a 4-inch on a hazy night, it appeared about 7' across. The surface texture of M12 is patchy, as the eye seems to see some irregularities of brightness.

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "8M; 10' diameter; large, bright and round glow with many 11M and dimmer stars resolved against diffuse background; 10M star 3' SSE of center; GLOB M-10 is 3.1 degrees to SE; see both, together, in binoculars."

Bortle, John (1976)

Bortle (Webb Society Quarterly Journal, January 1976) using 10x50 binoculars, estimates the visual magnitude as 7.2.

Ware, Donald J

:"Lying only a few degrees away from M-10, this object is slightly smaller, about 8-10' in diameter. It is also well resolved across its face, and is somewhat looser than that object. It is basically circular and has a granular center."

Tomney, Jim (1997)

(e-mail: skytour@erols.com, web: http://users.aol.com/JTomney)

Instrument: 6-inch equatorial reflector Location: Marriotsville (Alpha Ridge), MD, USA

Light pollution: light Transparency: good Seeing: good

Time: Wed Jun 4 15:30:00 1997 UT Obs. no.: 157

I recall seeing M12 from my suburban (and more light polluted) backyard while doing the Messier list, but here at Alpha Ridge where the skies are noticeably darker I find that it is far more beautiful than I remember. It is a bit fainter than M10 but obvious when it slips into view at 28x. Even at this low magnification I can see that this is not your normal globular; it is loose in nature, uncertain whether it wants to fall into the Globular Cluster or dense Open Cluster camp. The field here is also a plus with many background stars. With the nice field and looseness of the globular it certainly brings M71 to mind, one of my all-time favorite globulars set amid rich Sagitta. The field stars boldly come right up to the object with maybe even one or two mingling as foreground points of light on the globular's periphery. The view at 75x is to be enjoyed as it accents the resolution better and still keeps a lively field. M12 seems to have a misty glow maybe about 5-7 arc-minutes wide, and there certainly does seem to be less of the mandatory symmetry characteristic of globulars. The 9.7mm gives a nice view but again tends to wash out this particular deep sky object.

Callender, John

(e-mail: jbc@west.net, web: http://www.west.net/~jbc/)

Instrument: 8-inch Dobsonian reflector Location: Carpinteria, CA, USA

Light pollution: light Transparency: good Seeing: excellent

Time: Sat Jul 12 08:10:00 1997 UT Obs. no.: 211

Very similar in appearance to M10. I swung the telescope back and forth, examining them at 49x, and eventually decided that M12 was a hint sparser, with more bright members resolved in front of the background glow.

An hour earlier, his notes read: "An easy, lumpy glow at 49x. At 122x, a sprinkling of brighter members were resolved, with a medium-bright glow behind it."

Steve Coe

Coe, using a 13" f/5.6, notes: "(M 12) is a very nice globular, it fills the field at 175X and is resolved at all powers with the 18". It is bright, large, elongated and somewhat compressed. There are many lovely streamers of stars winding their way out from a very bright core. I estimated 80 stars resolved by counting 20 members in the SE quadrant of this compact globular. This cluster has a pearly luminescence that is rare in star clusters. 13" Sentinel--150X, very bright, large, irregularly round, much brighter middle, rich, much compressed, 98 * resolved by count, nice chains of stars straggle out from core."

Contemporary observations

Auke Slotegraaf

1982

In a 15.5-inch reflector, this globular, like M10, shows a large number of bright field stars within a 23' field of view. There are about a dozen bright (9-10th magnitude) stars in the field, and a similar red star lies immediately south of the cluster's nucleus. The nucleus is mottled, and comprises more than three-quarters of the whole cluster. As a whole, the globular looks fluffy, partially because a nucleus is not readily discernible, and partially because of the small star streamers emanating from the central area. The majority of these streamers lie to the north of the nucleus.

1995 June 01

1995-06-01: 11x80. Kelsey Farm. 22:00 SAST. A bright globular in a busy field, large and small stars. Cluster appears mostly nucleus with only a small fringe.

1997 July 08

1997 July 8, Tuesday, 20:55 - 23:30 Jonkershoek. 11x80's tripod-mounted. Glorious cluster, large, surrounded by many 9-10th mag stars. Dominates the 4 degree field of view. Soft milky glow, broad centre. Unsure - could be trick of the eye, but appears elongated SE - NW?

Magda Streicher

(no date)

12-inch f/10 SCT (EP: 2-inch 40mm SW 76x 53' fov; 2-inch 32mm SW 95x 42' fov; 2-inch 14mm UW 218x 23' fov)

Beautiful bright globular that is well resolved with different magnitude stars (76x). Clear star strings danced out from the dense core (95x), with two outstanding short strings on the eastern side. The star strings as a whole in this globular are very unique and special. The core is very dense when compared to other globular's in Ophiuchus. There is haziness towards the southwest with a few faint stars, which can explain the somewhat oval appearance (218x). Just outside the eastern edge a few bright stars arranged in a square. The globular is situated to the north west of M10. Discovered on May 30, 1764 by Charles Messier. (Mag 6.1; size 16.0'; brightest stars 12.0 mag. )

Carol Botha

2007 April 15

2007 April 15, 01:00 UT

Sutherland

8-inch f5 Dobsonian (EP: 15mm 45' fov)

Conditions: Clear

Globular cluster(M12) in Ophiuchus. Finding it more difficult to locate than its neighbour M10. The object seems of even density without a brighter nucleus but with averted vision the cluster appears slightly brighter towards the middle. It appears slightly elongated north-south . When looking directly it looks like a spun cocoon or almost like a thumbprint. I cannot resolve any stars. In the same field are a number of bright stars .One star nestles at the southern edge of the cluster with another star to south-east. Three stars form a straight line from ESE to NNW with two stars west of the cluster.

Richard Ford

2016, June, 4th

Location:Perdeberg.

Time:9:15pm.

Sky Conditions:The fainter parts of the Milky Way are barely visible.Haziness only visible on the horizon.Atmosphere stable with little interference.

Instrument:12-inch Dobsonian.

M12 is a loosely concentrated globular cluster that is large which is well resolved into 6th to 7th magnitude stars.This globular cluster looks like an irregular slightly diffuse snowball.This globular cluster measures 11.2'x 8'.Chart No:292,NSOG Vol.2.

2009 August 15th Saturday

Location:Perdeberg.

Instrument:12"Dobsonian Reflector Telescope.

Sky Conditions:The fainter parts of the Milky Way are barely visible.

Transparency of the Sky:Haziness only visible on the horizon.

Seeing:Atmosphere stable with little interference.

Limiting Magnitude:4.9.

First Impression:Globular Cluster.

Location:Ophiuchus.

Time:8:07pm.

Chart Number:No.12(Extract taken out of "Atlas of the Night Sky").

Brightness:Very Bright.

Brightness Profile:High Surface Brightness.

Challenge Rating:Stunning in a large telescope under a dark sky.

Overall Shape:Slightly oval,this globular cluster is slightly off center with an irregularity of bright stars clearly resolved in this cluster.

Are individual stars seen? This globular cluster is well resolved into hundreds of thousands of bright stars.

How are the stars concentrated towards the nucleus? The bright individual stars in this globular cluster is slightly concentrated towards the center.

Estimate the size of the nucleus vs.halo: Nucleus(14.5') Halo(13').

Are there clumps/chains of stars? Yes.

Prominent empty spaces/starless patches? Yes,on the outskirts of this globular cluster.

Tom Bryant

2008-07-03 00:00:00

Observing site: Pinnacles overlook

Telescope: C-8

[16h 47m 12s, -1 57' 0"] A large, loose cluster. Approximately 75 stars were seen with direct vision.

2008-04-02 02:00:00

Observing site: Little Tycho Observatory

Telescope: C-8

[16h 47m 12s, -1 57' 0"] As large as M5, but more sparse. This cluster needs rural skies to be seen to full advantage.

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