Messier 12

Discovered by Charles Messier on May 30, 1764.

Messier: M12.

May 30, 1764. 12. 16h 34m 53s (248d 43' 10") -2d 30' 28"
Nebula discovered in the Serpent, between the arm and the left side of Ophiuchus: this nebula contains no star, it is round & its light is faint; near this nebula there is a star of 9th magnitude. M. Messier reported it on the 2nd chart of the comet observed in 1769. Mem. Acad. 1775, pl. IX. Seen again March 6, 1781. (diam. 3')

[Handwritten remark in Messier's copy:] Seen again March 10, 1790.

[Mem. Acad. for 1771, p. 439-440 (first Messier catalog)]
In the same night of [May] 30 to 31, 1764, I have discovered a nebula in Serpens, between the arm & left side of Ophiuchus, according to the charts of Flamsteed: That nebula doesn't contain any star; it is round, its diameter can be 3 minutes of arc, its light is faint; on sees it very well with an ordinary [non-achromatic] refractor of 3 feet [FL]. I have determined its position, by comparing with the star Delta Ophiuchi; its right ascension has been concluded at 248d 42' 10", & its declination at 1d 30' 28" south. I have marked it in the chart of the apparent path of the Comet which I have observed last year [the comet of 1769].
[p. 455] 1764.May.30. RA: 248.43.10, Dec: 1.30.28.A, Diam: 0. 3. Nebula without stars, in the Serpent, between the arm and the left side of Ophiuchus.

Bode: Bode 32.

2 nebulae without stars close together [with M10]
On August 14 [1774], I discovered in Ophiuchus two new nebulae not far from each other. One of them is situated south of 14, 16, 19 and 21 Oph near the western arm, the other below this one and eastward, closely west of 30 Oph. These nebulae appear very pale, and because of this, I found not very reliably the separation to Lambda as 6deg 7', to the star 14 as 3deg 50', and to 21 as 3deg 32'. The other one is separated from the 21st star by 5deg 32', and by 1deg 4' from the 30th, as shown in the second figure.

Koehler: Koehler No. 5

[Nebula] Just in the same place [as M10], longitude 7deg [Sgr] [247d]; latitude 20deg north.

Caroline Herschel

May 22, 1783. Observed M12, M5 (which she first took for a comet), M10, and M11.

William Herschel

[PT 1818 p. 438-439, reprinted in Scientific Papers, Vol. 2, p. 596]
The 12th of the Connoissance. [M 12 = NGC 6218]
"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 with all open, the lowest power shows the stars."
"1785, 1786, 20 feet telescope. A brilliant cluster, 7 or 8 minutes in diameter; the most compressed parts about 2 minutes."
With an aperture of 5 inches the 10 feet telescope had a gauging power of 15.53; and this cluster is consequently of a profundity of the 186th order.

John Herschel (1833): h 1971.

h 1971 = M12.
Sweep 146 (April 15, 1828)
RA 16h 38m 24.8s, NPD 91d 38' 22" (1830.0) [Right Ascension and North Polar Distance]
v rich globular cluster. The stars 10 ... 16m; v g m b M, but has stragglers in lines and branches extending some distance from the most condensed part, which is 3' diam. Comes almost up to a blaze in the middle, has a * 10.11 m in the centre.
Very rich globular cluster. The stars are of 10th to 16th magnitude; very gradually much brighter toward the middle, but has stragglers in lines and branches extending some distance from the most condensed part, which is 3' in diameter. Comes almost up to a blaze in the middle, has a star of 10th or 11th magnitude in the centre.

Sweep 5 (May 21, 1825)
RA 16h 38m 24.8s, NPD 91d 38' 25" (1830.0)
Irreg. R; vL; 10' diam with stars from 10 .. 20m
Irregularly round; very large; 10' diameter with stars from 10th to 20th magnitude.

Viewed June 1, 1833. Very like M. 10, but the stars more separated and fewer. It is also rather larger. A fine object. Stars 10.11....15m.
Viewed June 1, 1833. Very like M. 10, but the stars more separated and fewer. It is also rather larger. A fine object. Stars of 10th or 11th to 15th magnitude.

Smyth: DXC [590]. M12.

DXC. 12 M. Ophiuchi.
AR 16h 38m 56s, Dec S 1d 40'.3
Mean Epoch of Observation: 1837.61 [Aug 1837]
A fine rich globular cluster, between the right hip and the elbow of Ophiuchus, with a cortège of bright stars, and many minute straggling outliers. This resolvable mass is greatly condensed towards the centre, with several very bright spots; it was discovered by Messier in 1764, but, probably from the imperfection of his means, was registered as "a round nebula, unaccompanied by any star." Its place was obtained by differentiating with Epsilon Ophiuchi, from which it is 8deg 1/2 distant, on a north-west-by-west line, leading nearly upon Beta.
Sir William Herschel resolved this object in 1783; and in the folowing year his 20-foot reflector made it "a brilliant cluster, 7' or 8' in diameter; the most compressed parts about 2'." By the gauging process, he held its profundity to be of the 186th order.

Lord Rosse

John Herschel, General Catalogue: GC 4238.

GC 4238 = h 1971 = M12.
RA 16h 39m 58.1s, NPD 91d 41m 47.4s (1860.0) [Right Ascension and North Polar Distance]
!!; Glob. Cl.; vB; vL; iR; gmbM; rrr; st 10... 7 observations by W. & J. Herschel.
Very remarkable; globular cluster; very bright; very large; irregularly round; gradually much brighter toward the middle; well resolved; stars of 10th magnitude and fainter.

Huggins

[Further Observations on the Spectra of some Nebulae, with a Mode of determining the Brightness of these Bodies. Phil. Trans. Roy. Soc., Vol. 156 (1866), p. 381-397; here p. 389]
[No. [GC] 4238. 1971 h. 12 M. R.A. 16h 39m 58s.1. N.P.D. 91d 41' 47".4. Cluster; very bright.]
"Hairy branches with slightly spiral arrangement." - Lord Oxmantown [Rosse]
Spectrum continuous.

Dreyer: NGC 6218.

NGC 6218 = GC 4238 = h 1971; M 12.
RA 16h 39m 58s, NPD 91d 41.7m (1860.0) [Right Ascension and North Polar Distance]
!! Glob. Cl., vB, vL, iR, gmbM, rrr, st 10...; = M12
Very remarkable globular cluster, very bright, very large, irregularly round, gradually much brighter toward the middle, well resolved, stars of 10th magnitude and fainter.

Curtis

[Descriptions of 762 Nebulae ans Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 6218, RA=16:42.0, Dec=- 1:46. [Publ. Lick Obs.] Vol. VIII, Plate 54. Fine globular cluster; central part about 2'; outer about 8' in diameter. Apparently somewhat less compact than most globular clusters. 0 s.n.