Messier 6

Discovered by Hodierna before 1654.
Independently rediscovered by De Chéseaux 1745-46.
Independently rediscovered by Lacaille on June 16, 1752.

Messier: M6.

May 23, 1764. 6. 17h 24m 42s (261d 10' 39") -32d 10' 34"
A cluster of small stars between the bow of Sagittarius & the tail of Scorpius. To the naked eye, this cluster seems to form a nebula without stars; but even with the smallest instrument one employs for investigating one sees a cluster of small [faint] stars. (Diam. 15')

[Handwritten remark:] Lacaille has it.

[Mem. Acad. for 1771, p. 438 (first Messier catalog)]
In the same night of May 23 to 24, 1764, I have determined the position of a cluster of small stars between the bow of Sagittarius & the tail of Scorpius: At simple view [with the naked eye], this cluster appears to form a nebula without stars, but the slightest instrument which one employs to examine it mahes one see that it is nothing but a cluster of small stars, the diameter of which could be 15 arc minutes: I have determined its position during its passage of the Meridian : ist right ascension was 261d 10' 39", & its declination 32d 10' 34" southern.
[p. 455] 1764.May.23. RA: 261.10.39, Dec: 32.10.34.A, Diam: 0.15. Cluster of small stars between the bow of Sagittarius & the tail of Scorpius.

Hodierna: Ha II.4.

De Chéseaux: De Ch. No. 1.

"Between Scorpius, Ophiuchus, and Sagittarius, there is a very beautiful one [cluster], of which the principal stars have this year RA 260d 52' 30" and southern declination 32d 1' 30"."

Lacaille: Lac III.12.

17:24:00, -32:02:45
"Peculiar cluster of small stars,disposed in three parallel bands, forming a lozenge of 20 to 25 diameter and hitched with nebulosity."
[1763] Observed on June 16, 1752.

Bode: Bode 39.

"A cluster of small stars."

William Herschel

[PT 1814 p. 266, reprinted in Scientific Papers, Vol. 2, p. 530]
Connois. 6 is "A cluster of stars of various sizes containing several lines that seem to be drawing to a centre like a forming cluster."

[Unpublished Observations of Messier's Nebulae and Clusters. Scientific Papers, Vol. 2, p. 651]
1783, July 30. 20 feet, lowest power. I counted about 50 stars; it contains the greatest variety of magnitudes of any nebula I recollect. The compound eye-piece shows more of them varuiously and intermixed.
1786, Apr. 30 (Sw. 559). Contains several lines that seem to be drawing to a center like a forming cluster.

Dunlop: Dun 612.

No. 612. A.R. 17:30:--, S.P.D. 57:47 (1827) [Right Ascension and South Polar Distance]
"A cluster of small stars of mixt magnitudes, about 15' diameter, irregular figure." 2 Observations.
[John Herschel identified this object with his h3702 = GC 4323 = NGC 6416, a much less conspicuous, nearby open cluster. Dunlop's position is much closer to that of more prominent M6; therefore, Glen Cozens has proposed this identification, which we adopt here.]

John Herschel (1847): h 3699.

h 3699 = M. 6.
Sweep 478 (August 3, 1834).
RA 17h 28m 58.6s, NPD 122d 5m 52s (1830.0) [Right Ascension and North Polar Distance]
Chief * 7 m of a fine L, discrete cl of st 10....11 m ; one * is 7 m, one 7.8. Fills field; VIII. class.
Chief star of 7th magnitude of a fine, large, discrete cluster of stars of 10th to 11th magnitude; one star is 7 mag, one 7 to 8 mag. Fills field; [William Herschel's] class VIII [Coarsely scattered clusters of stars].

John Herschel, General Catalogue: GC 4318.

GC 4318 = h 3699 = M6.
RA 17h 30m 55.8s, NPD 122d 7m 4.9s (1860.0) [Right Ascension and North Polar Distance]
Cl; L; iR; lC; st 7, 10... 4 observations by W. & J. Herschel.
Cluster; large; irregularly round; little compressed; stars of 7th and of 10th magnitude and fainter.

Dreyer: NGC 6405.

NGC 6405 = GC 4318 = h 3699; Lac III.12, M 6.
RA 17h 30m 56s, NPD 122d 7.1m (1860.0) [Right Ascension and North Polar Distance]
Cl, L, iR, lC, st 7, 10...; = M6
Cluster, large, irregularly round, little compressed, stars of 7th and of 10th magnitude and fainter.