Messier 55

Discovered on June 16, 1752 by Nicholas Louis de Lacaille.

Messier: M55.

July 24, 1778. 55. 19h 26m 02s (291d 30' 25") -31d 26' 27"
"A nebula which is a whitish spot, of about 6' extension, its light is even and does not appear to contain any star. Its position has been determined from zeta Sagittarii, with the use of an intermediate star of 7th magnitude. This nebula has been discovered by M. l'Abbe de LaCaille, see Mem. Acad. 1755, p. 194 [Glyn Jones has erroneously 1775]. M. Messier has looked for it in vain on July 29, 1764, as reported in his memoir."

Lacaille: Lac I.14.

19:24:20, -31:29:00
It resembles an obscure nucleus of a big comet.
[1763] Observed on June 16, 1752.

Bode: Bode 63.

"Like a dark cometary nucleus."

Dunlop: Dun 620.

No. 620. A.R. 19:30:54, S.P.D. 58:35 (1827) [Right Ascension and South Polar Distance]
"A beautiful large round bright nebula, about 2' diameter, slight condensation to the centre." 2 Observations.

Caroline Herschel

July 30. 1783. Observed M55, M2, M16 and M25.

William Herschel

[PT 1818 p. 444, SP2 p. 599]
The 55th of the Connoissance. [M 55 = NGC 6809]
"1783, small 20 feet telescope. With 250 fairly resolved into stars; I can count a great many of them, while others are too close to be distinguished separately."
"1784, 1785, 20 feet telescope. A rich cluster of very compressed stars, irregularly round, about 8 minutes long."
By the obserevation of the small 20 feet telescope, which could reach stars 38.99 times as far as the eye, the profundity of this cluster cannot be much less than of the 467th order: I have taken it to be of the 400th order.

John Herschel (1847): h 3798.

h 3798 = M. 55 = Dun. 620.
Sweep 478 (August 3, 1834).
RA 19h 29m 12.3s, NPD 121d 21m 6s (1830.0) [Right Ascension and North Polar Distance]
Glob. Cl.; p B; v L; R; v g l b M; diam in RA 30.0s; all resolved into separate st 13...16 m; not so comp M as to run together into a blaze or nipple.
Globular Cluster; pretty bright; very large; round; very gradually little brighter toward the middle; diameter in RA 30.0s [7.5']; all resolved into separate stars of 13 to 16 m; not so compressed toward the middle as to run together into a blaze or nipple.

Sweep 618 (August 14, 1835).
RA 19h 29m 14.5s, NPD 121d 18m 15s (1830.0)
Glob. Cl.; a fine L, R, cluster; 6' diam; all clearly resolved into st 11, 12, 13m; does not come up to a nipple.
Globular Cluster; a fine large, round cluster; 6' diameter; all clearly resolved into stars of 11, 12, and 13m; does not come up to a nipple.

John Herschel, General Catalogue: GC 4503.

GC 4503 = h 3798 = M55 = Dunlop 620.
RA 19h 31m 7.9s, NPD 121d 15' 44.2" (1860.0). [Right Ascension and North Polar Distance]
Glob. Cl.; pB; L; R; vRi; vgbM; st 12...15. 5 observations by W. & J. Herschel.
Globular cluster; pretty bright; large; round; very rich; very gradually brighter toward the middle; stars from 12th to 15th magnitude.

Dreyer: NGC 6809.

NGC 6809 = GC 4503 = h 3798; Lac I.14, M 55, Dunlop 620.
RA 19h 31m 8s, NPD 121d 15.7' (1860.0). [Right Ascension and North Polar Distance]
Glob. Cl., pB, L, R, vRi, vgbM, st 12...15; = M55
Globular cluster, pretty bright, large, round, very rich, very gradually brighter toward the middle, stars from 12th to 15th magnitude.

Curtis

[Descriptions of 762 Nebulae and Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 6809, RA=19:33.7, Dec=-31:10. M. 55. A fine globular cluster 10' in diameter. The background of faint stars is less dense near the center than in most clusters of this type. 4 s.n.