Messier 54

Discovered on July 24, 1778 by Charles Messier.

Messier: M54.

July 24, 1778. 54. 18h 40m 52s (280d 12' 55") -30d 44' 01"
"Very faint nebula, discovered in Sagittarius; its center is brilliant & it contains no star, seen with an achromatic telescope of 3.5 feet [FL]. Its position has been determined from Zeta Sagittarii, of 3rd magnitude."

William Herschel

[Unpublished Observations of Messier's Nebulae and Clusters. Scientific Papers, Vol. 2, p. 657]
1784, June 24 (Sw. 232). A round, resolvable nebula. Very bright in the middle and the brightness diminishing gradually, about 2 1/2' or 3' in diameter. 240 shews too pretty large [bright] stars in the faint part of the nebulosity, but I rather suppose them to have no connection with the nebula. I believe it to be no other than a miniature cluster of very compressed stars resembling that near the 42nd Comae [M53 - Dreyer]. It is like that under [south of] Delta Sagittarii [H I.50 = NGC 6624 - Dreyer], but rather larger and brighter tho' not much.
1784, July 13 (Sw. 237). A cL. vB. R. nebula, mbM. [A considerably large, very bright, round nebula, much brighter to the middle] and breaking off suddenly, the rest being much fainter.

Dunlop: Dun 624.

No. 624. A.R. 18:46: 7, S.P.D. 59:18 (1827) [Right Ascension and South Polar Distance]
"A very beautiful nebula, with a very bright round well-defined disk or nuclei [sic!], about 15" diameter, surrounded by a gradually decreasing light or chevelure, about 1 1/4' diameter; this is exceedingly bright immediately at the centre." 4 Observations.

John Herschel (1847): h 3763.

h 3763 = M. 54 = Dun. 624.
Sweep 476 (July 31, 1834).
RA 18h 44m 10.7s, NPD 120d 41m 5s (1830.0) [Right Ascension and North Polar Distance]
Glob. Cl.; B; R; g m b M; diam in RA = 9s; clearly resolved with left eye.
Globular Cluster; bright; round; gradually much brighter toward the middle; diameter in RA = 9s [2.25']; clearly resolved with left eye.

Sweep 477 (August 1, 1834).
RA 18h 44m 10.7s, NPD 120d 39m 39s (1830.0)
Glob. Cl.; B; p L; v l E; g b M; 2 1/2' diam; resolved into st 15 m, with a few outliers 14 m.
Globular Cluster; bright; pretty large; very little elongated; gradually brighter toward the middle; 2 1/2' diameter; resolved into stars of 15 m, with a few outliers of 14 m.

Sweep 619 (August 15, 1835).
RA 18h 44m 11.1s, NPD 120d 40m 54s (1830.0)
v v B; R; p s v m b M, to a large nipple; diam 2 1/2'; pos of a * 13m, almost involved = 147deg +/-
very very bright; round; pretty suddenly very much brighter toward the middle, to a large nipple; diameter 2 1/2'; position of a star of 13m, almost involved, at position angle 147deg +/-.

RA 18h 44m ..., NPD 120d 39m 30s (1830.0)
Obs in equatorial zone rev, July 16, 1836, on a neb. B, s b M; 90".
Observed in equatorial zone review, July 16, 1836, on a nebula. Bright, suddenly brighter toward the middle; 90" [diameter].

John Herschel, General Catalogue: GC 4442.

GC 4442 = h 3763 = M54 = Dunlop 624.
RA 18h 46m 6.2s, NPD 120d 38' 29.7" (1860.0). [Right Ascension and North Polar Distance]
Glob. Cl.; vB; L; R; g,smbM; rrr; st 15. 6 observations by W. & J. Herschel.
Globular cluster; very bright; large; round; gradually, then suddenly much brighter toward the middle; well resolved; stars of 15th magnitude.

Dreyer: NGC 6715.

NGC 6715 = GC 4442 = h 3763; M 54, Dunlop 624.
RA 18h 46m 6s, NPD 120d 38.5' (1860.0). [Right Ascension and North Polar Distance]
Glob. Cl., vB, L, R, g, smbM, rrr, st 15; = M54
Globular cluster, very bright, large, round, gradually, then suddenly much brighter toward the middle, well resolved, stars of 15th magnitude.

Curtis

[Descriptions of 762 Nebulae ans Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 6715, RA=18:48.7, Dec=-30:36. M54. Remarkably condensed globular cluster 2' in diameter. 0 s.n.