Messier 80

Discovered by Charles Messier on January 4, 1781.

Messier: M80.

January 4, 1781. 80. 16h 04m 00s (240d 59' 48") -22d 25' 13"
Méchain: (241d 00' 26") -22d 27' 58"
"Nebula without star, in Scorpius, between the stars g. [now Rho Ophiuchi] and Delta, compared to g to determine its position: this nebula is round, the center brilliant, & it resembles the nucleus of a small Comet, surrounded with nebulosity. M. Méchain saw it on January 27, 1781." (diam. 2')

William Herschel:

[PT 1814, p. 275, SP2 p. 536]
May 26, 1786. 20 feet telescope. "The 80th of the Connoiss. [M 80 = NGC 6093] is a beautiful, round cluster of extremely minute and very compressed stars about 3 or 4' in diameter; by the increasing compression of the stars the cluster is very gradually very much brighter in the middle."

[PT 1818, p. 450, SP2 p. 601]
The 80th of the Connoissance. [M 80 = NGC 6093]
"1784, 1786, 20 feet telescope. A globular cluster of extremely minute and very compressed stars of about 3 or 4 minutes in diameter; very gradually much brighter in the middle; towards the circumference the stars are distinctly seen, and are the smallest imaginable."
The profundity of this cluster is probably not much less than the 734th order.

Smyth: DLXIV [564]. M80.

DLXIV. 80 M. Scorpii.
AR 16h 07m 28s, Dec S 22d 35'.4
Mean Epoch of Observation: 1837.36 [Apr 1837]
[with drawing]
A compressed globular cluster of very minute stars, on the right foot of Ophiuchus, which is on Scorpio's back. This fine and bright object was registered by Messier in 1780, who described it as resembling the nucleus of a comet; and indeed, from the blazing centre and attenuated disc, it has a very cometary aspect. There are some small stars both above and below its following parallel, of which three of those in the nf [north following, NE] form a coarse triangle; but the field and the vicinity are otherwise barren. An early star of Ophiuchus, No. 17 P. XVI., slightly precedes this splendid conglomerate, about half a degree to the nordward, and though only of the 8th magnitude, is a convenient index to approach to the out-door gazer. Such particulars are not needed by the man with fixed instruments, but will greatly facilitate the operations of those who are more remarkable for intellectual enery than for means.
The mean apparent place is differentiated from Delta Scorpii, from which it lies east, at 4deg distance; and it is mid-way between Alpha and Beta Scorpii.
This is a very important object when nebulae are considered in their relations to the surrounding spaces, which spaces, Sir William Herschel found, generally contain very few stars: so much so, that whenever it happened, after a short lapse of time, that no star came into the field of his instrument, he was accustomed to his assistant, "Make ready to write, Nebulae are just approaching." Now our present object is located on the western edge of a vast obscure opening, or space of 4deg in breadth, in which no stars are to be seen; and Sir William pronounced 80 Messier, albeit it had been registered as nébuleuse sans étoiles [nebula without stars], to be the richest and most condensed mass of stars which the firmament can offer to the contemplation of astronomers. See also 4 Messier, No. DLXIX [469].

John Herschel (1847): h 3624.

h 3624 [= M80].
Sweep 793 (June 27, 1837)
RA 16h 6m 54.8s, NPD 112d 33m 26s (1830.0) [Right Ascension and North Polar Distance]
Glob. Cl.; v B; R; s v v m b M to a blaze; diam in RA = 10.5s. Stars 15 m, all well seen.
Globular Cluster; very bright; round; suddenly very very much brighter toward the middle to a blaze; diameter in RA = 10.5s [2.6']. Stars 15 m, all well seen.

Sweep 588 (May 24, 1835)
RA 16h 6m 55.0s, NPD 112d 32m 27s (1830.0)
Glob. Cl.; v m comp M; p s v m b M; diam 12.0'; st = 14 m; all resolved. Fine object.
Globular Cluster; very much compressed toward the middle; pretty suddenly very much brighter toward the middle; diameter 12.0'; stars are of 14 m; all resolved. Fine object.

John Herschel, General Catalogue: GC 4173.

GC 4173 = h 3624 = M80.
RA 16h 8m 41.9s, NPD 112d 37' 34.1" (1860.0) [Right Ascension and North Polar Distance]
!!!; Glob. Cl.; vB; L; vmbM (var*); rrr; st 14. 2 observations by W. & J. Herschel.
Magnificient; globular cluster; very bright; large; very much brighter toward the middle (where there is a variable star [probably the nova]); well resolved; stars of 14th magnitude.
Remark: 4173. h 3624 = M. 80. This is Pogson's globular cluster, with a variable star in the centre, for whose most singular history see the Monthly Notes of the R. Ast. Soc. xxi. pp. 32, 33, by Mr. Pogson. Mr. P. in that statement says that Sir J. Herschel (among others mentioned) had described it as either "cometary" or "nebulous." This is incorrect. In both my observations of this object it stands described as a globular cluster, all completely resolved into stars. (See C.G.H. h. 3624).

Dreyer: NGC 6093.

NGC 6093 = GC 4173 = h 3624; M 80.
RA 16h 8m 42s, NPD 112d 37.5' (1860.0) [Right Ascension and North Polar Distance]
!! Glob. Cl., vB, L, vmbM (var*), rrr, st 14; = M80
Very remarkable globular cluster, very bright, large, very much brighter toward the middle (where there is a variable star [probably the nova]), well resolved, stars of 14th magnitude.
Remark: 6093. M 80. In this well-resolved globular cluster Auwers saw a new star of the 7th mag on May 21, 1860 (A.N. 1267 and 2715), which was also found by Pogson on the 28th, and remained visible until about June 10. This phenomenon bears a close resemblance to the "new star" in the Andromeda nebula [M31] in 1885 [SN 1885].

Curtis

[Descriptions of 762 Nebulae and Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 6093, RA=16:11.5, Dec=-22:44. Small, bright globular cluster; the diameter of the brighter part is 3'. 5 s.n.