Messier 4

Discovered by Philippe Loys de Chéseaux in 1746.
Independently rediscovered by Nicholas Louis de Lacaille in on April 13, 1752.

Messier: M4.

May 8, 1764. 4. 16h 09m 08s (242d 16' 56") -25d 55' 40"
Cluster of very small [faint] stars; with an inferior telescope, it appears more like a nebula; this cluster is situated near Antares & on its parallel. Observed by M. de la Caille & reported in his catalog. Seen again January 30 & March 22, 1781. (Diam 2.5')

[Mem. Acad. for 1771, p. 437 (first Messier catalog)]
On May 8, 1764, I have discovered a nabula near Antares, & on its parallel, it is a light which has little extension, which is faint, & which is difficult to be seen: when employing a good telescope for viewing it, one can perceive very small stars. Its right ascension has been determined at 242d 16' 56", & its declination as 25d 55' 40" south.
[p. 454] 1764.May.8. RA: 242.16.56, Dec: 25.55.40.A, Diam: 0. 2 1/2. Cluster of very small stars, near Antares and below its parallel.

De Chéseaux: De Ch. No. 19.

One which is near Antares, which I have found, for this year, at RA 242d 1' 45" and declination 25d 23' 30". It is white, round and smaller than the previous ones; I don't know anyone who noted it previously.

Lacaille: Lac. I.9.

16:08:33, -25:54:55.
It resembles a small nucleus of a faint comet.
[1763] Observed on April 13, 1752.

Bode: Bode 31.

A nebula like the nucleus of a comet.

Caroline Herschel

May 5, 1783. Observed M4, M9, and M23.

William Herschel

[PT 1814 p. 248-284, here p. 270, reprinted in Scientific Papers, Vol. 2, p. 533]
Connoiss. 4 is "A rich cluster of considerably compressed small stars surrounded by many straggling ones. It contains a ridge of stars running through the middle from south preceding [SW] to north following [NE]. The ridge contains 8 or 10 pretty bright stars. All the stars are red."
The curious construction of this cluster is sufficiently accounted for by the bright stars in what is called a ridge; the small stars accumulated about it having somewhat the appearance of the shelving sides of the ridge. The observed red colour was probably owing to the low situation of the object.

[PT 1818, p. 429-470, here p. 436-437, reprinted in Scientific Papers, Vol. 2, p. 595]
The 4th of the Connoissance.
"1783, 10 feet telescope. All resolved into stars. I can count a great number of them, while others escape the eye by their minuteness."
"1783, small 20 feet telescope. All resolved into stars."
"1784, 20 feet telescope. The cluster contains a ridge of stars in the middle, running from south preceding [SW] to north following [NE]."
The 10 feet telescope having a power to show stars exceeding that of the eye 28.67 times, gives the profundity of this cluster of the 344th order.

Smyth: DLXIX [569]. M4.

DLXIX. 4 M. Scorpii.
AR 16h 13m 51s, Dec S 26d 07'.5
Mean Epoch of Observation: 1837.36 [Apr 1837]
A compressed mass of very small stars, in the middle of the creature's body, with outliers and a few small stellar companions in the field. The place is carefully differentiated with Antares; from which it is only 1deg 1/2 distant to the west. This object is elongated vertically, and has the aspect of a large, pale, granulated nebula, running up to a blaze in the centre. It was discovered by Messier in the year 1764, and duly reported in the Connoissance des Temps. In 1783, Sir William Herschel resolved this object into stars; and gauging it by a modification of the method which he applied to fathom the Galaxy, he concluded that his 10-foot reflector, having the power to show stars exceeding that of the eye 28.67 times, gave the profundity of this cluster of the 344th order. He describes it as having a ridge of eight or ten pretty bright stars, running from the middle to the nf [north following, NE]; a description which I found very correct.
Under the head of 80 Messier (which see, No. DLXIV [564]), a slight allusion was made to nebulae considered in their relations to the surrounding spaces. Like that singular mass, the group before us is also situated on the western edge of an area which contains no stars, i.e., none of which we can decry; and in such spaces invariably, according to the testimony of Sir William Herschel, are nebulae found. "Let us," says M. Arago, "connect these facts with the observation which has shown that the stars are greatly condensed towards the centre of spherical nebulae, and with that which has afforded the proof that these stars sensibly obey a certain power of condensation (or clustering power), and we shall feel disposed to admit with Herschel, that nebulae are sometimes formed by the incessant operation of a great number of ages, at the expense of the scattered stars (étoiles dispersées) which originally occupied the surrounding regions; and the existence of empty, or ravaged spaces, to use the picturesque expression of the great astronomer, will no longer present anything which ought to confound our imagination."

John Herschel, General Catalogue: GC 4183.

GC 4183 = M4 = BAC 5455.
RA 16h 15m 3.6s, NPD 116d 11m 11.1s (1860.0) [Right Ascension and North Polar Distance]
Cl; 8 or 10 L st in line, with 5 st; rrr. 4 observations by W. & J. Herschel.
Cluster; 8 or 10 bright stars in a line, with 5 stars; well resolved.

Dreyer: NGC 6121.

NGC 6121 = GC 4183; Lac I.9, M 4.
RA 16h 15m 4s, NPD 116d 11.2m (1860.0) [Right Ascension and North Polar Distance]
Cl, 8 or 10 B st line, with 5 st, rrr; = M4
Cluster, 8 or 10 bright stars in a line, with 5 stars, well resolved.