Messier 15

Discovered by Jean-Dominique Maraldi on September 7, 1746.

Messier: M15.

June 3, 1764. 15. 21h 18m 41s (319d 40' 19") +10d 40' 03"
Nebula without a star, between the head of Pegasus and that of Equuleus; it is round, in the center it is brilliant, its position was determined by comparison with Delta Equulei. M. Maraldi, in the Memoirs of the Academy of 1746, reports of this nebula: "I have found, he says, between the stars Epsilon Pegasi and Beta Equulei, a fairly bright nebulous star, which is composed of many stars; its right ascension is 319d 27' 6", and its northern declination is 11d 2' 22". (diam. 3')

[Mem. Acad. for 1771, p. 442 (first Messier catalog)]
In the night of June 3 to 4, 1764, I have discovered a nebula between the head of Pegasus & that of Equuleus it is round, its diameter is about 3 minutes of arc, the center is brilliant, I have not dustinguished any star; having examined it with a Gregorian telescope which magnifies 104 times, it had little elevated over the horizon, & maybe that observed at a greater elevation one can perceive stars: I have compared it with the star Delta Equulei; its right ascension has been concluded at 319d 40' 19", & its declination at 10d 40' 3" north. I have also marked that nebula in the chart of the apparent path of the Comet of 1764.
In the Memoirs of the Academy for 1746, M. Maraldi speaks of that nebula. "I have perceived, he says, between the stars Epsilon Pegasi & Beta Equulei, a rather bright nebulous star which is composed of many stars, of which I have determined the right ascension of 319d 27' 6", & its northern declination of 11d 2' 22"."
[p. 455] 1764.Jun.3. RA: 319.40.19, Dec: 10.40. 3.B, Diam: 0. 3. Nebula without stars, between the heads of Pegasus and Equuleus.

Maraldi:

[September 7, 1746] On September 7 I noticed between the stars Epsilon Pegasi & Beta Equulei, a fairly bright nebulous star, which is composed of many stars, of which I have determined the right ascension of 319d 27' 6", & its northern declination of 11d 2' 22".

Bode: Bode 71.

A small nebula.
On September 23 [1774], I found a new nebulous star with the 7-foot telescope, northward between the stars Epsilon or Enif, at the mouth of Pegasus, and Delta and Gamma at the mouth og Equuleus. It shows up as well as of round shape and enveloped in a dense nebula, wherein no stars are recognizable. I determined its separation from Epsilon as 4deg 14' and from Delta as 4deg 28'. It has about three small stars which are not contained in Flamsteed's catalog, a position as shown in the fourth figure, the separation of which I have mutually determined with the heliometer.

Koehler: Koehler No. 15

[Nebula] Between A in Pegasus and D in Equuleus.

William Herschel

[PT 1814 p. 276, reprinted in Scientific Papers, Vol. 2, p. 536]
Nov. 23, 1805. Large 10 feet. "The 15th of the Connoiss. [M 15 = NGC 7078] is perfectly round, and insulated. The accumulation of stars towards the centre is more sudden that the 13th of the Connoiss. [M 13] and the scattered stars extend proportionally much farther. Its diameter is 1/6 of the field of the glass which magnifies 108 times, that is to say 4'0". It passes the wire in 13".0 of time which by calculation gives only 2'11".3, but I rely more on the estimation by the known field of view which is 24'0"; because the limits of the cluster cannot be properly fixed upon transit."

[PT 1818 p. 440-441, reprinted in Scientific Papers, Vol. 2, p. 597]
The 15th of the Connoissance. [M 15 = NGC 7078]
"1799. It is visible to the eye."
"1783, 1794, 7 feet telescope. With 278 the stars of the cluster may be seen."
"1799, 10 feet telescope. With an aperture of 4 inches, no trace of stars is visible. 1817, with an aperture of 4.56 inches, which gives a gaging power of 14, it appears like a nebulous patch, gradually brighter in the middle; with a gaging power of 16, the hazy border is larger; with 18, the whole of it much larger and brighter; with 20, resolvable; and with 22, the stars are visible."
"1784, 1787, 1807, 20 feet telescope. A globular cluster of stars, about 6 minutes in diameter."
"1810, large 10 feet telescope. The diameter, with 171, is full 4'30", and taking in the stars that probably belong to it, it is 6'45"."
By the observation of the 7 feet telescope, the profundity of this cluster is of the 243d order.

John Herschel (1833): h 2120.

h 2120 = M15.
Sweep 14 (October 13, 1825)
RA 21h 21m 43.0s, NPD 78d 34' 19" (1830.0) [Right Ascension and North Polar Distance]
vB; vL; irreg. R; g b and v s m b M. A magnificent globular cluster; comes up to a perfect blaze in the centre, like a protuberance or nipple; not the condensation of a homogeneous globe; it has straggling streams of stars, as it were, drawing to a centre. It is not round. Has a * 8 m, 30s following in parallel.
very bright; very large; irregularly round; gradually brightening and very suddenly much brighter toward the middle. A magnificent globular cluster; comes up to a perfect blaze in the centre, like a protuberance or nipple; not the condensation of a homogeneous globe; it has straggling streams of stars, as it were, drawing to a centre. It is not round. Has a star of 8th magnitude, 30 sec following [East] in parallel.

Sweep 13 (October 12, 1825)
RA 21h 21m 43.0s, NPD 78d 36' +/- (1830.0)
Superb; very comp; irreg R; vS stars 15m, all distinct but running together into a blaze in middle; 4' or 5' diam. One * 8m n f dist 10'.
Superb; very compressed; irregularly round; very small [faint] stars of 15th magnitude, all distinct but running together into a blaze in the middle; 4' or 5' diameter. One star of 8th magnitude is north following [NE] at a distance of 10'.

Smyth: DCCLXXXV [785]. M15.

DCCLXXXV. 15 M. Pegasi.
AR 21h 22m 13s, Dec N 11d 27'.4
Mean Epoch of Observation: 1836.72 [Sep 1836]
[with a drawing]
A globular cluster between the mouths of Pegasus and Equuleus, forming the northern vertex of a triangle, obtuse and nearly isosceles, of which the base is Beta Pegasi and Delta Equulei. This fine object was discovered by Maraldi in 1745, and registered as "une étoile nébuleuse, assez claire, qui est composée de plusieurs étoiles." Messier could not quite make this out, but in 1764 described it as a nebula with [actually without] a star, its form circular and centre brilliant; and the place he assigned to it is very considerably in error [actually about 20']. Thus it remained till 1783, when Sir William Herschel resolved it into stars, and found it a good object for proving the telescope's space-penetrating power; he estimated its profundity to be of the 243rd order.
Although this noble cluster is rated as globular, it is not exactly round, and under the best circumstances is seen as in the diagram, with strgglers branching from a central blaze. Under a moderate magnifying power, there are many telescopic and several brightish stars in the field; but the accumulated mass is completely insulated, and foreibly strikes the senses as being almost infinitely beyond those apparent comites. Indeed, it may be said to appear evidently aggregated by mutual laws, and part of some stupendous and inscrutable scheme of involution; for there is nothing quiescent throughout the immensity of the vast creation.

John Herschel, General Catalogue: GC 4670.

GC 4670 = h 2120 = M15 = Lalande 40815.
RA 21h 23m 9.9s, NPD 78d 27' 22.3" (1860.0) [Right Ascension and North Polar Distance]
!; Glob. Cl.; vB; vL; iR; vsmbM; rrr; st vS. 16 observations by W. & J. Herschel.
Remarkable; globular cluster; very bright; very large; irregularly round; very suddenly much brighter toward the middle; mottled; stars very small [faint].

Huggins

[Phil. Trans. Roy. Soc., Vol. 155 (1865), p. 39-42; here p. 40]
"[GC] 4670, 2120 h. 15 M. Very bright cluster; well resolved."
This cluster gave a continuous spectrum.

Dreyer: NGC 7078.

NGC 7078 = GC 4670 = h 2120; Maraldi, M 15 = Lalande 40815.
RA 21h 23m 13s, NPD 78d 26.7' (1860.0) [Right Ascension and North Polar Distance]
!, Glob. Cl., vB, vL, iR, vsmbM, rrr, st vS; = M15
Remarkable, globular cluster, very bright, very large, irregularly round, very suddenly much brighter toward the middle, well resolved, very small [faint] stars.

Curtis

[Descriptions of 762 Nebulae ans Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 7078, RA=21:25.2, Dec=+11:43. A bright, unusually beautiful globular cluster 8' in diameter. 17 s.n.