Messier 33

Probably discovered by Hodierna before 1654.
Independently discovered by Charles Messier on August 25, 1764.

Messier: M33.

August 25, 1764. 33. 1h 40m 37s (20d 09' 17") +29d 32' 25"
Nebula discovered between the head of the Northern Fish [of Pisces] & the great Triangle, a bit distant from a star of 6th magnitude: The nebula is of a whitish light of almost even density [of brightness], however a little brighter along two-third of its diameter, & contains no star. One sees it with difficulty with an ordinary telescope of 1-foot [FL]. Its position was determined from Alpha Trianguli. Seen again September 27, 1780. (diam. 15')

[Mem. Acad. for 1771, p. 448 (first Messier catalog)]
In the night of August 25 to 26, 1764, I have discovered a nebula between the head of the northern Fish [of Pisces] & the large Triangle [Triangulum], a bit distant from a star whioch had not been known, of sixth magnitude, of which I have determined the position; the right ascension of that star was 22d 7' 13", & its declination 29d 54' 10" north: near that star, there is another one which is the first of Triangulum, described by the letter b. Flamsteed described it in his catalog, of sixth magnitude; it is less beautiful than that of which I have given the position, & one should set it to the rank of the stars of the eighth class [magnitude]. The nebula is a whitish light of 15 minutes in diameter, of an almost even density, despite a bit more luminous at two third of its diameter; it doesn't contain any star: one sees it with difficulty with an ordinary [non-achromatic] refractor of one foot [FL]. I have compared it to the star Alpha Trianguli, & with that of which I have reported the position. I have found the right ascension of that nebula at 20d 9' 17", & its declination of 29d 32' 25" north.
[p. 457] 1764.Aug.25. RA: 20. 9.17, Dec: 29.32.25.B, Diam: 0.15. Nebula without stars, between the head of the northern Fish [of Pisces] & the great Triangle, it has little distance from a new star of 6th magnitude & the star b Trianguli, according to Flamsteed.

Bode: Bode 5.

A small dim nebula.
On August 18 [1775], I found between Alpha in the large Triangle (Tri) and Mirach at the belt of Andromeda a faintly illuminated nebula in an unordered shape. It is actually situated west and about 2/3 of the distance of the star d from Alpha, at the first, somewhat north of the line through Alpha and d. The 12th figure shows its approximate position relative to small stars, which appeared first in the 7-foot telescope.

Bode (1782):

[From: Vorstellung der Gestirne auf XXXIV Kupfertafeln (Introduction to the Stars on 34 Copper Plates), 1782. Here Plate XXX, p. 38]
Fig. 6. The nebula near d in Triangulum (No. 18) with the nearest stars to it visible in telescopes, after Inspector Köhler in Dresden. According to Mr. Messier, it has a diameter of 15 minutes, the nebula appears somewhat more vivid within 2/3 od its diameter; but there are no individual stars recognizable within it.

William Herschel: H V.17.

H V.17. Sept. 11, 1784.
m. [milky] nebulosity. not less than 1/2 deg. broad, perhaps 3/4 degree long, but not determined.

[PT 1800 p. 78-79. Reprinted in: Scientific Papers, Vol. 2, p. 48]
August 24, 1783. I viewed the nebula north preceding Flamsteed's 1 Trianguli, discovered by Mr. Messier, in 1764 [M 33 = NGC 598].
"7-feet reflector; power 57. There is a suspicion that the nebula consists of exceedingly small stars. With this low power it has a nebulous appearance; and it vanishes when I pus on the higher magnifying powers of 278 and 460."
Oct. 28, 1794. I viewed the same nebula with a 7-feet reflector.
"It is large, but very faint. With 120, it seems to be composed of stars, and I think I see several of them; but it will bear no magnifying power."

[PT 1818, p. 442-443. Reprinted in: Scientific Papers, Vol. 2, p. 598]
The 33rd of the Connoissance. [M 33 = NGC 598]
"1799, 10 feet finder. It is visible as a faint nebula."
"1783, 1794, 7 feet telescope. With 75, it has a nebulous appearance; it will not bear 278 and 460, but with 120 it seems to be composed of stars."
"1799, 1810, 10 feet telescope. The brightest part is resolvable; some of the stars are visible."
"1805, 1810, Large 10 feet telescope. The condensation of the stars is very gradually towards the middle; but with the four powers 71, 108, 171, and 220, some nebulosity remains. The stars of the cluster are the smallest points imaginable. The diameter is nearly 18 minutes."
The profindity of this cluster, by the observation of the 10 inch telescope, must be of the 344th order.

[Unpublished Observations of Messier's Nebulae and Clusters. Scientific Papers, Vol. 2, p. 653]
See above pp. 48 and 598. Two observations are recorded as being of V.17, the outlying parts of the great nebula; they were made September 11 and 12, 1784, and described in vol. i. [SP1] pp. 255-256.

John Herschel (1833): h 131.

h 131 = H V.17 = M33.
Sweep 177 (September 15, 1828)
RA 1h 24m 15.6s, NPD 60d 13m 9s (1830.0) [Right Ascension and North Polar Distance]
Enormously L; v g b M. The nucl taken; has * 12 m, n f the nucl. The diffused neb extends 15' s and as much nearly to n. It has irregularities of light, and even feeble subordinate nuclei and many small stars. Probably V.17 is part of the diff neb of M33.
Enormously large; very gradually brighter toward the middle. The nucleus taken; has a star of 12 m, north following [NE] of the nucleus. The diffused nebula extends 15' south and as much nearly to the north. It has irregularities of light, and even feeble subordinate nuclei and many small stars. Probably H V.17 is part of the diffuse nebula of M33.

Smyth: LVII [57]. M33.

LVII. 33 M. Trianguli.
AR 1h 24m 51s, Dec N 29d 51'.3
Mean Epoch of Observation: 1838.74 [Sep 1838]
A large and distinct, but faint pale white nebula, in the precincts of Triangulum, between it and the Northern Fish [of Pisces]; with a bright star a little np [north preceding, NW], and five others following [eastward] at the same distance, between which and the object, there is an indistinct gleam of mere nebulous matter. It was discovered by Messier in 1764; and to WH [William Herschel] had a mottled aspect under his seven-foot reflector, in 1783; but afterwards applying a larger telescope, he resolved it into stars - "the smallest points imaginable." [Actually an illusion - hf] By a method of turning the space-penetrating power of his instrument into a gradually decreasing series of gauging powers, he considered the profundity of this cluster nmust be of the 344th order: i.e., 344 times the distance of Sirius from the earth. It is No. 131 of H. [John Herschel]'s Catalogue of 1833; and the above place is obtained by differentiating with Alpha Trianguli, from which it is about 4deg, and just north a line run from that star to Delta Andromedae.

Lord Rosse

[Phil. Trans. 1850, p. 499-514, drawing on Plate XXXVI, fig. 5]
Plate XXXVI, fig. 5, H. 131. - This figure represents the central portion of a very large nebula. The nebula itself has not been sufficiently examined, but as yet no other portion appears to have a spiral, or indeed any regular arrangement. The sketch is not very accurate, but represents sufficiently well the character of the central portion.
"September 6, 1849. - A spiral.
"September 16, 1849. - New spiral: Alpha the brighter branch; Gamma faint; Delta short but pretty bright; Beta pretty distinct; Epsilon but suspected; the whole involved in a faint nebula, which probably extends past several knots whioch lie about it in different directions. Faint nebula seems to extend very far following: drawing taken.
"September 10, 1849. - An attempt at a drawing taken: fog.
"October, 1849. - The whole nebula in flocculi."

John Herschel, General Catalogue: GC 352.

GC 352 = h 131 = H V.17 = M 33.
RA 1h 25m 56.3s, NPD 60d 3' 50.1" (1860.0) [Right Ascension and North Polar Distance]
!; eB; eL; R; vRi; vgbMN; rr. 14 observations by William and John Herschel.
Remarkable; extremely bright; extremely large; round; very rich; very gradually brighter toward the middle where there is a nucleus; partly resolved (some stars visible) [actually, these are either foreground stars or clusters/star clouds].
Remark: Figures in P.T. 50 [Lord Rosse 1850], plate xxxvi, fig. 5; P.T. 61 [Lord Rosse 1861], plate xxvi, fig. 10.

Dreyer: NGC 598.

NGC 598 = GC 352 = h 131 = H V.17; M 33.
RA 1h 25m 58s, NPD 60d 3.8' (1860.0) [Right Ascension and North Polar Distance]
! eB, eL, R, vgbMN; = M33
Remarkable, extremely bright, extremely large, round, very gradually brighter toward the middle where there is a nucleus.
Remark: Figures in P.T. 50 [Lord Rosse 1850], plate XXXVI, fig. 5; P.T. 61 [Lord Rosse 1861], plate XXVI, fig. 10.

Lick VIII

[Photographs of Nebulae and Clusters, Made with the Crossley Reflector, by James Edward Keeler, Director of the Lick Observatory, 1898-1900. Publications of the Lick Observatory, Vol. VIII, 1908]
[Plate 3. The Spiral Nebula M33 Trianguli]
[p. 30] NGC 598, RA= 1:28:12, Dec=+30: 8.6 (1900.0), M33
[p. 45] No. 3, NGC 598, 1899 Sep 12, exp. 3h 30m, Enl. 2.1, Top W, M33.

Curtis

[Descriptions of 762 Nebulae ans Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 598, RA= 1:28.2, Dec=+30: 9. [Publ. Lick Obs.] Vol. VIII, Plate 3. A close rival to the Nebula of Andromeda as the most beautiful spiral known. With its faintest extensions it covers an area at least 55'x40'. Messier 33 Trianguli. [NGCs] 588, 592, 595, and 603 are simply brighter portions of [NGC] 598. It is uncertain wheter there is an actual stellar nucleus. A multitude of stellar condensations in the whorls; the spiral which furnushes the best known example of ``resolution'' into stars. 7 s.n.