Messier 100

Discovered by Pierre Méchain on March 15, 1781.

Messier: M100.

April 13, 1781. 100. 12h 11m 57s (182d 59m 19s) +16d 59' 21"
Nebula without star, of the same light as the preceding [M99], situated in the ear of Virgo. Seen by M. Méchain on March 15, 1781. The three nebulae, nos. 98, 99 & 100, are very difficult to recognize, because of the faintness of their light: one can observe them only in good weather, & near their passage of the Meridian.

William Herschel

[PT 1814, p. 248-284, here p. , reprinted in Scientific Papers Vol. II, p. 528]
Connoiss. 100 is "A nebula of about 10' in diameter, but there is in the middle of it, a small, bright cluster of supposed stars."

John Herschel (1833): h 1211.

h 1211 = M100.
Sweep 422 (April 28, 1832)
RA 12h 14m 17.9s, NPD 73d 14' 34" (1830.0) [Right Ascension and North Polar Distance]
p B; R; p s m b M. Not a very remarkable nebula. II.84 was not seen.
Pretty bright; round; pretty suddenly much brighter toward the middle. Not a very remarkable nebula. H II.84 [NGC 4328] was not seen.

Sweep 418 (April 21, 1832)
RA 12h 14m 19.3s, NPD 73d 13' 39" (1830.0)
Barely visible through cloud.

Sweep 25 (May 6, 1826)
RA 12h 14m 20.8s, NPD 73d 13' 26" (1830.0)
v L; s m b M; a nucleus with dilute borders
Very large; suddenly much brighter toward the middle; a nucleus with dilute borders.

Sweep 421 (April 26, 1832)
...., NPD 73d 13' 56" (1830)
v F; v L; R; v s b M to a p B nucleus
Very faint; very large; round; very suddenly brighter toward the middle to a pretty bright nucleus.

Smyth: CCCCXLV [445]. M100.

CCCCXLV. 100 M. Virginis [now Comae Berenices].
AR 12h 14m 52s, Dec N 16d 42'.6
Mean Epoch of Observation: 1837.21 [Mar 1837]
A round nebula, pearly white, off the upper part of the Virgin's left wing, and certainly at a great distance from Virgo's ear of corn, where the Connaissance des Temps places it [actually Messier's position is quite close]: indeed, the true site will be hit upon just one-fifth the way from Beta Leonis towards Arcturus. This is a large but pale objects, of little character, though it brightens from its attenuated edgestowards the centre; and is therefore proved to be globular. It was discovered by M. Méchain in 1781, and is accompanied by four small stars, at a little distance around it; besides minute points of light in the field, seen by occasional gleams.
We are now in the broad grand stratum of nebulae, which lies in a direction almost perpendicular to the Galaxy [Milky Way], and passes from the south, through Virgo, Berenices Hair, Canes Venatici, and te Great Bear, to the Pole, and beyond. This glorious but mysterious zone of diffused spots, is an indisputable memorial to all future times, of the unwearied industry and indomitable scientific energy of Sir William Herschel. Yet has this unrivalled contributor to knowledge been disparagingly described, as a man indulging in "speculations of no great value to astronomy, rather than engage in computations by which the science can really be benifited." Save the mark! This is said of a philosopher of zeal and application hitherto unequalled: one whose contributions to the Philosophical Transactions prove the bold but circumspect grandeur of his conceptions, his consummate mechanical resources, and the exactness of his elaborate calculations. Herschel's labour, however, transcended those of the ages in which he was cast, although he gave such animation and bias to siderial astronomy that his mantle was caught at.

John Herschel, General Catalogue: GC 2890.

GC 2890 = h 1211 = M100.
RA 12h 15m 50.6s, NPD 73d 23' 54.0" (1860.0) [Right Ascension and North Polar Distance]
!!; (H,h) pF; vL; R; vg, psbMrN; (L) 2-branched spiral. 5 observations by W. & J. Herschel.
Very remarkable; (W. & J. Herschel) pretty faint; very large; round; very gradually, then pretty suddenly brighter toward the middle where there is a mottled nucleus; (Lassell) 2-branched spiral.

Lassell

[Memoirs of the Royal Astronomical Society, Vol. XXXVI (36)]
[Drawing on Plate III, Fig. 17]

Dreyer (1877)

GC 2890, h. 1211 [M 100]. Drawing in Lassell, Plate III, Fig. 17.

Dreyer: NGC 4321.

NGC 4321 = GC 2890 = h 1211; Méchain, M 100.
RA 12h 15m 50s, NPD 73d 24.0' (1860.0) [Right Ascension and North Polar Distance]
!! pF, vL, R, vg, psbMrN, (L) 2-br spir; = M100
Very remarkable, pretty faint, very large, round, very gradually, then pretty suddenly brighter toward the middle where there is a mottled nucleus, (Lassell) 2-branched spiral.
Remark: Figure in Lass 2 [Lassell, Memoirs R.A.S. vol. xxxvi], plate III, fig. 17.

Curtis

[Descriptions of 762 Nebulae and Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 4321, RA=12:17.8, Dec=+16:23. [Publ. Lick Obs.] Vol. VIII, Plate 35. A bright, regular, nearly round spiral 5' in diameter. Very faint stellar nucleus surrounded by bright, short whorls, forming a central oval. Tje outer whorls are rather open, quite regular, and show many stellar condensations. Two novae [actually supernovae] have appeared in this spiral. M. 100. 15 s.n.