[PT 1814, p. 276, SP2 p. 536] Sept. 24, 1810. Large 10 feet Newtonian telescope. Space penetrating power 75.82. Magnifying powers 71, 108, 171, 220. "The 3rd of the Connoiss. [M3, NGC 5272] is one of the globular clusters; very brilliant and beautiful. The compression of the stars begins to increase pretty suddenly from the outside at 3/4 of the radius, and continues gradually up to its centre, its diameter taking in the outside is full half of the field of the glass magnifying 171 times, giving 4'30"."

[PT 1818, p. 436, SP2 p. 595]
The 3rd of the Connoissance.
"1813, 7 feet finder of the telescope. It is at a small distance from a star of equal brightness ; the star is clear, the object is hazy, and somewhat larger than the star."
"1783, 7 feet telescope. With 460 the light is so feeble that the object can hardly be seen; I suspect some stars in it. 1813, with 80, many stars are visible in it."
"1799, 10 feet telescope, power 120; with an aperture of 4 inches it is resolvable; with 5 easily resolvable; with 6 it is resolvable; with 7 and all open the stars may be easily perceived."
"1784, 1785, 20 feet telescope. A beautiful cluster of stars, about 5 or 6 minutes in diameter."
"1810, Large 10 feet telescope. With 171 the diameter is full 4'30". (*)" (*) see above observation from [WH 1814].
By the observation of the 7 feet telescope this cluster must be of the 243rd order.

John Herschel - 1833 - h 1663 -

h 1663 = M3.
Sweep 417 (April 20, 1832).
RA 13h 34m 12.2s, NPD 60d 46' 22" (1830.0) [Right Ascension and North Polar Distance]
A most superb object, diam = 10s.0 time in RA. Not less than 1000 stars 11m and under. They run into a blaze at the centre, and form as it were radiating lines and pointed projections from the mass, with many stragglers.

Sweep 64 (March 26, 1827).
RA 13h 34m 18.0s, NPD 60d 45' 51" (1830.0)
I just see the stars through a cloud so thick as almost to obscure Arcturus; 6' diam, but in a clear night no doubt more.

Sweep 415 (April 17, 1832). RA 13h 34m 18.1s, NPD 60d 46' 8" (1830.0)
Observed with Capt. Smyth, who "saw something remarkable" in a small * 2m or 3m preceding it, which proved on closer examination to be a fine first class double *.

Sweep 65 (March 30, 1827). RA 13h 34m 19.5s, NPD 60d 45' 46" (1830.0)
Very beautiful; stars 11 .... 15m; fills field, making lines and irregular rays of stars, and coming up to a blaze in the middle.

Sweep 343 (April 13, 1831). RA 13h 34m 20.7s, NPD 60d 45' 38" (1830.0)
A noble globular cluster 5 or 6' diam, entirely resolved when not a star near it, even Arcturus, was visible to the naked eye for clouds.

William Henry Smyth: CCCCXCII [492]. M3

CCCCXCII. 3 M. Canum Venaticorum.
AR 13h 34m 45s, Dec N 29d 10'.6
Mean Epoch of Observation: 1831.26 [Apr 1831]
[with drawing]
A brilliant and beautiful globular congregation of not less than 1000 small stars, between the southern Hound and the knee of Boötes; it blazes splendidly towards the centre, and has outliers in all directions, except the sf [south following; SE], where it is so compressed that, with its stragglers, it has something of the figure of the luminous oceanic creature called Medusa pellucens. This noble object is situated in a triangle formed by three small stars in the np [north preceding; NW], nf [north following; NE], and sf [south following, SE] quadrabts, which, by their comparative brightness, add to the beauty of the field. It is nearly in mid-distance between Arcturus and Cor Caroli, at 11deg north-west of the former star. brp> This mass is one of those balls of compact and wedged stars, whose laws of aggregation it is so impossible to assign; but the rotundity of figure gives full indication of some general attractive bond of union. It was discovered in 1764 by Messier, who described it as "a nebula without a star, brilliant and round:" his instrument must have been rather moderate not to resolve this object, and it is matter of regret, that the exertions of such a man were straitened to such means. It was next pronounced to be a "mottled nebulosity;" but in 1784, Sir W. Herschel attacked it with his 20-foot reflector, and resolved it into a "beautiful cluster of stars, about 5' or 6' in diameter." By the gauging process, which he has fully described, he estimated its profundity to be of the 243rd order.

John Herschel, General Catalogue: GC 3636.

GC 3636 = h 1663 = M3.
RA 13h 35m 40.8s, NPD 60d 55' 6.0" (1860.0) [Right Ascension and North Polar Distance]
!!; Glob. Cl.; eB; vL; vsmbM; st 11 ... 14 observations by W. & J. Herschel.
Very remarkable; globular cluster; extremely bright; very large; very suddenly much brighter toward the middle; stars of 11th magnitude and fainter.

William Huggins:

[Further Observations on the Spectra of some Nebulae, with a Mode of determining the Brightness of these Bodies. Phil. Trans. Roy. Soc., Vol. 156 (1866), p. 381-397; here p. 389]
[No. [GC] 3636. 1663 h. 3 M. R.A. 13h 35m 40s. N.P.D. 60d 55' 6". Cluster; extremely bright.]
"Ein leicht auflöslicher Hauf zahlloser Sterne, in der Mitte zu einem einzigen Lichte von grosser Helligkeit zusammenlaufend." [An easily resolvable cluster of innummerable stars, converging to a single light of great brightness in the middle.] - D'Arrest
Spectrum continuous

Heber Doust Curtis:

[Descriptions of 762 Nebulae and Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 5272, RA=13:37.6, Dec=+28:53. [Publ. Lick Obs.] Vol. VIII, Plate 48. M. 3. The main portion of this beautiful cluster is about 8' in diameter. 1 s.n.