Messier 105

Discovered by Pierre Méchain on March 24, 1781.
Independently rediscovered by William Herschel on March 11, 1784.

Méchain: M105.

(in his letter to Bernoulli, May 6, 1783)
Mr. Messier mentions there on page 264 and 265 two nebulous stars, which I have discovered in the Lion [Leo; M95 and M96]. I find nothing to correct for the given positions which I have determined by comparison of their situation with respect to Regulus. There is, however, a third one, somewhat more northerly, which is even more vivid [brighter] than the two preceding ones [M95 and M96]. I discovered this one on March 24, 1781, 4 or 5 days after I had found the other two. On April 10, I compared its situation with Gamma Leonis from which followed its right ascension 159d 3' 45" and its northern declination of 13d 43' 58".

William Herschel: H I.17.

I.17. Mar. 11, 1784. [Together with I.18 = NGC 3384]
The 2 p of 3. Both vB. cL. mbM. C. II 41. Fig. 4.
The 2 preceding of 3. Both very bright. Considerably large. Much brighter toward the middle. Compare H II.41 [NGC 3389]. Figure 4.

[1811: PT Vol. 1811, p. 226-336; here p. 289]
Of treble, quadruple, and sextuple Nebulae.
If it was supposed that double nebulae at some distance from each other would frequently be seen, it will now on the contrary be admitted that an expectation of finding a great number of attracting centers in a nebulosity of no great extent is not so probable; and accordingly observation has shewn that greater combinations of nebular than those of the foregoing article [Of double Nebulae at a greater Distance..] are less frequently to be seen. The following list however contains 20 treble, 5 quadruple, and 1 sextuple nebulae of this sort. (*) See treble nebulae. [including H I.17 = M105].

John Herschel (1833): h 757.

h 757 = H I.17.
Sweep 338 (April 4, 1831)
RA 10h 38m 50.1s, NPD 76d 31' 33" (1830). [Right Ascension and North Polar Distance]
vB; pL; R; psvmbM; 50"; r. The first of 3.
Very bright; pretty large; round; pretty suddenly very much brighter toward the middle; 50" diameter; mottled. The first [western-most] of 3 [nebulae].

Sweep 234 (February 19, 1830)
RA 10h 38m 50.5s, NPD 76d 32' 14":: (1830).
vB; R. The first of 3.
Very bright; round. The first of 3.

Sweep 240 (March, 1830)
RA 10h 38m 50.7s, NPD 76d 31' 24": (1830).
vB; L; R; psbM; 50". The first of 3. (Seen also in Sweep 2).
Very bright; Large; round; pretty suddenly brighter toward the middle; 50" diameter. The first of 3. (Seen also in Sweep 2).

Smyth

[in his description of H I.18 = NGC 3384, his No. CCCLXXXVII (387)]
A pair of bright-class nebulae, sp [south preceding, SW] and nf [north following, NE] of each other, on the Lion's belly, discovered by WH [William Herschel] in March, 1783, and No. 758 [NGC 3384] in his son's Catalogue; while at a small distance to the nf [north following, NE] is a neat but minute double star. These are two of the three nebulae described by both Herschels [M105 and NGC 3384]; but the third [NGC 3389] I cannot distinguish, unless it be a glow in the sf [south following, SE], in a vertical line with two small stars. We now approach a region where these mysterious luminous massesare scattered over the vast concavity of the heavens, in truly boundless profusion; and in them, all true Herschelians must view mighty laboratories of the Universe, in which are contained the principles of future systems of suns, planets and satellites!
The objects here treated of, are among the nebulae included within a round patch of about 2deg or 3deg in diameter, in the apparently starless space of the Lion's loins. Now the observer unprovided with an equatorial instrument - and unfortunately many of Urania's most zealous followers are in that predicament - may wish to fish it up. If his telescope be of capacity for grasping sufficient light, the field may be found, under a moderate power, south of the line which joins Regulus and Theta Leonis about 10 deg east of, and nearly on the parallel with, the former.

John Herschel, General Catalogue: GC 2203.

GC 2203 = h 757 = H I.17; Mechain.
RA 10h 40m 25.7s, NPD 76d 41' 10.7" (1860.0) [Right Ascension and North Polar Distance]
vB; cL; R; psbM; r 6 observations by W. & J. Herschel.
Very bright; considerably large; round; pretty suddenly brighter toward the middle; mottled.

Dreyer: NGC 3379.

NGC 3379 = GC 2203 = h 757 = H I.17; Méchain.
RA 10h 40m 26s, NPD 76d 40.9' (1860.0) [Right Ascension and North Polar Distance]
vB, cL, R, psbM, r; = M105
Very bright, considerably large, round, pretty suddenly brighter toward the middle, mottled.

Curtis

[Descriptions of 762 Nebulae and Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 3379, RA=10:42.6, Dec=+13: 7. This, with [NGCs] 3384 and 3389, forms a striking group, a right-angled triangle whose shorter sides are 7' long. [NGC] 3379 is nearly round, 2' in diameter; very bright; no spiral structure discernible. 33 s.n.

Helen B. Sawyer [Hogg]: Identification of M105

[in Astronomical Journal, Vol. 53, p. 117 (1948)] ".. a long-overlooked letter by Pierre Méchain was found in Bode's Jahrbuch for 1786. .. He also lists four nebulae which he has discovered, and these should logically be given Messier numbers as follows: NGC 4594 as M104; NGC 3379 as M105; NGC 4258 as M106; and NGC 6171 as M107. .."