William Herschel discovered NGC 5846 = H I-128 = h1901, along with NGC 5845, on 24 Feb 1786 (sweep 532) and recorded "vB, pL, bM. With one preceding NGC 5845] just [at edge of field]; and 5' more north, and vF, R. I saw also a third small one preceding." The "third small one preceding" might refer to NGC 5839, which has a separate log entry or Wolfgang Steinicke suggests it might apply to NGC 5846A, the very close companion on its south side. On 13 Apr 1838, John Herschel logged "B; R; psbM to nucleus; 30" [diameter]."

John Herschel's first observation of NGC 5846 was on 29 May 1821 while being instructed on sweeping techniques by his elderly father. His Aunt Caroline recorded the observation: "F; R; gmbM; resolvable; appears to have 2 nuclei; south following in the same field is a very small, round nebula." James South also took a look and exclaimed (quoted in JH's journal), "O! Good God! It is worth going to the devil for! The second nuclei is NGC 5846A. This short sweep (4 objects) was later registered out of order as sweep 53. He observed NGC 5846 again the next night (sweep 54) and noted "The neb of last night with the 2 nuclei." Guillaume Bigourdan also resolved the companion and noted Big. II-75 as "round, stellar centre, forms a very close companion to 4045 G.C. [NGC 5846]."

In addition, Edward Burton, observing with LdR's 72" on 25 Apr 1868, logged "h1901 [NGC 5846] is double, 3rd Nucleus suspected on n side." The third nucleus is a faint star. On 3 May 1877 Dreyer also noted "companion nebula [to NGC 5846] vS, less than 1' south." But the following year he commented "small star (NOT a nebula) involved south." This was likely the reason Dreyer did not enter NGC 5846A into the NGC. DeVaucouleurs introduced the NGC 5846A designation in the RC I.

400/500mm - 17.5" (5/10/91): bright, moderately large, oval 3:2 NNW-SSE, 3'x2', evenly concentrated as halo brightens down to a small bright core but no nucleus, fainter halo. Forms a contact pair with NGC 5846A (appears as a mag 13.5 "star") embedded in the southern portion of halo 40" from the center! Brightest in a group with NGC 5850 10' ESE and NGC 5845 8' WNW.

600/800mm - 24" (6/23/17): at 375x; very bright, moderately large, round, 1.5'-2' diameter. Sharply concentrated with an intensely bright nucleus that increases to the center. Large, round halo gradually fades at periphery. NGC 5846A is situated on the south side of the halo and appeared moderately bright, high surface brightness but very small and round, 15" diameter.

24" (6/14/15): bright, fairly large, round, 1.8' diameter, sharply concentrated with a very bright core. The outer halo has a low surface brightness. NGC 5846A is on the south side of the halo [44" from center]. It appeared as a fairly faint compact glow, round, 15" diameter, fairly high surface brightness. A much fainter mag 15.5 star is superimposed 25" N of center. NGC 5850 lies 10' SE.

Notes by Steve Gottlieb