Lawrence Parsons, 4th Earl of Rosse, discovered NGC 5755, along with NGC 5752 and 5753 on 1 Apr 1878, while observing NGC 5754. He noted a faint nebula in PA 18.3° from NGC 5754 at a distance of 131.8" (the actual separation is closer to 3', although the PA is accurate).

WH probably discovered this object earlier on 16 May 1787 (sweep 738). In his discovery of NGC 5754 = H III-687, he noted "Another much fainter and smaller suspected, about 2 [arcmin] more north. 300 shewed the same." Because of his uncertainty, he didn't assign NGC 5755 an internal discovery number and WH missed being credited with the discovery.

400/500mm - 17.5" (6/21/93): last of four in the NGC 5754 quartet. Very faint, small, round, 25" diameter, even surface brightness. A mag 13 star lies 1' SE. Forms a close pair with NGC 5753 1.9' NW and the NGC 5752/5754 pair is just 3' SSW.

Notes by Steve Gottlieb