Otto Struve discovered NGC 3739 on 16 Mar 1869 with the 15-inch refractor at Pulkovo Observatory in St. Petersburg. He recorded "Very faint nebula, situated in the middle between several small stars. Almost on a straight line between two stars (mag 11-12), little closer to the south one, from which the PA is 327 °. From the more northern star it is 160 °. Distance between the two stars from each other is about 4'." He found this object (along with 7 others) while searching for Comet Winnecke (7P/Pons-Winnecke) in Mar-Apr 1869.

400/500mm - 17.5" (5/4/02): very faint, very elongated 3:1 SSW-NNE, 0.6'x0.2', very low even surface brightness. Located 12' W of mag 7.0 HD 100843 (very close double?).

Notes by Steve Gottlieb