Heinrich d'Arrest discovered NGC 588 = Au 13 in M33, along with NGC 592, on 2 Oct 1861 with the 11-inch Fraunhofer refractor in Copenhagen. His micrometric position (measured on several nights) is accurate. Auwers included this HII region in his 1862 catalogue of 50 new nebulae.

300/350mm - 13.1" (7/5/86): barely visible with averted. Almost collinear with NGC 592 and NGC 595.

400/500mm - 17.5" (7/5/86): extremely faint nebulosity in M33, requires averted vision to view. Located 14' W of the center of M33 and forms the western vertex of a very obtuse isosceles triangle with NGC 592 6' E and NGC 595. Nearly collinear with NGC 592 and the core of M33. This is a HII region and star cluster.

Notes by Steve Gottlieb