NGC 3503 (also ESO 128-EN28 and OCL 833) is a magnitude +9.4 open star cluster with an emission nebula located in the constellation Carina.
The cluster was discovered by British astronomer John Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at the Cape of Good Hope on the 1st April 1834.
Right Ascension 11h 01m 17.2s, Declination -59° 50' 50"
