The only way to get rid of "stars" around blown-out highlights is to have an aperture without overlapping leaves--either a waterhouse stop or a lens used wide open (although a few lenses still have blades exposed even wide open.)

This is one of the reasons I like my Mamiya 50/6.3 on 6x9 so much for night work--it's so slow (and wide) that you actually have a lot of DOF wide open, and it's certainly sharp wide open as well. If only it were multi-coated....