What was Alan Hale's best known co-discovery formally designated as? 
Alan Hale (astronomer): is an American professional astronomer, best known for his co-discovery of Comet Hale–Bopp along with amateur astronomer Thomas Bopp. Comet Hale–Bopp: Comet Hale–Bopp (formally designated C/1995 O1) is a comet that was perhaps the most widely observed of the 20th century, and one of the brightest seen for many decades.
C/1995 O1