William O'Brien Observatory

The William O'Brien Observatory in Marine on St. Croix, Minnesota.
Photo credit
Cass0114 under CC BY-SA 3.0

The William O'Brien Observatory (OBO) is a facility in Marine-on-St. Croix, MN, owned and operated by the University of Minnesota. OBO a 30", f/10, Cassagrain telescope, opened in the spring of 1968.