High Quality Content by WIKIPEDIA articles! The David Dunlap Observatory (DDO) is a large astronomical observatory site located just north of Toronto in Richmond Hill, Ontario within a 189-acre (76 ha) estate. Formerly owned and operated by the University of Toronto from its establishment in 1935 until 2008, the observatory is now managed by the Royal Astronomical Society of Canada, Toronto Centre. Its primary instrument is a 74-inch (1.88 m) reflector telescope, at one time the second largest telescope in the world, and still the largest in Canada. Several other telescopes are also located at the site, which formerly included a small radio telescope as well.