David Dunlap Observatory

David Dunlap Observatory

The 74-inch (1.9 m) telescope at the David Dunlap Observatory
Organization	University of Toronto (1935–2008) Royal Astronomical Society of Canada (2009–)
Code	779
Location	Richmond Hill, Ontario, Canada
Coordinates	43°51′44″N 79°25′21″W / 43.86222°N 79.42250°W / 43.86222; -79.42250
Altitude	224 m (735 ft)
Weather	67% clear nights[1]
Established	31 May 1935
Website	astro.utoronto.ca/DDO/ www.theddo.ca/
Telescopes
Telescope 1 1.88 m reflector Telescope 2 0.6 m Cassegrain Telescope 3 0.5 m Cassegrain
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astro.utoronto.ca/DDO/

The David Dunlap Observatory (DDO) is a large astronomical observatory site just north of Toronto in Richmond Hill, Ontario, housed on 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.

The DDO is the site of a number of important studies, including pioneering measurements of the distance to globular clusters, providing the first direct evidence that Cygnus X-1 was a black hole, and the discovery that Polaris was stabilizing and appeared to be "falling out" of the Cepheid variable category. Located on a hill, yet still relatively close to sea level at 730 feet (220 m) altitude, and now surrounded by subdivisions, its optical astronomy ability has been reduced as compared to other remote observatory sites around the world.

The DDO owes its existence almost entirely to the efforts of one man, Clarence Chant. Chant had not shown an early interest in astronomy, but while attending University College, University of Toronto he became interested in mathematics and physics, eventually joining the university as a lecturer in physics in 1892. Over the next several years he worked as a schoolteacher and civil servant. During a later leave of absence he earned his PhD from Harvard University and did postdoctoral work in Germany.