David Dunlap Observatory

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.

Located on a hill, yet still relatively close to sea level at 730 ft. (238 m) above sea level, and now surrounded by subdivisions, optical astronomy ability has been reduced as compared to other remote observatory sites around the world. Nevertheless, the DDO can still be used for spectral astronomy and 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.

Read more about David Dunlap Observatory:  DDO 74 Inch (188 Cm) Telescope Contemporaries On Commissioning

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