page_title: David Dunlap Observatory
section_title: Construction
hierarchical_section_title: David Dunlap Observatory / History / Construction
caption_attribution_description: English: Guests at telescope open house.
context_page_description: The David Dunlap Observatory is an astronomical observatory site just north of Toronto, in Richmond Hill, Ontario, housed on a 189-acre 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, and the David Dunlap Observatory Defenders. Its primary instrument is a 74-inch 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 also included a small radio telescope. The legacy of the David Dunlap Observatory continues in the Dunlap Institute for Astronomy & Astrophysics, a research institute at the University of Toronto established in 2008.
  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.
context_section_description: Chant immediately started ordering a telescope, selecting a 74-inch (1.9 m) instrument from Grubb, Parsons and Company in England. This would make it the second-largest telescope in the world, second only to the 100-inch (2.5 m) instrument at Mount Wilson Observatory. It was, however, only slightly larger than the one that had recently gone into service for the Dominion Astrophysical Observatory in British Columbia, at 72 inches (1.8 m). The observatory building itself started construction, and the eighty-ton sixty-one-foot (18.6 m) copper dome was built by Grubb and Parsons in 1932 and arrived in 1933. The administration building, a few hundred feet from the main observatory, also started construction and designed by Mathers & Haldenby Architects. The 76-inch (1.9 m) mirror blank (the two outermost inches (5 cm) of the mirror are not used) was supplied by Corning Incorporated and cast in Pyrex from a batch of glass that Corning also used to produce the 200-inch (5.1 m) mirror for Palomar Observatory. Chant and Mrs. Dunlap attended the pouring of the mirror at the factory in Corning, NY in June 1933. The mirror was annealed, then shipped to Grubb-Parsons in England for polishing. The telescope was completed in time for the finished mirror's return in May 1935.
  The official opening was on 31 May 1935, Chant's 70th birthday. The opening ceremony was attended by notables such as Sir Frank Dyson, former Astronomer Royal, and former Prime Minister William Lyon Mackenzie King, who praised the Observatory as "a gift to science all over the world." Chant retired the same day and moved into Observatory House, the original pre-Confederation farmhouse (built in 1864 for Alexander Marsh and known also as Elms Lea Alexander Marsh) just to the south of the administration buildings, where he spent his remaining years.  In May, 1939 the train carrying King George VI and Queen Elizabeth, the Queen Mother on their cross-Canada tour paused on the railway below the observatory, the largest telescope in the commonwealth.
  Grubb-Parsons built four more 1.88-metre telescopes with similarities to the instrument in Richmond Hill: for Radcliffe Observatory near Pretoria, Mount Stromlo Observatory in Australia, Helwan Observatory in Egypt, and an observatory in Okayama Prefecture in Japan. The South African instrument was disassembled and moved to Sutherland, Northern Cape in the 1970s because of light pollution. The original telescope mirror at Helwan was replaced by Zeiss in 1997, and the telescope at Mount Stromlo was destroyed by fire in 2003. A 1.93-metre Grubb-Parsons telescope at Haute-Provence Observatory with a higher-resolution spectrograph was used to discover an extrasolar planet orbiting the star 51 Pegasi in 1995.
  The three smaller domes on the top of the DDO administration building are used for smaller instruments. Soon after the observatory opened in 1935, a 50 cm Cassegrain reflector telescope was installed in the southern dome. The 6-inch (150 mm) Cooke Refractor had been out of use since the Meteorological Office had given it to Hart House, but it was little used and was moved into the northern dome in 1951 to be used by undergraduates. Much later, in 1965, a similar 60 cm Cassegrain was added to the central dome.
caption: Queue at the observatory in 1935, when guests were invited to inspect the telescope
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