David Dunlap Observatory

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The David Dunlap Observatory (DDO) is an astronomical observatory, located on a 189-acre site in Richmond Hill, Ontario, and donated to the University of Toronto by Jessie Donalda Dunlap as a memorial to her husband David. When it opened in 1935, its 74" (1.88m) reflecting telescope was the second-largest in the world. The DDO came about as a result of the indefatigable efforts of Professor C.A. Chant who, in his many public lectures and writings, had extolled the benefits of an astronomical observatory for the University and for the city. David Dunlap, a lawyer and philanthropist who had become wealthy as a result of mining ventures in Northern Ontario, had attended one of Chant's lectures in 1921, and expressed an interest in the project, but passed away in 1924 before any concrete steps were taken. In 1926, Chant tactfully approached his widow, and she expressed a strong interest in the project. As was the custom in those days, the observatory was located well outside the city, but close enough so the staff could commute to their home, and to the campus. The observatory opened, with great ceremony, on May 31, 1935, Chant's 70th birthday, as a facility for research, undergraduate and graduate student training, and public education. Chant was Director for a day, then was replaced by R.K. Young.

The 1.88m "great" telescope was instrumented for stellar spectroscopy, a field of research that was well suited to the site, given its less-than-perfect weather. The DDO specialized in systematic measurement of the radial (line of sight) velocities of stars using the Doppler effect, and the study of the orbits of binary stars using the same technique. Spectroscopic studies of the nature of both normal and peculiar stars were also carried out. The telescope was also used for photographing and studying variable stars, especially by Professor Helen Sawyer Hogg. In the 1930's, a 0.5m (19') telescope was installed in a dome on the administration building, and equipped and used for photometry, starting in 1947. In 1966, a 0.6m (24") telescope was added, and equipped for both photometry and for spectroscopic classification of stars, a field of expertise of Professor Robert Garrison. An 8" refracting telescope was installed in a third dome in 1951, and used for instruction of students; it was moved to the National Museum of Science and Technology in 1984. Under the direction of Donald MacRae, small radio telescopes were installed on the grounds, and used for student training, and research in this developing field. The 1960's and 1970's were very active and productive decades for DDO. About two dozen graduate students completed thesis projects using the 1.88m telescope, some of them also making use of the two smaller photometric telescopes. The most newsworthy (and significant) research project was the co-discovery, by Tom Bolton, of the first black hole in space. This project, like many other DDO projects, was successful because it required regular, sustained access to a well-instrumented telescope, something that was not possible at remote observatories.

Although the DDO worked closely with the Town of Richmond Hill to control light pollution, the use of the DDO for research and student training declined. Most faculty and students did their observational research at observatories with better sky conditions, or worked in other branches of astronomy. The McLaughlin Planetarium and the Ontario Science Centre became the main centres for public astronomy education in the Toronto area, although the DDO public and school programs continued, in partnership with the Toronto branch of the Royal Astronomical Society of Canada.

The recent history of the DDO has been turbulent, and its status and future are still uncertain. In 2008, the University sold it to a developer, Metrus Development Inc. The proceeds were used to endow a new Dunlap Institute for Astronomy and Astrophysics (DI), to carry the Dunlap name and bequest into the 21st century. There were objections from the community, both from a few professional and amateur astronomers who felt that the DDO still had a role to play in astronomy, and from local citizens who wished to preserve the property as greenspace. Since 2009, the Toronto branch of the Royal Astronomical Society of Canada has voluntarily and successfully offered public education programs, using the telescope and auditorium, notably on Saturday evenings in the summer, and is developing a business plan to offer an expanded, year-round public and school education program.


Heard, J.F. and Hogg, H.S. (1967), Astronomy at the David Dunlap Observatory, Journal of the Royal Astronomical Society of Canada, 61, 211-238.

Jarrell, R.A. (1988), The Cold Light of Dawn: A History of Canadian Astronomy, University of Toronto Press.