Great Telescope Dome, 1935, Grubb, Parsons & Co., Richmond Hill, ON.
© Jennifer A. Cousineau, Parks Canada, 2018

When it opened in 1935 in what was then an isolated setting 20 kilometres north of Toronto in Richmond Hill, Ontario, the David Dunlap Observatory (DDO) featured the world’s second-largest telescope and was central to establishing academic astronomy in Canada. The long-term project of C.A. Chant, “the father of Canadian astronomy,” the Observatory was home to generations of astronomers at the University of Toronto, combining a mandate of teaching, research, and public accessibility. Through his research at the DDO, astronomer Thomas Bolton achieved a major astronomical breakthrough when his research confirmed the existence of black holes in 1971. The DDO was financed by Jessie Donalda Dunlap, who named it in memory of her late husband. It comprises two principal buildings: the Great Telescope Dome, a fine and well-preserved example of early to mid-20th century observatory design in Canada which successfully combines Modern and Neo-Classical elements, and the elegant Beaux-Arts Administration Building, designed by the architecture firm of Mathers & Haldenby, and in keeping with other designs for buildings for the University of Toronto.

As an educational centre, the DDO immediately strengthened the discipline of astronomy in Canada. While the federal government had funded two observatories – the Dominion Observatory in Ottawa and the Dominion Astrophysical Observatory in Victoria – the lack of university facilities meant that there were still no opportunities for Canadian students to receive practical astronomical training during their education. As a result, the University of Toronto was the first Canadian school to offer graduate degrees in astronomy, with the first doctorate awarded in 1953.

The research conducted at the DDO has informed hundreds of publications, but one stands out as the most significant of these. In the summer of 1971, postdoctoral researcher Thomas Bolton found evidence of a black hole in the middle of the Milky Way. This was a major astronomical development as a black hole had never been identified and his original article confirming its existence is an important contribution to astronomy.

The DDO’s most striking visual feature is the Great Telescope Dome, often simply called “the observatory.” It is a massive domed structure, the primary function of which is to form a protective envelope for the 74 inch reflecting telescope it houses. It is painted white and comprises a set of raised, retractable shutters for astronomical viewing, characteristic of astronomical architecture throughout the 20th century. Located northeast of the observatory and reached via a paved processional pathway is the Administration Building. This stately structure is a restrained Beaux-Arts composition. Echoing the architecture of the Dome, the Administration Building features three symmetrically-disposed domed turrets, each of which once housed a functioning telescope (one of which still does). These smaller domes made the Administration Building a second location at the site for astronomical research and a place where students could be trained without having to compete with research astronomers for time in the larger dome.