David Dunlap Observatory

Introduction

The David Dunlap Observatory (DDO) sits in Richmond Hill, Ontario, Canada, at 123 Hillsview Drive, about a 40-minute drive north of downtown Toronto. It is a public observatory and destination park in the Greater Toronto Area that combines scientific heritage, historic architecture and woodland. History: the observatory was promoted by University of Toronto astronomer Clarence Chant and endowed by Jessie Donalda Dunlap, widow of the mining financier and keen amateur astronomer David Alexander Dunlap, in his memory. The main building was designed by the Toronto firm Mathers and Haldenby, and the steel dome was built by Grubb-Parsons in England. It was officially opened on 31 May 1935; Canada's prime minister, William Lyon Mackenzie King, called it 'a gift to science all over the world.' Telescope and mirror: the 74-inch (1.88 m) reflector, completed in 1935, was then the second-largest optical telescope in the world (after the 100-inch telescope at Mount Wilson Observatory) and remains the largest optical telescope in Canada. Its primary mirror weighs 23 tonnes, was the first Pyrex mirror blank ever cast, and served as the test blank for the 5-metre telescope at Palomar Observatory. The tube is over 10 m long, and visitors climb a spiral stair inside the dome to see it up close. Research: from 1935 to 2007 the site stood at the forefront of Canadian astronomy, with work in radio astronomy, the distance to globular clusters and the stability of Polaris. In 1972 astronomer Tom Bolton used the 1.88 m telescope to obtain the first direct evidence that Cygnus X-1 is a black hole. Notable Canadian astronomers such as Helen Sawyer Hogg also worked here. Heritage status: in September 2009 Richmond Hill designated the property under the Ontario Heritage Act (By-law 100-09), and in 2019 the federal government recognised it as a National Historic Site. From university to city: the University of Toronto sold the property to a developer in June 2008, prompting a long community and heritage battle. After Ontario Municipal Board mediation, Richmond Hill received about 40 hectares (99 acres) of parkland together with the dome and Administration Building in 2017; the whole property is about 76.5 hectares (189 acres). Today: now run by the City of Richmond Hill for public education and outreach. Each spring, summer and fall (roughly late May to late October) visitors can take free self-guided tours of the Administration Building and dome. Stargazing parties are free and usually need no booking but are weather dependent. The RASC Toronto Centre also runs night-time observing and digital planetarium (Starlab) programmes, and there are summer science camps. Woodland trails around the observatory are open year-round for daytime walks. Location note: this observatory is in Ontario, Canada, not David, Panama; the two share a Chinese translation but are in different countries, so check the itinerary carefully.

✨ Highlights

🛈 Practical Info