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The Dunlap Observatory

The Story

The David Dunlap Observatory was built in 1935 featuring one of the most powerful optical telescopes in the world, a 74-inch (1.9-metre) reflector model. In this 1969 report from CBC-TV's The Day It Is, we take a short tour of the observatory and get a detailed description of the telescope and how it works.

Medium: Television
Program: The Day It Is
Broadcast Date: July 15, 1969
Guest: Gerry Longworth
Interviewer: George Finstad
Duration: 7:45

Did You know?

• The Dunlap Observatory was named after its financial backer, David Dunlap, who died in 1924. He was a wealthy Canadian businessman with a keen interest in astronomy. Clarence Chant, who was head of the Royal Astronomical Society of Canada at the time, sought the support of the City of Toronto and local businessmen to build a new observatory in the region. Dunlap's widow agreed to support its construction in memory of her husband.


• Key discoveries at the Dunlap Observatory include the confirmation of a black hole in 1972 by Thomas Bolton. Known in astronomy as Cygnus X-1, the hole was 11,000 light years away from Earth by Bolton's calculations. You can learn more about the first black hole in an essay by Bruce Rolston in The Bulletin, the newsletter of the University of Toronto.


• Gerry Longworth was lead technician at the observatory who worked with Helen Hogg as early as 1935. After serving in the Canadian Navy, he returned to the observatory following the Second World War.


• In 2008, the University of Toronto sold the land and the observatory buildings to Metrus Development Inc., a property developer. In 2009, an agreement was reached between Metrus and the Royal Astronomical Society of Canada to maintain the observatory. It reopened on Earth Day.



Astronomy: Canadian Stargazers more