The Richmond Hill David Dunlap Observatory (RHDDO) houses the largest telescope in Canada. A number of important studies have taken place here, including providing the first direct evidence that Cygnus X-1 was a black hole, pioneering measurements of the distance to globular clusters and the discovery that Polaris was stabilizing.

To visit the RHDDO, pre-registration is required in one of our programs or workshops. We offer a variety of family programs, such as summer and virtual astronomy programs, heritage tours, and lectures where participants can explore the night sky, discover the cosmos and learn about the history of this unique National Historic Site!