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The David Dunlap Observatory is home to the largest optical telescope on Canadian soil with a primary mirror measuring more than 1.88 metres (74 inches) in diameter.

Constructed in the 1930s, the Observatory is located in the heart of Richmond Hill, Ontario. The dome building is 18.6 metres (61 feet) in diameter and the rotating dome weighs 73 metric tons. The telescope itself weighs 21 metric tons (without its primary mirror).

The DDO is located at 123 Hillsview Drive in Richmond HIll. Hillsview can be reached from Bayview Avenue, north of 16th Ave. If driving on Highway 404, from the north use exit #31 Major MacKenzie, or from the south exit #29 16th Ave. If driving the 407, use exit #77 Yonge or exit #79 Bayview. Public transit options are limited. A nearby bus stop is on YRT route 86 at the corner of Essex Ave and Weldrick Rd E. The Richmond Hill GO station is to the north, about 2 km away.
David Dunlap Observatory
123 Hillsview Drive
Richmond Hill, ON, L4C 1T3
Phone Number
43' 51' 46" N
79' 25' 21" W
There is parking for regular events. Parking will be restricted for major open house events.