I had the opportunity on Saturday night to go inside the David Dunlap Observatory to see the telescope. At 74 inches (1.88 meters) in diameter and almost a foot thick, the mirror in this telescope makes it the largest in Canada. The entire telescope structure weighs 23 tons, including the two-ton mirror, and was built in 1935. It is completely mechanically operated – no computers! – and is rotated into position by physically turning wheels and pushing buttons.