History of the Dominion Observatory

The Dominion Observatory (DO) was established in part to provide the most accurate time possible. The time at a prime meridian is key to determining longitude and, as Greenwich had become the prime meridian for the World, the DO in Ottawa became the prime meridian of Canada in 1905. All surveys in Canada referred back to the observatory.

Determining time required a transit telescope to observe the moment a star crossed ("transited") the north/south line of the sky (the meridian). Several transit telescopes have been used at the DO and the one shown is one of the smaller. However, time was not the only responsibility of the new observatory. The government had appropriated $375,000 for the facility, which was to include a 15-inch refracting telescope. This was intended not to determine time, but for astrophysical studies.

The surfaces of the two elements that made up the 15-inch lens were accurate to a millionth of an inch. The original lens was replaced in 1958 with a triple element lens, still the largest of its type ever fabricated.

The telescope was originally housed in a copper covered dome at the Central Experimental Farm (CEF) in Ottawa. The astronomers had a variety of instruments at their disposal including a prism spectrograph, cameras and filar micrometer for measuring stellar positions.

The building and dome still exist at the CEF, but after the Dominion Observatory closed in 1970, the telescope was moved to the Canada Science and Technology Museum. It remains the largest refractor ever erected in Canada.
Canadian Heritage Information Network
Canadian Heritage Information Network, Canada Museum of Science and Technology, Musée de la civilisation, Stewart Museum, Canadian Medical Hall of Fame, Museum of Health Care at Kingston, University Health Network Artifact Collection, University of Toronto Museum of Scientific Instruments, University of Toronto Museum Studies Program, Suzanne Board, Dr. Randall C. Brooks, Sylvie Toupin, Ana-Laura Baz, Jean-François Gauvin, Betsy Little, Paola Poletto, Dr. James Low, David Kasserra, Kathryn Rumbold, David Pantalony, Dr. Thierry Ruddel, Kim Svendsen

© 2001, CHIN. All Rights Reserved.

Teachers' Centre Home Page | Find Learning Resources & Lesson Plans