Dominion Astrophysical Observatory

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Dominion Astrophysical Observatory
The Dominion Astrophysical Observatory, located on Observatory Hill, in Saanich, British Columbia, was completed in 1918 by the Canadian government. Proposed and designed by John S. Plaskett in 1910 with the support of the International Union for Cooperation in Solar Research, when the 72-inch aperture telescope was constructed, it was planned to be the largest telescope in the world but delays meant it saw first light after the Hooker 100-inch telescope.

Centre of the Universe
Centre of the Universe is the public interpretive centre for the observatory. The centre features interactive exhibits about astronomy, the work of the observatory and its parent organization, the NRC Herzberg Institute of Astrophysics. There are also tours of the telescope and programs in the planetarium and video theatre.

Telescope construction
The building that houses the telescope was built by McAlpine-Robertson Company of Vancouver for a price of $75,000. Both the building and dome, made by Warner and Swasey Co, are double walled. The mirror weighs approximately 2000 kilograms and was made by the Saint-Gobain company in their Charleroi glass works in Antwerp, Belgium and shipped only a week before the start of World War I. It was then ground in the United States at the John A. Brashear company in Pittsburgh. The mirror had to be reground twice, once due to a mysterious scratch and the 2nd time due to a flaw in the grinding. This added 2 years to the completion time of the telescope, pushing the date back to 1918. The completed mirror was hauled up Little Saanich Mountain by horse and wagon.

Use
Following completion, Plaskett remained the head of the observatory until 1935. A spectrograph is fitted to the Cassegrain focus and an imaging CCD is attached to the Newtonian focus. In 1962, a 48" optical telescope was added to the observatory. The telescope, ordered in 1957, was made by Grubb Parsons of Newcastle-upon-Tyne, England. Its Coude focus is used with a room sized specrograph. In 1995, the observatory was made the headquarters of the NRC Herzberg Institute of Astrophysics, which operates several Canadian telescopes, both optical and radio, as well as shares in international telescopes, such as the Canada-France-Hawaii Telescope. The telescopes are in constant use today and are open for visitors year round. An interpretive centre called the Centre of the Universe was opened in 2002. As of July 2009, the current director was Dr James E Hesser.

Plaskett telescope contemporaries on commissioning
The Plaskett missed becoming the largest telescope in the World, but remained the second largest until the 74 inch (188 cm) reflector at David Dunlap Observatory in 1935 (also in Canada) debuted. Top 2 in 1918:

The next largest were the Harvard College Observatory 60 inch and the Mt. Wilson 60-inch Hale.

# Name / Observatory Image Aperture Altitude First Light Special advocate 1 Hooker Telescope Mount Wilson Obs. 100 inch 254 cm 1742 m (5715 ft) 1917 George Ellery Hale Andrew Carnegie 2 Plaskett telescope Dominion Astrophysical Obs. 72 inch 182 cm 230 m (755 ft) 1918 John S. Plaskett