The Building and Early History of DAO


In 1910, Canadian astronomer John Stanley Plaskett embarked with a bold vision to modernize the national astronomy program with a 'great' reflecting telescope, culminating in the construction of the Dominion Astrophysical Observatory (DAO) in Victoria, BC.

In 1914, the Canadian federal government formally approved Victoria as the location for the proposed 72" reflector, intended to be the largest in the world, due to the city's stable size and moderate climate. Residents welcomed the institution, with the May 13, 1914 Colonist remarking that "nothing can add more to the attractiveness of the city," and "Victoria will become a scientific centre."

The new project fostered interest from scientists and the public alike, as Victorians visited the project site and expressed support for the proposed facility. Premier Richard McBride and the Province of British Columbia welcomed the opportunities presented by the unprecedented instrument, financing the property and supplying a road for the new institution.


Despite delays caused by the First World War, construction proceeded rapidly between 1914 and 1918, with growing anticipation from the national and international scientific communities. Materials were transported up the hill by horse and buggy. The 5,000-pound mirror barely escaped the calamity of the Great War, and was shipped from Antwerp just three days before the conflict broke out. The building and telescope mounting were ready by the fall of 1916, but the project was delayed when the John A. Brasher Company encountered issues shaping the 72" mirror.

Despite the delays, the Victoria observatory quickly developed into a tourism destination, with thousands of visitors making the journey to see the mechanical parts of the telescope before its official opening in June 1918.

The engineering of the telescope was also key to success at the DAO. Although the telescope weighed a massive 64 tons, it could be adjusted with the slightest touch. An astronomer working with a night assistant was able to mobe the telescope and begin exposing a new target within two minutes - far faster than contemporary instruments.

Early Operation

The DAO opened in 1918 with a skeleton crew of J.S. Plaskett and R.K. Young, who immediately began observations with the largest operational telescope in the world. In coordination with the Mt. Wilson Observatory in California, they began an ambitious 800 star multi-year observing run on their specialty - binary stars. They were joined by William Harper in 1919; using the efficient new telescope they were able to expose 1800 photographic plates and measure 1000 of them by the time Harper arrived. Plaskett's son, Harry, returned from the Great War in 1919, reaching the observatory in August. He immediately participated in the binary star observing program, and over the following years made several exciting contributions to stellar spectroscopy.

Local & International Recognition

The discovery of Plaskett's star in December 1921 marked a rare moment where public interest nearly matched the DAO astronomers' fascination with binary stars. The flurry of publications and widespread press coverage marked the 'arrival' of DAO science for the international community, producing an enduring reputation of excellence.

During the early 1920's, the daily Colonist ran bi-weekly 'Astronomy Talks' columns to inform Victorians on the progress of science at the facility. This practice continued throughout the 1930's as W.E. Harper embraced the latest technology to conduct regular broadcasts over the CFCT Wireless on current understandings in astronomy.

The telescope was widely visited throughout the 1920's, hosting tourists, visiting scientists, and contributing to incredible astrophysical discoveries. Despite being eclipsed in size by the Hooker 100" telescope on Mt. Wilson, the DAO remained the largest telescope an 'ordinary visitor' could look through. Due to extensive engagement efforts, public interest in the telescope steadily increased throughout the 1920's. In 1925, Plaskett reported that 25,000 visitors had travelled to the DAO each year since it was built. By 1929, this figure increased to nearly 40,000.

Continuing Projects

In 1922, astronomer R.K. Young represented the DAO on an eclipse expedition in Australia. The Canadian team captured several clear images, and successfully measured the gravitational bending of starlight passing the sun, thus confirming the expectations of Einstein's Theory of General Relativity.

With the completion of the initial binary star program, the staff at DAO began to investigate one of the biggest puzzles of astrophysics: the structures of the Milky Way galaxy. R.K. Young produced tentative results on clouds of interstellar calcium, soon followed by several papers from Plaskett himself.