By Robert Hawkes
This spring the Plaskett Telescope, located on Observatory Hill in Saanich, marked 100 years. First light at the telescope was May 6, 1918. Parks Canada recently unveiled a plaque recognizing the telescope as a National Historic Site, joining historic sites in this area such as Emily Carr House and St. Ann's Academy. The historic site designation recognizes the significance of the telescope in establishing Canada as one of the leaders in global astronomy. The lobby of the Royal BC Museum currently has on display a 1/10 scale model of the telescope. That model was built prior to observatory construction in order to test the mechanical design.
For several decades the telescope was one of the largest in the world, slightly smaller than the Mount Wilson Observatory in California that opened about the same time, and larger than the telescope at Harvard College Observatory. Some of the most important astronomical work of the period was done with the Plaskett Telescope. Having such an important facility here attracted a lot of public attention, and it has been estimated that in the 1920s up to 30,000 people per year visited the observatory.
You really have to be under the Plaskett Telescope to truly appreciate its scale. The larger mirror is just over 1.8 m in diameter and the telescope tube is 15 m long. The mobile parts of the telescope that must precisely track astronomical objects weigh more than 40 tons. The telescope continues in use to this day.
The telescope was equipped with a spectrograph that allowed precise measurements of the colour of light. Light that is slightly shifted to the red indicates a source moving away from us, while light shifted to the blue is from a source moving towards us. This is analogous to the case for sound - a siren moving towards us is a higher pitch than one moving away. By studying these light colour shifts the motion of stars and other astronomical objects can be inferred.
Observations conducted at the telescope provided the first clear indications of motion within our galaxy and established our position in the Milky Way spiral galaxy. Binary star systems (two stars in orbit about each other) are valuable astrophysical tools, and for many decades the largest known binary system was that first studied in the early years of the Plaskett Telescope.
With our many cloudy nights from fall until late winter, one might wonder how Victoria came to be chosen as the location for a major optical telescope. Five sites were tested: Ottawa, Medicine Hat, Banff, Penticton and Victoria. While Ottawa, where a more modest telescope was already in operation, would have been the most cost effective, Victoria was deemed "undoubtedly the most suitable site for a large reflecting telescope." The resolution of earth-based telescopes are limited by the slight dancing of images due to air turbulence caused by atmospheric temperature changes. With much more constant temperatures, Victoria produces more stable astronomical images. Lobbying for the project began in 1911, and construction took place from 1914 to 1918.
The telescope is named after John Stanley Plaskett (1865-1941), who conceived of the design, supervised its construction, and served as the first director of the observatory. He had a somewhat unconventional academic career, only deciding to start an undergraduate degree at age 30, after having served as a machinist for a number of years creating physics demonstration equipment for the University of Toronto. He moved directly from that degree to work as an astronomer, first in Ottawa and then here in Victoria.
Many honours were bestowed on John Stanley Plaskett. The telescope was renamed in his honour in 1993. The massive binary star system he first studied was named Plaskett's Star (only a very few stars are named after people), and both an asteroid and a crater on the moon also carry his name.
The home for Canada's national research in astronomy and astrophysics, the Herzberg Institute of Astrophysics (HIA), was moved from Ottawa to Saanich in 1995. In 2001 the research activities were complemented by a new astronomical outreach arm termed the Centre of the Universe. Government budget cuts resulted in the outreach centre closing in 2013. However, through a nonprofit foundation and volunteer staffing, the outreach effort continues on a more limited scale.
Any Saturday evening this summer you have the opportunity to see the telescope yourself. The non-profit Friends of the Dominion Astrophysical Observatory (DAO) in conjunction with the Royal Astronomical Society of Canada (RASC) are hosting summer star parties each Saturday evening until September 1. Each evening includes "Out of this world" interactive presentations, planetarium-based stories of the skies, tours of the Plaskett telescope, night-sky viewing when weather permits, as well as other family friendly astronomical activities. Some weeks there are also guest talks. While there is not a cost to attend the Saturday star parties, tickets must be obtained in advance. Information and ticket reservations are available at https://thecentreoftheuniverse.net/star-parties. The events take place no matter what the weather.
As Victoria RASC Centre President Chris Purse wrote "The selection of Victoria as the home of the Dominion Astrophysical Observatory meant that Victoria became the centre of astronomy in Canada." Why not get close to this piece of Canadian history some Saturday evening this summer?