Plaque(s)

Description of Historic Place

Dominion Astrophysical Observatory National Historic Site of Canada is located at the top of a hill, 227 metres above sea level in Victoria, British Columbia. The observatory, built from 1914 to 1918, is a cylindrical structure 20.2 metres in diameter and 22.3 metres high that is topped by a domed roof with two arched slats that open to allow the telescope to focus on the night sky. The distinguished two-storey steel frame building is clad in painted white metal panels, and features classically inspired architectural embellishments such as pilasters, stringcourses, and arches. Official recognition refers to the footprint of the observatory building.

Heritage Value

The Dominion Astrophysical Observatory was designated a National Historic Site of Canada because: it is a world-renowned observatory where many discoveries about the nature of the Milky Way galaxy were made, using the observatory's 1.83-metre reflecting telescope and spectroscopes, and where collaborative research with international observatories gave Canadian astronomers an important international role; it was built using the world's most advanced design for an observatory, after extensive consultation at the international level, and was remarkable for its accuracy, clarity of optical lenses, and spectroscopes, thus improving measurements of radial velocities, spectroscopic parallaxes and spectroscopic orbits; it is directly associated with the work of Canadian astronomer John Plaskett, who discovered at the observatory the largest known solar binary mass in 1922, and with many other notable and internationally respected Canadian astronomers who used the observatory to better understand the universe and improve the technical equipment used in land-based observatories; its otherwise pragmatic metal-clad exterior features pilasters, entablatures and other classically inspired architectural embellishments applied to its steel-framed structure.

The Dominion Astrophysical Observatory (DAO) was built following new developments in reflecting telescope technology during the early 20th century. In 1914 Canadian astronomer and the first DAO director, John S. Plaskett, designated a National Historic Person of Canada, successfully lobbied the federal government for funding to build a new observatory with a very powerful reflecting telescope. From the time of its completion in 1918 until the 1960s it was one of the world’s main astrophysical research centres.

Many discoveries were made using the observatory’s 1.83-metre reflecting telescope and spectroscopes at DOA. The most important early work was the identification and classification of higher temperature stars. In 1922, Plaskett discovered a spectroscopic binary that was four times larger than any previously discovered. During the 1920s and 1930s, the DAO also produced in-depth studies on the nature of star evolution and motions in space, which notably added to the understanding of the rotation of the Milky Way and how stars age. Much of the DAO’s work was focussed on specific classes of stars, for which the observatory and Canadian astronomers received international attention.

The DAO was constructed using the world’s most advanced design for an observatory in the early 20th century. The 1.83-metre telescope, remarkable for its accuracy, clarity of optical lenses and spectroscopes, was a major engineering accomplishment and briefly the largest in the world. The focal ratio of the telescope was ideal for the stellar spectroscopy at the Observatory, and its asymmetrical mount gave it access to most of the sky, the first of this type for a reflecting telescope. Electrical drives were avoided in favour of precise and traditional mechanical movement with roller ball bearings, allowing for a more reasonable cost without losing precision.

Sources: Historic Sites and Monuments Board, Minutes, December 2008; Report - Dominion Astrophysical Observatory, Saanich, British Columbia, 2008-057.

Character-Defining Elements

The key elements that contribute to the heritage character of the site include: its remote hilltop location in Saanich, British Columbia; its strategic siting 227 metres above sea level; its simple cylindrical massing topped by a domed roof with two arched slats that open to allow the telescope to focus on the night sky; the building shell, designed to be structurally light and allow for easy rotation; its exterior metal cladding, painted white with blue accents; its projecting entrance portico consisting of blue double doors, a round-arched transom, flanking columns that support a small pedimented roof, detailed with stringcourses and an entablature of the Dominion of Canada coat of arms above the door pediment on the front porch; the classically inspired architectural embellishments applied to its steel-framed structure such as the stringcourses, pilasters and arches; its massive poured-in-place reinforced concrete H-shaped pier for the telescope, rising approximately ten metres from the foundation; its 1.83-metre reflecting telescope, including the telescope mirror, the asymmetrical shaped mounting and the fixed spectroscope shielded in a solid box and covered in a temperature case; the interior features, including the original steel wheels connected to weights and pulleys used to rotate the dome; the round drum with riveted side panels, pilasters and double windows accented in blue; the nine-and-one-half ton polar axis; the original telescope control equipment, including the roller ball bearings that support the polar and declination axes of the telescope, the device used for changing mirrors to function in different operational modes and the optical lenses; its functional interior layout with the ground storey holding the vacuum mirror-coating machine and the drum’s pulleys; and the upper storey, which is built around the telescope’s pier and holds the telescope equipment, the former darkroom and a computer room; its original terrazzo floors, including the inscription referring to the intended 1916 opening of the observatory.