Dominion Astrophysical Observatory

1.8-metre Plaskett Telescope

Planning for the construction of this telescope was initiated in 1910 by John Stanley Plaskett, who also performed most of the design work. Grinding and polishing of the optics in Pittsburgh, Pennsylvania by John Brashear started in 1914 and was completed in 1918. Work on the mechanical components of the telescope and dome in Cleveland, Ohio, began in 1915 and was completed in 1916. Upgrades to its instruments and detectors in recent years have increased its sensitivity by a factor of about 10,000 over its original capabilities.

The Plaskett telescope is 15 metres in length and the moving parts of the telescope weigh 42 tonnes. The telescope can perform optical and near infrared imaging as well as spectroscopy (study of the rainbows of the stars).

The telescope was originally built to study the motions of stars through the use of its spectrograph, for the purpose of studying the structure of the Milky Way and the masses of stars, but is now used for a wide variety of projects. Early studies of stellar motions led to the discovery of one of the most massive stars known, Plaskett's Star, and showed the orbital motion of our solar system about the centre of the Milky Way Galaxy. Understanding of the orbital motion of the solar system, combined with studies using the telescope estimating the amount of interstellar material, led to size and mass estimates for the Milky Way.

Nowadays, the telescope is used to determine the orbits of comets and asteroids, study the nature of stars, learn more about distant objects like quasars and galaxies, and carry out many other research projects.