Three Partners Build a Telescope
The Canada–France–Hawaii Telescope (CFHT) is a 3.6-metre optical telescope built jointly by the National Research Council of Canada, the French National Centre for Scientific Research and the University of Hawaii. It stands near the summit of Mauna Kea on the island of Hawaii. The partners established the telescope corporation in 1974 and began construction on the mountain; 1979 marked first light and the dedication.
The 1974 environmental impact statement and the tripartite agreement it contains set out the partners’ responsibilities. Canada and France provided the main construction work and funding for the telescope, basic instruments, dome and supporting facilities. The University of Hawaii arranged use of the site and contributed roads and a mid-level station. A board and scientific advisory bodies shared management responsibilities. Observing time was allocated 42.5 percent to Canada, 42.5 percent to France and 15 percent to Hawaii.
Why Mauna Kea?
Mauna Kea’s high altitude, relatively stable clear air and dry conditions favoured optical and infrared observations. Its low latitude gave Canadian astronomers access to southern regions of the sky that were difficult to observe from Canada. Its longitude in the central Pacific also made the observatory a useful participant in continuous observations involving widely separated stations.
High-altitude conditions increased the burden of transporting equipment, maintaining facilities and working on site. Roads, accommodation and work facilities already established by the University of Hawaii reduced the cost of creating new support infrastructure. The project linked the summit telescope with facilities at lower altitude. Both observing conditions and practical logistics shaped its feasibility.
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From the Mirror to the Focal Stations
The primary mirror was made from Cer-Vit, a glass-ceramic material with low thermal expansion. It was ground and polished at the Dominion Astrophysical Observatory in Victoria, British Columbia, then coated with a thin layer of aluminium to reflect starlight. Aperture determined the telescope’s light-gathering capacity, while the mirror’s shape, support and tracking system had to work together to preserve sharp images.
In their early instrumentation paper, engineer Pierre Bely and astronomer Gérard Lelièvre identified good image quality and efficient use of observing time as major design goals. The telescope used a parabolic primary mirror and could accommodate equipment at the prime, Cassegrain and coudé foci. The prime focus served direct imaging, while the coudé optical path directed light to a relatively fixed location for spectroscopic work.
First Light and Gradual Commissioning
The primary mirror arrived in Hawaii in March 1979. The telescope saw first light that August, and the dedication took place on September 28. Its focal stations and observing equipment then entered service in stages. In a September 1980 report, director Roger Cayrel stated that visiting astronomers had begun observing at the prime focus in March of that year.
A wide-field corrector designed by Charles Wynne expanded the usable field at the prime focus to nearly one degree, allowing photographic plates to record star fields and galaxies. Bely and Lelièvre subsequently reported that the coudé focus entered operation in October 1980. The telescope progressively broadened its observing configurations from direct imaging to spectral analysis.
Structures Revealed on Photographic Plates
Cayrel’s early report described Sidney van den Bergh’s observations of NGC 3928. The new images resolved spiral arms that had not previously been clearly identified, revealing a miniature spiral structure in a galaxy formerly classified as elliptical or lenticular. The report also reproduced a one-hour exposure of the elliptical galaxy NGC 4472, surrounded by numerous globular clusters. Its caption gave stellar image diameters of 0.7 to 0.9 arcseconds.
Early research also used prime-focus imaging to investigate structures around quasars and speckle interferometry to study Pluto and Charon. Photography and different detectors allowed the same telescope to record celestial signals on different scales and of different kinds. Sharp images, stable tracking and instrument selection together determined the detail that observations could resolve.
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Engineering and Cooperation Behind the Observations
Maintaining the mountain observatory was demanding. Cayrel noted that insufficiently dried air in the primary mirror’s pneumatic support could allow moisture to condense, freeze and block pipes. Thermal disturbances inside the dome also affected image quality. Cooling pipes in the dome floor helped control the internal temperature. The favourable mountain environment had to be matched by mirror support, thermal control and daily maintenance.
Visiting observations, routine repairs and installation of new instruments all drew on limited staff. Institutions in Canada, France and Hawaii supplied observers and developed photometers, spectrographs and detectors. Through this continuing cooperation, usable prime-focus imaging was followed by expanded spectroscopic and infrared configurations, turning a multinational construction project into a long-running research facility.