BIG MIRROR: It was 40 years ago that a huge mirror was
manufactured at Corning Glass Works for a telescope being made in
British Columbia.

And we mean “huge”: The fused silica mirror blank was 157 inches
in diameter, 25 inches thick and weighed about 18 tons.

At the time, it was the second largest telescope disc made by
Corning. Largest was the 200-inch disk, made of borosilicate glass
in 1934 for the Hale Telescope at Mount Palomar.

The telescope, of course, is one of the key inventions in the
field of astronomy, opening up previously unknown sights in our
solar system. And with ever larger telescopes, our knowledge of the
universe has grown exponentially.

One key development was the introduction of the mirror which
expanded on the reach of a simple lens as the heavens were
explored. And technological innovations made the mirrors ever more
crucial to the science.

The April 14, 1970, Era included a photo of what was then the
world’s largest fused silica telescope mirror. We reported:

“The mirror will be used as the primary optical component of the
Queen Elizabeth II Telescope.

“Corning said the University of British Columbia and six other
universities in western Canada are spearheading a drive to build
the telescope atop 6,100-foot-high Mount Kobau, 250 miles east of
Vancouver in the Richter Pass.”

For this behemoth to make the 2,700-mile trip to Vancouver was
quite a feat.

“The Canadian disk will be loaded aboard a special depressed-bed
railroad car for the trip, expected to take about two weeks. It is
encased in a blue and white steel package standing 15 feet high, 16
feet long and 10 feet wide and weighing about 56,000 pounds.

“Semi-finished, the Queen Elizabeth blank has a flat-bottom
surface, a saucer-shaped curve on the top side and a 29 3/4-inch
diameter hole in the center.

“In Vancouver, the blank will go to the optical shop of the
University of British Columbia where it will be ground and polished
and coated with a thin film of aluminum.

“Corning said fused silica  — one of the purest of manmade
materials — was used for the mirror blank because of its thermal
stability, hardness and mechanical strength and finishing
properties. The material also is transparent so that astronomers
and engineers can inspect its internal structure.”