For a number of years I lived a block away from “The Ob” as it was known then. It’s nice to know that the instrument is preserved, but with all the artificial light in the city there’s not much to see.
Respect must be paid to Alvan Clark, who learned to grind lenses in middle age, and produced quite a few for observatories around the country. The 40 objective for the Yerkes was his largest. Working without computers and lasers, it was quite a feat.
“Respect must be paid to Alvan Clark, who learned to grind lenses in middle age, and produced quite a few for observatories around the country. The 40 objective for the Yerkes was his largest. Working without computers and lasers, it was quite a feat.”
He did that with his hands, too. Worked his fingers to the bone - literally. So his kids took over.
Allegheny Observatory, Part of The University of Pittsburgh, has, I believe, the third largest refractor, called the “Thaw” when I was a student there. It has a 30-inch lens, magnificent.
They also have a large collection of plates which are used in parallax and proper motion calculations. I think they have well over 100,000 plates dating back to the 1920’s or so.
They also have a 13-inch Clark refractor, with a gravity drive. It is shown to visitors along with free, guided tours of the historical place.