This is how you make a telescope mirror out of a hunk of glass: Use a sand mixture and another piece of glass to grind away the middle of a concave shape. Repeat with finer and finer grit sand. Dave Barosso demonstrates the technique, but to do it yourself, try to visit one of the Telescope Makers Workshop‘s classes on Friday nights in Oakland.
“They’re the type of people who love to work with their hands,” Barosso says of telescope lens makers. One of the attractions is the price; a couple of chunks of glass are cheap, especially compared to the price of a large store-bought telescope.