They cast the mirror in 1935, brought it to Cal Tech in 1936, finished assembling the telescope in 1939, tested and adjusted it for another ten years (they took

They cast the mirror in 1935, brought it to Cal Tech in 1936, finished assembling the telescope in 1939, tested and adjusted it for another ten years (they took a break to fight World War 2), and so it was not until 1949 that they got the first image out of it. Very soon the telescope would discover that the Andromeda galaxy was twice as far as we'd thought. The giant lens is still there and is still making discoveries today. It found a new mini-moon of Jupiter in 2010.