elements (a special mirror, a diaphragm at a particular location, and a "correction plate") into a simple catadioptric system, based on reasoning from first principles, was epoch making. In particular, the "correction plate" was like nothing ever seen before in telescope design. After Schmidt a flood of new catadioptric designs appeared in the subsequent decades. Last years Schmidt built his first "Schmidtspiegel" (which came to be known as the Schmidt camera) in 1930, a breakthrough which caused a sensation around the world. He employed a very clever method (the so-called "vacuum pan" method) to make the difficult "corrector plate", so that the system gave superb images. The vacuum pan involved carefully warping a parallel glass plate under partial vacuum into a slight sagging curve and then polishing the upper curve flat. After release of the vacuum, the lens would spring back into the "Schmidt shape" needed for the camera. No one had ever made a lens in this way before. Schmidt published a brief account (in German) of his invention in professional publications, and offered to build his cameras for professional observatories. Unfortunately, his publicity was too little and his design was too novel. Moreover, the invention coincided with the beginning of the Great Depression. No orders came in and he remained dependent on Schorr and Bergedorf for a modest income from occasional jobs till the end of his life. He produced a larger camera in 1934 and reground the 60 cm Bergedorf-Steinheil photographic refractor as well. Schmidt fell ill at the end of November 1935 after a business trip to Leiden in the Netherlands. Despite attempts at treatment, he died on 1 December 1935 in Hamburg at the age of 56. An autopsy revealed that he was suffering from a lung infection. Personal life and legacy Schmidt did not marry and had no children. Soon after his death, through the advocacy of Walter Baade when he arrived at the Mount Wilson Observatory in the United States, the Schmidt telescope idea took off. An 18" Schmidt was produced in 1936 and then twelve years later, the famous 48" (122 cm) Samuel Oschin telescope Schmidt-telescope was built at Mount Palomar Observatory. This last telescope produced a flood of new observations and information. It proved the brilliance of the Schmidt concept beyond doubt. Subsequently at Bergedorf in 1955 a large, well-constructed Schmidt was dedicated. The 2-meter Schmidt telescope of the Karl Schwarzschild