From 1920 until his death he worked for the Meudon Observatory, where in 1930 he earned the title of Joint Astronomer of the Observatory. After gaining the title, he earned a reputation of being an expert of polarized and monochromatic light. Throughout the 1930s, he labored to perfect the coronagraph, which he invented to observe the corona without having to wait for a solar eclipse. Most of this work implied painstaking long observations at the Pic du Midi Observatory. It was an exceptionally good site, free of both air pollution and light pollution but it came with a disadvantage: In the interwar period access to the peak implied mountaineering skills and physical fitness, especially in winter when access was only gained with a long and tiresome ski touring trek on sealskin-fitted skis, a technique mastered by Lyot, a keen sportsman and mountaineer.[2] Accommodation on site can only be described as spartan, before a powerline, a bigger refuge and a cablecar were built in the early 1950s. In 1938, he showed a movie [3] of the corona in action to the International Astronomical Union. In 1939, he was elected to the French Academy of Sciences. He became Chief Astronomer at the Meudon Observatory in 1943 and received the Bruce Medal in 1947.
