Caption: Guido Horn d'Arturo (1879--1967) and the world's first working segmented mirror which he built in 1952. The Horn d'Arturo segmented mirror telescope had 61 hexagonal segment mirrors and a 1.8-meter diameter (Wikipedia: Guido Horn d'Arturo: Segmented mirror telescope). It was a zenith telescope, and so it always pointed to zenith and was NEVER slewed (Wikipedia: Guido Horn d'Arturo: Segmented mirror telescope). Since it did NOT slew, the segments were held rigidly in place and did NOT use active optics to hold the segments to the precise parabolic reflector shape. The individual segments were, in fact, spherical mirrors, but they were arranged to give an overall parabolic reflector shape (Wikipedia: Guido Horn d'Arturo: Segmented mirror telescope)???.
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