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Chapters: Yrjö Väisälä, Anders Johan Lexell, Liisi Oterma, Esko Valtaoja, Mauri Valtonen, Nils Mustelin, Arto Oksanen, Heikki A. Alikoski, Virpi Niemelä, Hugo Gyldén, Anders Donner, Hilkka Rantaseppä-Helenius, Seppo Mikkola. Source: Wikipedia. Pages: 45. Not illustrated. Free updates online. Purchase includes a free trial membership in the publisher's book club where you can select from more than a million books without charge. Excerpt: Yrjö Väisälä ( (help·info)) (6 September 1891 21 July 1971) was a Finnish astronomer and physicist. His main contributions were in the field of optics, but he was also very active in geodetics, astronomy and optical metrology. He had even an affectionate nick-name of Wizard of Tuorla (Observatory/Optics laboratory), and there is a book with the same title in Finnish describing his works. His brothers were mathematician Kalle Väisälä and meteorologist Vilho Väisälä. Väisälä was also a fervent supporter of Esperanto, presiding as the president of the Internacia Scienca Asocio Esperantista ("International Association of Esperanto Scientists") in 1968. He developed several methods for measuring the quality of optical elements, as well as a lot of practical methods of manufacturing said elements. This allowed the construction of some of the earliest high-quality Schmidt cameras, in particular a "field-flattened" version known as Schmidt-Väisälä camera. Contemporary to Bernhard Schmidt's design, but unpublished was also Prof. Yrjö Väisälä's identical design which he had mentioned in lecture notes in 1924 with a footnote: "problematic spherical focal surface". Once he saw Schmidt's publication, he promptly went ahead and "solved" the field flattening problem by placing a doubly-convex lens slightly in front of the film holder (back in the 1930s, astronomical films were glass plates.) The resulting system is known as the Schmidt-Väisälä camera or sometimes as the Väisälä camera. (This solution is not...More: http://booksllc.net/?id=173278 ... Read more