Scope and Contents These materials are loosely grouped and described based on their nature and use. Their description may be fully refined as more is learned about them. The Hayden Planetarium at the American Museum of Natural History opened on October 3, 1935. Since its inception, the Planetarium has served as an educational and exhibition platform and as the face of the Department of Astronomy, known as the Department of Astronomy and American Museum-Hayden Planetarium after 1953. The Hayden...