The collection is composed primarily of correspondence between Dr. Pogo and members of the general public with an interest in astronomical issues and the work of the Mount Wilson Observatory. Consists of a large number of letters from school-age children with questions about the workings of the universe. Other correspondence includes questions from amateur astronomers as well as a number of queries about the relationship between astronomy and religious issues, particularly biblical prophecies. Other subjects include flying saucers, space travel, expeditions to the moon, observations of the sky, comets, eclipses, and new planets. The collection also includes a number of letters from amateur and professional astronomers from around the world, particularly Europe and Latin America. Generally, the letters were not addressed directly to Dr. Pogo but were forwarded to him from the Observatory's administrative offices for replies.