Contains biographical materials, correspondence, publications and appearances, printed materials, and photographs. The bulk of the collection consists of correspondence documenting his professional activities, and photographs documenting the building and instrumentation of Steward Observatory at The University of Arizona, and Kitt Peak National Observatory in the Quinan Mountains, west of Tucson, Arizona. Selected correspondents include Bart Bok, Raymund Dugan, Sture Holm, Knut Lundmark, Otto Struve, and Harlow Shapley.
1917 to 1963
1930 to 1960