The collection contains Seth Barnes Nicholson's astronomical research and correspondence. The majority of Nicholson's research material deals with his study of Jupiter and its moons . His other research includes his study of magnetic activity, the asteroid Icarus, Trojan asteroids, Pluto, Venus, the Sun and Sun spots. There are some pieces of correspondence in the research folders. Most of the correspondence is between Nicholson and other astronomers throughout the world; the majority of it is also about Jupiter and its moons, asteroids and sun spots. Notable participants in the collection include: Giorgio Abetti, Astronomical Society of the Pacific, Robert Grant Aitken, Joseph Ashbrook, Ira Sprague Bowen, Leland E. Cunningham, Sturla Einarsson, Charles Federer, Paul Herget, Samuel Herrick, Theodor S. Jacobsen, Vladimir Kourganoff, Karl Otto Kiepenheuer, Gerard Kuiper, Willem Luyten, M. G. J. Minnaert, Yngve hman, Jan Oort, William Henry Pickering, Frederick Hanley Seares, Harlow Shapley, Otto Struve, Alexander N. Vyssotsky, Fred L. Whipple and Fritz Zwicky. The collection also includes several photographs.