At Harvard College Observatory, Jim collaborated with Donald H. Menzel, Lawrence H. Aller, and George H. Shortley on a landmark series of papers on the physical processes in gaseous nebulae. In addition to this theoretical work, Jim began designing a set of astronomical instruments with increasing resolving powers and wide field angles. In 1945, he was co-author, with George Z. Dimitroff, of Telescopes and Accessories. His design for the Baker-Schmidt telescope and the Baker Super Schmidt meteor camera were notable accomplishments.

In 1941, while still a graduate student, Jim was awarded a small research contract by U.S. Army Col. George W. Goddard to develop a wide-angle reconnaissance camera at the Harvard College Observatory. The next year, this project was expanded to produce huge quantities of an f/2.5 lens capable of covering a 5x5-inch photographic plate. More than 100 other projects were subsequently developed, with lenses up to 12 inches in diameter.

As director of the Observatory Optical Project at Harvard University from 1943 to 1945, Jim spent thousands of hours doing calculations on a Marchant calculator to produce his aerial cameras. He provided the optical designs, supervised the optical and machine shops, and risked his life operating cameras in early test flights that carried these photographic systems in unpressurized compartments. During this time, he also began a long consulting career with the Perkin Elmer Corporation. When World War II ended, Harvard University decided to terminate its war-related projects, and Jim’s lab was moved to Boston University. The lab later became the basis of ITEK Corporation.

Jim was an associate professor and research associate at Harvard from 1946 to 1949. In 1948, he received the Presidential Medal of Merit for his work in the Office of Scientific Research and Development during World War II, as well as an honorary doctorate from the University of Louisville. That year, he also moved to California to spend two years as a research associate at Lick Observatory. He returned to Harvard in 1950.

To speed up the tedious process of design calculations, Jim introduced numerical computers into the field of optics. His ray-trace program was one of the first applications run on the