[1][2] After graduation, he joined the staff of the Lick Observatory on Mount Hamilton as an assistant to Dr. William Wallace Campbell.
From 1909 to 1913, he was in charge of the observatory's southern station in Chile before returning to the United States.
He spent many years performing radial velocity measurements of stars, which culminated in 1928 with the publication of a general catalog.
In 1944 he began to suffer health issues because of the observatory's altitude, and so resigned as director in 1948.
[1] Prior to his death, he and Dr. F. J. Neubauer released the Fifth Catalogue of the Orbital Elements of Spectroscopic Binary Stars.