He also served as a summer volunteer at the Yerkes Observatory.

In the 1950s he worked a few years at the Yerkes Observatory.

He accepted a position at the Yerkes Observatory in 1924 and worked there until his retirement in 1939.

He then emigrated to the United States and joined the staff of the Yerkes Observatory.

He joined Yerkes Observatory in 1909 as an assistant, and remained there until 1911.

He worked at Yerkes Observatory for much of his career, including acting as its director from 1960 to 1963.

He was the research assistant at the Yerkes Observatory for the summer of 1919.

Yerkes Observatory is the setting for about seven minutes of the 1996 movie Chain Reaction.

Astronomers at the Yerkes Observatory waited until just prior to dawn to observe and photograph it.

The earliest known photograph of Pluto was taken, although the astronomers at the Yerkes Observatory did not realize it.