Dearborn Observatory

The Dearborn Observatory is an astronomical observatory located on the Evanston campus of Northwestern University. The observatory was originally constructed in 1888, through an agreement between the university and the Chicago Astronomical Society. In the summer of 1939, Dearborn Observatory had to be moved to make way for the construction of the Technological Institute. The 1888 observatory is the second Dearborn Observatory, the first had been erected on the Old University of Chicago campus. The observatory is home to the Dearborn 18 1/2 inch refractor, which was the largest telescope in the United States in the late 1860s. Due to the complicated history, it was operated from a different site at that time, and the original tube and mounting is at the Adler Planetarium since 1929. The 18 1/2 was used to discover Sirius B, a companion to the brightest star in the night sky.