Central telescope pier

The Observatory’s larger of two telescopes stands on a central pier, designed to minimize vibrations. The pier, constructed of solid brick masonry, is submerged 15 feet below grade, rises to the dome 40 feet above ground level, and is 20 feet in diameter at its base. It is isolated from the ground and dome floors by a 1-inch gap.

Dome rotation

The Observatory dome originally ran on five cannonballs that rolled freely in a circular groove. Because nothing maintained the distance between the cannonballs, they would eventually clump together toward one side, making rotation impossible. When this happened, timbers were inserted into slots in the dome, the dome was “jacked up,” and the cannonballs redistributed. In 1890, the system was replaced with railroad-style wheels running on a track, as can be seen today.

Mary E. Byrd

Mary Byrd graduated from the University of Michigan in 1878. Although she did not study at the Observatory, she went on to become a prominent astronomer and a pioneer in astronomy education. For nearly twenty years, Byrd directed the observatory at Smith College. In this same time period, she published two widely used astronomy textbooks. In protest of the institution’s acceptance of donations from Andrew Carnegie and John D. Rockefeller, she resigned from Smith College in 1907.

Fitz lens cell

The Fitz refractor’s objective lens (the lens at the large end of the telescope) is known as a doublet achromatic lens. It consists of two lenses, one concave and one convex. This combination of lenses helps to reduce the image distortions caused by the fact that light of different colors come into focus at different points; the concave lens corrects for these distortions made by the convex lens.

Director’s Residence

In 1868, a residence for the director and his family was built to the east of the Observatory. The residence was enlarged and updated in 1905. Beginning with James Craig Watson, seven directors and their families lived in the residence. In 1942, it became a residence for women students, in 1946, it was converted to apartments for faculty, and in 1954 it was torn down to make room for the expansion of Couzens Hall.

Moons of Mars

On August 12, 1877, Asaph Hall, Sr., an alumnus of the Detroit Observatory, discovered a moon of Mars known as Deimos while working at the US Naval Observatory in Washington, D.C. Six days later, he discovered Mars’s second moon, Phobos. Before going on to become one of the nation’s leading astronomers, Hall had trained at the Detroit Observatory under Franz Brünnow.

Before Apollo

This image of the moon is from 1932, taken by amateur astronomers Charles and Robert McMath, who were formally affiliated with the University’s Observatory. Their movie of the moon was produced for public use by British Pathé Pictures, who claimed, “The moon appears exactly as it would were you speeding through space at 1,000 miles a minute – 300 miles above its airless and lifeless surface.” This movie, which can be found at https://youtu.be/PwGm4mIxiPg, helped the public understand the dynamic atmosphere of the sun.