2019 cistern discovery

In 2019, construction crews excavating for the Observatory’s addition discovered a forgotten cistern on the south side of the building. The cistern — 10 feet in diameter and 12 feet deep — contained 4000 gallons of water that had to be pumped out and trucked off site. The construction date of the cistern and what was connected to it remain unknown.

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.

Watson’s discovery of Juewa

On October 10, 1874, James Craig Watson, while on expedition in China, discovered an asteroid — his 16th. Although asteroids were traditionally named for figures from Ancient Greek mythology, Watson asked his Chinese hosts to provide the name. They chose “Juewa” (瑞華星 ), or, “Star of China’s Fortune.” 139 Juewa was the first asteroid discovered in China.

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.

Student transit I

In 1878, a small observatory was constructed 100 feet southeast of the Detroit Observatory, in anticipation of observing the transit of Mercury across the Sun, which occurred on May 8 of that year. This observatory was responsive to a program of the federal government to observe the transit and was temporarily made a U.S. Government Station.

Schaeberle comet discovery

On July 14, 1881, Observatory astronomer J. Martin Schaeberle discovered his second comet. A student described it thus: “With another woman student I had been working under Mr. Schaeberle’s supervision … until the wee hours of the night … Presently, [Schaeberele] hurried into the observatory and asked to use the telescope. We found that he had seen a comet …”

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.