Milestone Moments

The Detroit Observatory was built in 1854 and quickly became a center of scientific advancement, helping realize Henry Tappan’s vision of creating the first true American research university. Read about significant milestones in its long history as the Observatory and its researchers rose to prominence.

“the place to study astronomy …”

From the 1850s to the 1880s, the U-M Detroit Observatory was widely viewed as one of the two or three leading observatories in the United States.  As alumnus Cleveland Abbe later recalled, when as a young man he wrote to astronomers across the country to ask where he should study, there was a clear verdict: Ann Arbor.

Pioneering the American Research University

Michigan’s first president, Henry Philip Tappan, was a higher education visionary who helped create the modern research university, where “those who would advance human knowledge, may want nothing that can aid them.”  He began by building the Detroit Observatory.

“The Ann Arbor School of Astronomy”

The Observatory’s first director, Franz Brünnow, brought precision astronomy education and new standards for research to the United States, making the Detroit Observatory a training ground for many of the leading American astronomers of the 1800s.

“Bagging asteroids”… and building the model of the solar system

James Craig Watson’s discovery of nearly two dozen asteroids, his rigorous observations of eclipses and transits, and his pursuit of a hidden planet, helped form the map of the solar system, made him a national celebrity, and generated tremendous public support for astronomy.

Populating American Science

Astronomers who studied and worked at the Detroit Observatory fanned out across the country, founding, directing, and staffing leading observatories — from the Lick Observatory in California, the premier U.S. observatory at the end of the 19th century, to the Smith College observatory, a center for education of women in astronomy.

Time After Time

Before time zones, astronomers at the Observatory used positions of the stars to set the standard time for businesses, the railroads, and citizens in the state of Michigan, moving beyond an era where every community had its own time — or several times.

Mapping the Continent

Astronomers from the Observatory played key roles in the national effort to survey the continent for purposes of science, navigation, and westward expansion and land management.  The U.S. Geodetic, Geological, Coastal, Lakes and Western States Surveys took U-M astronomers from the tip of Florida to the far reaches of Alaska.

"We were rather an earnest and self reliant group."

So recalled Mary Byrd, the first woman from U-M to become an astronomer, speaking of her female cohort at Michigan in the 1870s.  Women students “were unwelcome,” she said, but the “professors themselves … were always courteous and considerate.”  Byrd authored two important astronomy textbooks and taught astronomy at Smith College for many years — where she was succeeded by Harriet Williams Bigelow, the first woman Ph.D. astronomer from U-M.

Inventing Meteorology

Observatory alumnus Cleveland Abbe developed numerous innovations to weather forecasting.  His work led to the creation of the  National Weather Bureau, whose first director was Mark Harrington, an Observatory alumnus and its third director. Abbe later also penned the report that led to the creation of standard time zones.

Comets, the Sun, and the Moons of Mars

Astronomers working at or trained at the Detroit Observatory contributed numerous discoveries to the growing stock of astronomical knowledge in the 19th century, helping to revolutionize understanding of the solar system.  Among the discoveries were Watson’s 22 asteroids, several comets, the moons of Mars, and critical features of solar eclipses.

The 1857 Fitz Refracting Telescope

In 1857, the Detroit Observatory installed the third-largest refracting telescope in the world. That a new observatory in the American Midwest would be the home of such a cutting-edge instrument is a testimony to the University’s groundbreaking commitment to astronomical research, under the leadership of President Henry Philip Tappan.

The 1857 Fitz Refracting Telescope

The telescope was manufactured by Henry Fitz, America’s first great telescope maker. When an approved telescope was finally installed in 1857, Professor Brünnow immediately put it to good use. The 12-5/8” objective diameter, 17-foot-focal-length telescope became part of a research program dedicated to rigorous investigation of asteroids, double and variable stars, and planets — all critical research efforts in mid-19th-century astronomy. More than 20 asteroids and three comets were discovered using the Fitz refractor, and it was applied to detailed mapping of the planet Mars and other phenomena.

The 1857 Fitz Refracting Telescope

The Fitz refractor sits atop a limestone pier weighing four tons, which rests on a 60-foot brick masonry pillar that extends 15 feet below grade. In its original configuration, the Fitz refractor had a pine wood tube and equatorial mount that allowed it to track celestial movements. As astrophotography developed in the late 1800s, the wood tube was replaced with the more rigid steel tube that you can see today. A new equatorial mount and clock drive were also installed at that time. Interestingly, Henry Fitz’s 1857 objective lens was not reconfigured then or since. Consequently, it is the only Fitz lens in its original condition, making it of great historical interest.

The Meridian Circle Telescope

Think of today’s technologically advanced means for determining time and location, such as cesium clocks and the GPS satellite network.  The Meridian Circle Telescope (MCT) was the 1800s equivalent.

The MCT was designed for one scientific function with two purposes. Its function was measuring the position of stars and other celestial bodies with extreme precision. And, because the precise position of a star is determined by two coordinates—its “declination,” i.e., its north-south position, and its “right ascension,” which is determined by the hour-minute-second at which it crosses the meridian—its position can also be used to set exact time. So, the MCT was a celestial-positioning tool and a time-setting tool of tremendous accuracy.

The Meridian Circle Telescope

The MCT is named for Henry Nelson Walker, the Detroit financier who, in 1852, helped Henry Tappan solicit funds to create the Observatory. Walker was interested in the telescope because of its time-setting capacity as well as its research importance. The telescope was manufactured by the German firm Pistor & Martins in 1854. It was so impressive that Franz Brünnow, who oversaw its production, said “any astronomer would be lucky to use it.”

The Meridian Circle Telescope

In addition to mapping stars, asteroids, and comets, the MCT was used to set time for Detroit businesses, the Michigan Central Railroad, and railroad stations throughout the state. Eventually, standard time zones—as proposed by Detroit Observatory alumnus Cleveland Abbe—would eliminate the need for regional observatories to set the time.

Detroit Observatory Historical Timeline

  • 1852

    Henry Philip Tappan becomes U-M's first president in Ann Arbor, collaborates with Henry Walker of Detroit to raise funds for an observatory.


  • 1853

    Construction of Observatory begins.

  • 1853

    Tappan orders a 12.5" refracting telescope from Henry Fitz of New York.

  • 1853

    Tappan meets astronomers Johann Encke and Franz Brünnow at the Royal Observatory in Berlin. Brünnow agrees to oversee manufacture of a meridian circle telescope on Tappan's behalf.

  • 1853

    Tappan orders a 6" meridian circle telescope from the firm of Pistor & Martins of Berlin.

  • 1854

    Franz Brünnow is appointed first Observatory director.

  • 1854

    Observatory building is completed.

  • 1854

    Meridian circle telescope and Tiede sidereal clock are installed.

  • 1855

    Jasper Cropsey, Hudson River painter, visits campus at Tappan's invitation and paints the Observatory and a campus landscape.

  • 1857

    Following delivery of a defective Fitz telescope and use of a telescope on loan, the new Fitz refracting telescope — the current one — is installed in the dome.

  • 1857

    Franz Brünnow and Rebecca Tappan marry.

  • 1857

    James Craig Watson, Brünnow's star student, graduates.

  • 1858

    Brünnow begins publication of 'Astronomical Notices,' U-M's first scholarly publication.

  • 1859

    Brünnow accepts appointment at the Dudley Observatory in Albany, NY. James Craig Watson becomes acting director.

  • 1860

    Brünnow returns to the University of Michigan, at the request of the Regents.

  • 1860

    Franz Brünnow publishes his English translation of Part 1 of his magnum opus, Lehrbuch der spärischen Astronomie (Handbook of Spherical Astronomy). It will be a widely-used astronomy text for decades to come.

  • 1861

    Longitude of Detroit Observatory is established, via telegraphic connection and joint observations with Hamilton College observatory.

  • Fauth Chronograph Detail - cylinder and pen


    Observatory time service begins this year.

  • 1863

    Tappan is dismissed by Regents; Brünnow resigns; James Craig Watson becomes Observatory's second director.

  • 1863

    Watson discovers his first asteroid, 79 Eurynome. Over the next 15 years, he will discover 21 more — out of 100 discovered worldwide during that period.

  • 1865

    Brünnow is appointed Astronomer Royal at the Dunsink Observatory in Ireland.

  • 1867

    Watson discovers asteroids 93 Minerva and 94 Aurora.

  • 1868

    A director's residence is added to the west side of the Observatory, connected via the director's office in the west wing. City of Ann Arbor improves roads around the Observatory.

  • 1868

    Watson discovers an unprecedented six asteroids: 100 Hekate, 101 Helena, 103 Hera, 104 Klymene, 105 Artemis, 106 Dione.

  • 1869

    Watson observes total solar eclipse in Iowa

  • 1870

    Watson works on Washington Zone astronomical observations for the U.S. Coastal Survey and also observes a solar eclipse in Sicily.

  • 1871

    Watson discovers 115 Thyra.

  • 1872

    Watson discovers 119 Althaea, 121 Hermione, 128 Nemesis.

  • 1873

    Watson discovers 132 Aethra, 133 Cyrene.

  • 1874

    Watson, in China for the transit of Venus, discovers 139 Juewa, allowing his Chinese hosts to name it. It is reportedly the first asteroid discovery in China.

  • 1875

    Watson discovers 150 Nuwa.


  • 1876

    Watson discovers 161 Athor and 168 Sibylla .

  • Watson Andromache discovery dispatch


    Watson discovers 174 Phaedra, 175 Andromache, and 179 Klytaemnestra, concluding his remarkable run of discoveries.

  • 1878

    U.S. Government station set up on Observatory grounds to observe transit of Mercury; it then becomes the first Student Observatory.

  • 1878

    Mary Byrd graduates from the University of Michigan. She would go on to become the first director of the Smith College Observatory and inspire generations of future female astronomers, including Harriet Williams Bigelow.

  • 1878

    Watson claims to have discovered Planet Vulcan while observing a total solar eclipse in Wyoming.

  • 1879

    Watson leaves U-M to become director of the new Washburn Observatory at University of Wisconsin-Madison. His student Mark W. Harrington is named director.

  • 1880

    Student observatory is outfitted with new telescopes, including the 3" transit telescope by Fauth & Co with Clark optics, still in the Observatory's collection.

  • 1880

    Assistant director J.M. Schaeberle discovers a comet, 1880 II.

  • Detroit Observatory weather log 1886


    The Observatory's 3rd director, Mark Harrington, begins meterological observations at the Observatory.

  • 1881

    Schaeberle discovers another comet, 1881 IV.

  • 1884

    Harrington founds 'American Meteorological Journal.'

  • 1890

    Dome is converted: new shutter, dome cannon-ball rollers replaced with railroad-style track and wheels.

  • 1891

    Harrington becomes first Chief of the U.S. Weather Bureau.

  • Harriet Bigelow and Charles Ridell adjust telescope for eclipse


    Harriet Williams Bigelow becomes the first woman to receive a Ph.D. in astronomy from Michigan. She goes on to become a leading astronomer until her untimely death in 1934.


  • 1905

    William J. Hussey is appointed director. He begins to rebuild the U-M astronomy program, which had fallen behind the times in the previous two decades.

  • 1907

    Fitz telescope is converted to steel tube; new mount; drive clock added.

  • 1908

    Student Observatory moves to the west side of the Observatory.

  • 1908

    Large 1908 addition is constructed on the east side of the Observatory.

  • 1911

    37-1/2" reflecting telescope is completed and installed in dome of 1908 addition.

  • 1911

    In an effort to ward off encroaching development, the Observatory grounds are expanded to the east by a gift of 26 acres from R.P. Lamont (Eng 1861).

  • 1912

    The series Publications of the Observatory of the University of Michigan is launched.

  • 1912

    The University develops plans to construct a coal-fired power plant to the west of the Observatory. Concerned about the impact of pollution on observing, Hussey explores moving the Observatory to Huddy Hill, about 3/4-mile southeast. The power plant is eventually completed in 1924, but the Observatory never moves.

  • 1925

    A 27-inch refractor, named for R.P. Lamont, is completed and tested at the Observatory. Seeking darker and less polluted skies, Hussey will take the refractor to a new U-M observatory in South Africa. Unfortunately, he dies in transit.


  • 1927

    Student Observatory moves to the roof of Angell Hall.

  • 1927

    Hazel "Doc" Losh joins Astronomy faculty.

  • 1928

    U-M's Lamont-Hussey Observatory in South Africa, with 27-inch refractor, is dedicated.

  • 1930

    Heber Curtis, protagonist in "The Great Debate," named director.

  • 1930

    McMath-Hulbert Observatory is established by amateur astronomers at Lake Angelus, Michigan. Later, a partnership with U-M is formed.

  • 1932

    Robert McMath takes first films of the sun, establishing heliokinematography as a new field of astronomy.

  • 1954

    Director's residence is torn down to make room for Couzens Hall expansion


  • 1965

    The Astronomy Department moves from the Observatory to new quarters in the Dennison Building

  • 1970

    U-M proposes to raze Observatory but Friends of the Observatory are successful in protecting it.

  • 1973

    The Observatory is listed on the National Register of Historic Places

  • 1976

    1908 addition is condemned and razed but the 1854 building is preserved


  • 1994

    Proposal for restoration of the Observatory is developed, and Observatory is transferred to Office of the Vice President for Research.

  • 1997

    Restoration is completed.

  • 2005

    The Observatory is transferred to the Bentley Historical Library.


  • 2009

    Public viewing nights begin.

  • 2018

    Regents approve addition.

  • 2019

    Construction of addition begins.

  • Image of student docent showing young child the Fitz telescope.


    Observatory re-opens with new addition and renamed the Judy and Stanley Frankel Detroit Observatory.

Popular Articles and Videos

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    Architect's rendering of the Detroit Observatory addition

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    Stars Rising: Why the Detroit Observatory Matters

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    A Creation of My Own

    U-M President Henry Phillip Tappan had bold ideas about what it would take to create a modern research university. The Detroit Observatory was the cornerstone of his vision.

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    The Fault in His Stars

    Mark Harrington was a brilliant botanist, meteorologist, and director of the Detroit Observatory. His tragic battle with mental illness would drive him across oceans, to flop houses and sugar plantations, and eventually to an East Coast asylum.

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    Hidden in Plain Sight

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    The Battle for the Heavens

    When U-M decided to build a coal power plant to fuel a growing campus, faculty doing research at the Detroit Observatory waged a desperate fight to keep the skies clear of black smoke.

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    Professor Porta’s Predictions

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Observatory History in Depth

  • The Detroit Observatory and American Astronomy

  • Timekeeping and the Detroit Observatory

  • Transits, Eclipses, and Missing Planets

  • Comets and the Detroit Observatory

  • The California-Michigan Axis: Lick Observatory and the Revitalization of the Detroit Observatory

  • The Detroit Observatory and Meteorology

  • The Detroit Observatory and the History of Telescopes

  • The Donors to the Observatory

  • A creation of his own : Tappan’s Detroit Observatory

  • “Astronomy.” The University of Michigan, An Encyclopedic Survey

  • A detailed chronology of the Detroit Observatory (Whitesell)

  • Publications about the Detroit Observatory

  • Publications by Astronomers at Detroit Observatory

  • Publications by Astronomers after leaving the Detroit Observatory

  • Citations of Work at the Detroit Observatory