The University of Illinois Astronomical Observatory, located at 901 S. Mathews Avenue in Urbana, Illinois, on the campus of the University of Illinois Urbana–Champaign, was built in 1896, and was designed by Charles A. Gunn. It was listed on the National Register of Historic Places on November 6, 1986, and on December 20, 1989, was designated a National Historic Landmark.University of Illinois Astronomical Observatory , NHL Database, National Historic Landmarks Program. Retrieved April 28, 2007.
Though none of the astronomical instruments are being used for professional research today, the observatory still contains a 12" Brashear refractor. The observatory played a key role in the development of astronomy as it was home to a key innovation in the area of astronomical photometry. The facility has been directed by such noted scientists as Joel Stebbins and Robert Horace Baker.University of Illinois Observatory Building -- A Virtual Tour , University of Illinois Astronomy Department, October 2, 2000, University of Illinois. Retrieved April 28, 2007
Erected at the behest of the Illinois General Assembly, the University of Illinois Observatory became important in the development of astronomy due, in large part, to pioneering research by Dr. Stebbins, from 1907 to 1922. Joel Stebbins left the University of Illinois in 1922 but left behind a legacy of discovery that helped alter the face of modern astronomy. The building served the University of Illinois astronomy department from its opening until 1979, when the department moved into a new, larger building to house its growing staff.
History
Early history Astronomy classes at the University of Illinois date to its earliest days. The first courses focused on measurement of the night sky and was taken by civil engineering students to sharpen their surveying skills. A small observatory consisting of a 4-inch refractor and a small transit telescope was constructed by 1872. The astronomy courses were typically taught by the mathematics department and by the early 1890s, several mathematics instructors wanted to do more with astronomy. An expanded astronomy curriculum would require a new larger facility.
The Illinois state legislature voted in 1895 to fund a new teaching observatory at the University of Illinois, providing $15,000 for construction. The site chosen was a grass knoll between Matthews Avenue and Burrill Avenue, just north of the Morrow Plots, a National Historic Landmark that is the nation's oldest experimental field. Contracts were extended to Charles A. Gunn, the architect and an instructor on campus, and Bevis and Company in Urbana as the general contractor with construction beginning in April 1896.University of Illinois Observatory , Astronomy and Astrophysics, November 5, 2001, Online Books, National Park Service. Retrieved April 28, 2007 The building was completed by August at a total cost of $6,800. The principle telescope was installed in November and the final telescope was in place by February 1897.
The first director of the observatory was George W. Myers. Myers was a Champaign county native who graduated from the university in 1888. He remained as a mathematics instructor also teaching the spring Descriptive Astronomy course. In preparation for the directorship he spent two years in Munich earning his Ph.D. in astronomy. In his first year as director, G.W. Myers announced the discovery of the source of the variability in the star Beta Lyrae at the opening conference for Yerkes Observatory. He served as director from 1897 until 1900 when he left for the University of Chicago.History of the University of Illinois Observatory, University of Illinois Astronomy Department, 2012. University of Illinois. Retrieved April 28, 2007 W.C. Brenke, an astronomy instructor, served as acting director until a new director was hired in 1903.
Stebbins' research Before 1907, all magnitude measurements for stars were obtained through visual comparison of relative brightness, a process that was slow and inexact. Later photographic methods would use starlight to make a representation on a photographic plate. Regardless, neither method was adequate for quantitative measurements. The drawback of previous methods of measuring stellar magnitude made the use of electricity for empirically gathering astronomical data revolutionary for the science of astronomy. Joel Stebbins' pioneering research for astronomical photometry took place at the observatory.
Stebbins arrived as director of the University of Illinois Observatory after he completed his Ph.D. at the University of California, Berkeley in 1903. Once Stebbins arrived fresh from his dissertation completed at Lick Observatory, he began a two-year study of the brightness of 107 binary stars using a Pickering visual photometer. The research, with the assistance of his wife, May Stebbins, investigated the relative brightness on binary stars using visual techniques. In a 1957 speech at the American Astronomical Society, Stebbins recalled the events which led to the electric cells:
She [May Stebbins] wrote down the numbers as the observer called them, but after some nights of recording a hundred readings just to get one magnitude, she said it was pretty slow business. I responded that someday we would do all this by electricity. That was a fatal remark. Thereafter she would often prod me with the question, "When are you going to change to electricity?" It happened that within two or three months, the Department of Physics gave an open house, and one of the exhibits was in [the] charge of a young instructor, F.C. Brown. He showed how, when he turned on a lamp to illuminate a selenium cell, a bell would ring, when the lamp was off, the bell would stop. Here was the idea: Why not turn on a star to a cell on a telescope and measure a current?
Stebbins and Fay C. Brown soon became friends and in time, they had a selenium cell positioned on the telescope at the observatory. In the summer of 1907, after several attempts, the two achieved a light curve for Earth's moon and measured the moon's brightness during a lunar eclipse. This marked the first time in America that electricity was used to measure astronomical brightness. Later Stebbins went further, discovering that by cooling the cell to zero degrees Fahrenheit he would double the cell sensitivity and diminish irregularities in the circuit tenfold, still further, by reducing the size of the cell the irregularities were reduced more. The pair went on to detect stellar intensity and activity that were previously unrecorded. In 1909 their observations of Algol detected for the first time the second minimum as well as limb brightening. The coming of Comet Halley in 1910 allowed Stebbins, in May, to use his selenium photometer to study the comet. Two years later Stebbins used the photometer and discovered four stars to be eclipsing binary stars: Beta Aurigae, Spica, Alpha Coronae Borealis and Delta Orionis.
Although the selenium cell photometer was proving successful, it was difficult to use and not very sensitive. Illinois physics professor Jakob Kunz suggested that Stebbins try a photoelectric cell. Kunz had been experimenting on an improved photoelectric cell which was alkali based. Kunz's cell was the predecessor of the modern day "electric eye." Stebbins left for a sabbatical in Europe in fall of 1912. While he was gone, Kunz and another Illinois physicist, W.F. Schulz, successfully tested a photoelectric cell photometer at the observatory.
Upon his return from sabbatical in August 1913, Stebbins ended his pioneering work with the selenium cell and began working with Kunz on the new photometer.
In 1915, Stebbins' object of study became the star involved in Myers' first big discovery at the observatory, Beta Lyrae. He thus began an aggressive research program that produced a series of papers in the Astrophysical Journal on eclipsing binaries Lambda Tauri, Algol, 1H Cassiopeiae (HR 8926), ellipsoidal variables π5 Orionis, and b Persei, and Nova Aquilae (V603 Aquilae) in 1918. Stebbins and Kunz also travelled to Wyoming to study the Solar eclipse of June 8, 1918. Dr. Elmer Dershem joined the observatory staff in 1917 and rebuilt the photometer in the summer of 1919. By 1922, Charles Wylie completed the first Illinois astronomy doctorate for his photoelectric studies of the Cepheid Η Aquilae, and Sigma Aquilae noting its variations due to tidal distortions.
In 1913, Stebbins was awarded the Rumford Prize of the American Academy of Arts and Science, and in 1915 the Henry Draper Medal of the National Academy of Sciences. The research was also supported by grants from the Draper fund of the National Academy of Sciences and the Rumford Fund of the American Academy of Arts and Sciences. Stebbins served as an officer of the American Astronomical Society and was one of the American delegates in 1918 to attend the organizational meeting of the International Astronomical Union in Brussels.
Stebbins left the University of Illinois in 1922 for the Washburn Observatory in Wisconsin and Dr. Robert H. Baker took over as the new Director of the University of Illinois Observatory. However, discovery and science did continue at the university's observatory.
Robert Baker, third director
When Robert Baker arrived he continued a photoelectric photometry program focusing on variable stars. He continued to use the 12-inch refractor until 1927 when a new photometer was constructed and attached to the 30-inch reflector telescope in the observatory annex.The many transformations of the University of Illinois annex, Svec, Michael, 21 (1) 81-93, 2018 Journal of Astronomical History and Heritage. Retrieved May 2018 He supervised two graduate students who worked on this equipment in the early 1930s. On May 27, 1933, the star Arcturus provided light which fell onto a photo cell in the observatory's annex and sent a signal to open the Chicago World's Fair.
The Great Depression was soon in full swing and the department budget fell from $1000 to $200. It was during this time that Dr. Baker authored a number of books. In 1930, he authored the textbook Astronomy, followed in 1932 by The Universe Unfolding, and his revision of Simon Newcomb's Astronomy for Everyone. In 1934 Baker described an imaginary trip to the moon in When the Stars Come Out. His second textbook, An Introduction to Astronomy also appeared in 1934. Introducing the Constellation was published in 1937 and, with the help of Howard Zim in 1951, Stars: A Guide to the Heavens. His textbooks were used across the country for undergraduate astronomy courses and praised as classics.
After two sabbaticals to Harvard, Baker's interest moved from photometry to the Milky Way. In 1939 the 30-inch reflector was replaced with a Ross photographic telescope and in the years 1939 through 1951, Baker used the observatory's photographic telescope to help count the stars in the Milky Way and determine their distribution as part of Harvard University's Star Counting Circuit. This would be the primary research until Baker's retirement in 1951. The 12-inch refractor was only used for instruction, public open houses and for visiting school groups.
Modern department