University of Illinois Observatory

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University of Illinois Observatory
The University of Illinois Astronomical Observatory was constructed in 1896. It stands on South Matthews Avenue in Urbana, Champaign County, Illinois. The observatory was listed on the National Register of Historic Places on November 6, 1986 and on December 20, 1989, the U.S. Department of Interior designated the observatory a National Historic Landmark. 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 H. Baker. Erected in 1896 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 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, itself, is in a traditional observatory design, following a T-plan. The dome rises 35 feet (11 m) in the air. 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.


Early history
The Illinois state legislature voted in 1895 to fund a new observatory at the University of Illinois, the legislation provided $15,000 to build the building. The site chosen was a grass knoll between Matthews Avenue and Burrill Avenue, just north of the 1876 Morrow Plots, a National Historic Landmark that is the nation's oldest experimental field. The building was constructed to replace an older and smaller observatory on campus. Contracts were extended to Charles A. Gunn, the architect, and Bevis and Company in Urbana as the general contractor in the spring of 1896 and construction began in April. The building was completed by August at a total cost of $6,800.

Astronomical history
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, after 1907, 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. His key research took place between the years 1907 and 1922. The research, with the assistance of his wife, May Stebbins, investigated the relative brightness on binary stars using visual and photographic techniques. In a 1957 speech at the American Astronomical Society, Stebbins recalled the events which led up 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 Brown soon became friends and in time, they had a selenium cell positioned on the 12-inch (300 mm) telescope at the observatory. In the fall of 1907, after several attempts, the two achieved a light curve for Earth's moon. Their successful use of photoelectric technology was a huge leap for astronomers. 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. Stebbins pioneering work with the selenium cell continued until 1913, when he and University of Illinois physics professor JaKob Kunz became associated. Kunz had been doing experimentation on an improved photoelectric cell which was alkali based. Kunz's cell was the predecessor of the modern day " electric eye." Other discoveries A number of other notable astronomical discoveries occurred at the observatory through the years. The first director of the observatory was G.W. Myers; however he left the University of Illinois in favor of the University of Chicago. He served as director from 1897 until 1900. In his first year as director, G.W. Myers announced the discovery of the source of the variability in the star Beta Lyrae. Once Stebbins arrived, in 1903, from Lick Observatory, he began to study the brightness of 107 binary stars. By 1907 when Stebbins and Brown used the selenium cells to observe the brightness of the moon, including a July Lunar Eclipse, discoveries of mammoth astronomical proportions began to become commonplace at the observatory. In 1907 Stebbins and F.C. Brown used the selenium cells to study the brightness of the Moon. This marked the first time in America that electricity was used to measure astronomical brightness. 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. In 1915 Stebbins' object of study became the star involved in Myers' first big discovery at the observatory, Beta Lyrae. A solar eclipse on June 9, 1918 gave Stebbins and physicist Jakob Kunz the chance to observe from Wyoming using the photometer. After numerous discoveries, Stebbins left the University of Illinois in 1922, the same year that Charles Wylie earned the first U of I doctorate in astronomy. Stebbins left for the Washburn Observatory in Wisconsin and Dr. Robert H. Baker took over as the new Director of the University of Illinois Observatory. However, because the observatory lost its pioneering researcher in Stebbins did not mean that discovery and science did not continue at the university's observatory. From 1933 into the 1960s, the observatory at U of I played a role in American astronomy and aerospace history. 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. Budget cuts, a mere $200 per year at this point, would soon follow as the Great Depression was in full swing. For more than ten years after that, 1939 through 1951 Baker used the observatory's photographic telescope to help count the stars in the Milky Way and determine their distribution. This was part of the Harvard's Star Counting Circuit. In 1961, as the Space Race heated up, Senator Paul H. Douglas requested that the membership of the American Astronautical Society be polled by the University of Illinois Observatory as to the "scientific value" of the U.S. plan to land on and return one or more men from the Moon.

Later history
The observatory underwent major renovations and additions in 1956 and 1966, (see architecture section below). In 1967, the 12 inch telescope at the observatory made its last professional photometric observations. The University of Illinois' Astronomy Department moved out of the building in 1979. The same year the observatory received recognition by the National Register of Historic Places, 1986, thousands gathered at the site to observe Comet Halley's journey into the inner solar system. The observatory is no longer used for research purposes, though the telescope is still used as a teaching tool in the university's astronomy classes. In addition, a University of Illinois student astronomy organization uses the telescope. The observatory dome underwent a renovation that included repainting in 1996.

The observatory was built on a one story T-plan, facing north, of buff-colored Roman brick (from Indiana) and features limestone lintels and sills. The cross of the T is 75 feet (23 m) long east to west and 25 feet (7.6 m) deep, its stem is located to the south, centered along the east-west axis and is 26 feet (7.9 m) deep by 25 feet (7.6 m) wide. The octagonal observation tower rises 25 feet (7.6 m) into the air at the intersection of the T where it becomes a dome and continues to a height of 35 feet (11 m). At floor level of the second equatorial room a balustrade circles around the exterior of the tower. The tower is capped by a great circular limestone plate, which carries the dome track. Internally, the diameter of the dome is 24.5 feet (7.5 m) and its zenith 24 feet (7.3 m) above the floor. The dome slit, which still operates, has an opening of 44 inches (1,100 mm) and can be opened or closed by hand in seconds. The dome tower and equatorial room are original save a motor drive which replaced the old rope and sheave method of rotating the dome. In the center of the equatorial room is the 1896 12-inch (300 mm) refractor telescope. Built by the firm of Warner and Swasey, Cleveland, Ohio, the scope is stabilized on a brick pier which extends down into the bedrock and is not attached to the building in any way. The telescope cost $4,500 and still has the original observer's chair mentioned in the contract with Bevis and Company at a cost of $25. The entrance hall, below the equatorial room, octagonal in shape, is centered around a brick pier. The entrance hall retains original stairs, newel posts, balustrades, and wood floors; it is still used for its original purpose, storage. The east and west wings of the building once each contained a transit room. Each of the rooms had a mounted transit telescope on a brick pier; the piers are still visible in the basement below the transit rooms. The transit rooms themselves have since been converted into office space. The exterior of the observatory building has a brick cornice, with stone sills and lintels, stone water course, ornamental gutters, and original copper downspouts. Most of the building's windows are of the wooden double-hung variety and original, as are the front entrance door transom and concrete stoop. The original front balustrade has been replaced, however, the western stoop and ornamental iron balustrade is still original. Aside from the transit room conversion to office space the building has seen other major work in the past. The southwest corner of the building was built in 1956, of cream colored brick, to house additional classrooms and office space. The addition of 1956 took special care to replicate nearly every aspect of the original building except for color. Another major addition occurred in 1966 with the construction of the large east wing. Of the same cream colored brick as the 1956 addition, it also tried to mimic the building's finer details. The 1966 east wing addition provided for, again, more office space, but this project also included space for a new darkroom and a radio telescope laboratory. The observatory basement and the dome housing the refractor are still in use by the astronomy department at U of I and the University of Illinois Astronomical Society, a student organization on campus.

Historic significance
The observatory holds significance in astronomy because of its association with the development of selenium photoelectric cell. The cell revolutionized the science of astronomical photoelectric photometry. This branch of astronomy measures stellar magnitude. The research regarding photometry was conducted on a 12-inch (300 mm) Warner and Swasey refractor telescope in the second-story equatorial room. The selenium cell was developed by Joel Stebbins from 1907 to 1922 while he directed the observatory. As a result of Stebbins' work determining stellar magnitude using photoelectric photometry, it became standard technique. Due to this astronomical importance the observatory was listed on the National Register of Historic Places on November 6, 1986 and on December 20, 1989 the U.S. Department of Interior designated the U of I Observatory a National Historic Landmark.

Building Activity

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