University of Illinois Observatory

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University of Illinois Astronomical Observatory
(National Register of Historic Places)
The observatory at U of I is a National Historic Landmark.
The observatory at U of I is a National Historic Landmark.
Location: Urbana, Illinois, Champaign County, Illinois, USA
Coordinates: 40°6′35″N, 88°12′15″W
Built/Founded: 1896
Added to NRHP: November 6, 1986[1]
Governing body: University of Illinois

The University of Illinois Astronomical Observatory was constructed in 1896. It stands at 901 S. Matthews Ave. in Urbana, Champaign County, Illinois. The observatory is listed on the National Register of Historic Places, a status it gained on November 6, 1986. On December 20, 1989 the U.S. Department of Interior declared the U of I Observatory a National Historic Landmark.[1] Though none of the astronomical instruments are being used for 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.[2]

Contents

[edit] 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, a grassy knoll betweens Mathews 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 and older and smaller observatory formerly located 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.[3]

The observatory was built on a one story T plan, facing north, of buff-colored Roman brick (from Indiana) with limestone lintels and sills. The bar of the T is 75 feet long east to west and 25 feet deep, its stem is located to teh south, centered along the east-west axis and is 26 feet deep by 25 feet wide. The octagonal observation tower rises 25 feet into the air at the intersection of the T when it becomes round and continues to a height of 35 feet. 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, it carries the dome track. Internally, the diameter of the dome is 24.5 feet and its zenith 24 feet above the floor. The slit, which still operates, has an opening of 44 inches 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.[3]

The 12-inch refractor telescope in the equitorial room of the U of I Observatory.
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The 12-inch refractor telescope in the equitorial room of the U of I Observatory.

In the center of the equatorial room is the 1896 12 inch refractor telescope. Built by the firm of Warner and Swasey, Cleveland, Ohio, the scope is stablized 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 its original observer's chair which was mentioned in the original contract with Bevis and Company of Urbana at a cost of $25. The entrance hall below the equatorial room, octagonal in shape, is centered around a brick pier. The original stairs, newel posts, balustrades and wood floors are still in place and the room is used for its original purpose, storage.[3]

In the original observatory there were two transit rooms in the east and west wings. 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.[3]

The exterior of the observatory building is 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 transome and concrete stoop. The original front balustrade has been replaced the western stoop and ornamental iron balustrade is still original.[3]

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 addition 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 addition also included space for a new darkroom and a radio telescope laboratory. [3]

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.[2]

[edit] Astronomical significance

The observatory holds significance is 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 Warner and Swasey refractor telescope in the second stroy 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 became standard technique.[3]

[edit] Stebbins' research

Stebbins' photoelectric photometer mounted on the 12-inch refractor in 1913.
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Stebbins' photoelectric photometer mounted on the 12-inch refractor in 1913.

Before 1907 all magnitude measurements for stars were obtained through visual comparison of relative brightness, a process that was slow and in exact. Later, after 1907 photographic methods would use starlight to make a representation on a photographic plate. Regardless, neither method was adequate for quantitative measurements. Because of the drawbacks of methods for finding stellar magnitude being use, the use of electricity for empirically gathering astronomical data was revolutionary for the science of astronomy. Joel Stebbins' pioneering research for astronomical photometry took place at the observatory.[3]

Stebbins arrived as director of the University of Illinois Observatory after he completed his Ph.D. at the University of California, Berkeley in 1903. Stebbins' research took place over the years of 1907 to 1922 and investigative 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:[3]

"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 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?"[3]

The selenium cell photometer mounted on the refractor telescope at the U of I Observatory in 1910.
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The selenium cell photometer mounted on the refractor telescope at the U of I Observatory in 1910.

Stebbins and Brown soon became friends and in time they had a selenium cell positioned on the 12 inch 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.[3]

Stebbins pioneering work with the selenium cell continued until 1913 when he and University of Illinois physics professor Jacob 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." [3]

[edit] Other discoveries

A number of other notable astronomical discoveries occurred at the observatory through the years. The first director of the obervatory 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.[4]

  • 1897: Director G.W. Myers annouced the discovery of the source of the variability in the star Beta Lyrae.[4]

Once Stebbin's 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.[4]

  • 1907: Stebbins and F.C. Brown use the selenium cells to study the brightness of the Moon. This marks the first time in America that electricity is used to measure astronomical brightness.[4]
  • 1910: In May Stebbins useds the selenium photometer to study Comet Halley. [4]
  • 1915: The star Beta Lyrae becomes Stebbins' object of study.[4]
  • 1918: On June 9 Stebbins and physicist Jakob Kunz observe the solar eclipse from Wyoming using the photometer[4]

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. Simply because the observatory lost its pioneering researcher in Stebbins did not mean that discovery and science did not continue at the university's observatory.[4]

  • 1933: On May 27 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.[4]
  • 1939-1951: Baker used the obervatory's photographic telescope to help count the stars in the Milky Way and determine their distribution. This was part of the Harvards' Star Counting Circuit.[4]

[edit] Further reading

  • Francissen, Shauna J. "National Register of Historic Places Inventory-Nomination Form-University of Illinois Astronomical Observatory." Urbana, Illinois: Preservation and Conservation Association, 1986.
  • Myers, G.W. "The Astronomical Observatory at the University of Illinois." Popular Astronomy, 6 (1898).
  • Stebbins, Joel. "Jacob Kunz, 1874-1938," Popular Astronomy, March 1939.
  • Stebbins, Joel. The Brightness of Halley's Comet as Measured With a Selenium Photometer," Astrophysical Journal, July 1910.
  • Stebbins, Joel. "The Washburn Observatory," Publications of the Astronomical Society of the Pacific, Vol. 70, No. 416, p.437, 1958.
  • Struve, Otto, and Velta Zebergs. Astronomy of the Twentieth Century. New York: Macmillan, 1962.
  • Svec, Michael T. The University of Illinois Astronomical Observatory. Urbana, Illinois: 1988.
  • University of Illinois Archives, Observatory file, Urbana, Illinois. Warner and Swasey. A Few Astronomical Instruments. Cleveland, 1900.
  • Whitford, A.E. '"American Pioneer in Photoelectric Photometry,"' Sky and Telescope, May 1966.

[edit] Notes

  1. ^ a b NRIS Database, National Register of Historic Places, retrieved Oct. 2006.
  2. ^ a b University of Illinois Observatory, University of Illinois.
  3. ^ a b c d e f g h i j k l University of Illinois Observatory, Astronomy and Astrophysics, National Park Service.
  4. ^ a b c d e f g h i j k History of the University of Illinois Observatory and 12" Refractor, University of Illinois.
  5. ^ Aeronautical and Astronautical Events of July-September 1961, July 1961, NASA.
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