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Short Description (ICOMOS-IAU Case Study format):
University of Illinois Observatory, USA


Geographical position 
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901 S. Mathews Avenue
Urbana, Illinois,
United States of America


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Latitude 40° 6′ 18.9″ N, longitude 88° 13′ 34.1″ W, elevation 227m (744 ft).


General description 
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The University of Illinois Astronomical Observatory was constructed with funding from the state of Illinois in 1896 as a teaching facility. The Observatory is significant for its association with the development of selenium cell and photoelectric cell astronomical photometer that was the beginning of a revolution in photometry and astronomical detector technology. The Observatory continues to function as a teaching facility for both the students and citizens of the university and community.


Brief inventory 
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The 0.9-acre site is located at the southeast corner of the University of Illinois’ main campus Quadrangle and consists of the original Observatory buildings and two later additions. The first addition was constructed in 1956 in the southwest corner of the building. A second larger addition was added in 1966 on the east. Both additions are constructed of the same yellow brick and are harmonious with the original building. See Figure 1a for a map circa 1911 and Figure 1b for a map circa 2014. Located on the south border of the site are the Morrow Plots, the oldest experimental agricultural fields in the United States and a US National Historic Landmark.


Fig. 1. Maps of the University of Illinois’ main campus Quadrangle, containing the Observatory site,
(left) from 1911 (University of Illinois Archives) and (right) from 2015 (Map data ©2015 Google)

The original light-colored cream roman brick Observatory building was one-storey with a high basement. Designed by local architect Charles Gunn, the architectural style is Colonial Revival. The form of the building is a T-plan facing north toward the main campus with four transit rooms occupied the east and west wings and a classroom to the south. Rising from the center was a 2-storey octagonal observation tower that contained on the first floor a foyer, clock room and dark room. The second storey contained the equatorial room home to the principal instrument under a 24-foot wooden dome. A wood balustrade surrounds the observation tower. See Figure 2 for the floor plan and Figure 3 for an exterior view from 1897.


Fig. 2. Floor plan of the main Observatory building. From George W. Myers, “The Astronomical Observatory”, The Technograph 11 (1896–97), 104–111, p. 106.
University of Illinois Archives, no. 1521


Fig. 3. Exterior view of the main Observatory building, taken in 1897. From George W. Myers, “The Astronomical Observatory”, The Technograph 11 (1896–97), 104–111, p. 104. University of Illinois Archives, no. 2707


The main instrument is a 12-inch (30.5 cm) Warner and Swasey equatorial refractor with and objective by John Brashear. The telescope retains much of its original character and integrity and has been in continuous use since November of 1896. The telescope was restored in 1954 by the J.W. Fecker Company and again in 2013 by Ray Museum Studios. Auxiliary equipment for this telescope includes the original Warner & Swasey filar micrometer and a plate camera. Additional equipment includes an Alvan Clark & Sons visual polarizing photometer and a Brashear visual spectroscope. The wooden observing chair is original to 1896 and still used. This telescope as well as the polarizing photometer and the spectroscope was significant to the work of Joel Stebbins. Other physical apparatus used by Stebbins include a Weston reflection galvanometer, reading telescope, voltmeters, and Stebbins’s 1913 Rumford Medal.

The Observatory was home to four transit telescopes. The transit rooms have been slowly converted into office space starting in 1922 and ending in 1974. Of the original four instruments, two remain and are on display: a 2-inch Troughton and Sims Universal Telescope and a 3-inch Warner & Swasey Combined Transit and Zenith telescope.

The clock room remains with the original Warner and Swasey drum chronograph, Green’s mercury stick barometer, and brick clock pier. The original clocks by Clemens Riefler are now in the collection of the Adler Planetarium in Chicago. Those clocks were replaced with 2 IBM master clocks in 1954 that are stored in the clock room.

Other significant objects located in the Observatory or in storage at the Astronomy Department include two P & R Wittstock engineer transits, Newton & Company sextant and artificial horizon, Bausch, Lomb & Saegmuller sextant and artificial horizon, Matthew Berge double frame bridge sextant, and 2 Keuffel & Esser sextants. Teaching materials include 35 wooden lantern slides by Newton & Company, framed back and white astronomy prints, framed window transparencies, and several Denover-Geppert celestial globes. Photographs and documentation on the existing collection is available on-line at uiobservatory.omeka.net/


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The University of Illinois Observatory was built in 1896 using a state appropriation of $15,000. The first director was George W. Myers (1864-1931), an exceptional and progressive teacher. A student of Hugo von Seeliger, Myers’ research focused on a detailed theoretical study of the eclipsing binary star Beta Lyrae.

Joel Stebbins (1878–1966) was the second director starting in 1903. Stebbins’ primary research contribution was variables stars and the development of the photoelectric photometer. He also established the Astronomy Department, graduated the first PhD in Astronomy at Illinois, and participated in the American delegation to help rebuild the International Astronomical Union in the aftermath of World War I. His research earned him the American Academy of Arts and Sciences Rumford Prize in 1913 and the National Aademy of Sciences Draper Medal in 1915.

Stebbins left Illinois for the University of Wisconsin in 1922. Robert H. Baker (1883-1964) followed as the next director. During his tenure he made research contributions in the study of variables stars and galactic structure. He enjoyed great success with a series of textbooks and popular astronomy books including The Universe Unfolding (1932), When the Stars Come Out (1934), and Introducing the Constellations (1937).

In 1952 British cosmologist George McVittie arrived as the new chair and built the Astronomy Department into a modern research department. The Observatory served more as office and instructional space for the growing department resulting in the two additions to the building. New programs and facilities were built including the Vermillion River Radio Observatory (1962) and the Prairie Observatory (1967) off campus. By the time of McVittie’s retirement in 1971, the department had grown from one astronomer to nine and had produced 29 masters and 14 doctoral students. The Astronomy Department moved to a new building in 1979. The office space was reassigned to other university departments although the Astronomy Department still retains space for instruction including the clock room and equatorial room.


Cultural and symbolic dimension 
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The Observatory’s historical significance is associated with the development of the selenium cell and photoelectric cell photometer by astronomer Joel Stebbins and Illinois physicists F.C. Brown and Jakob Kunz (1874–1938). Figure 4 illustrates the selenium cell photometer on the Illinois refractor in 1910.

The accurate measurement of the brightness of stars is one of the most fundamental measurements in astronomy and during the 19th century was done primarily by visual or photographic means. Stebbins and his colleagues not only used electrical detectors to improve the precision and accuracy of the measurements, but then proved the quality of the instruments with major discoveries including the discovery of the secondary eclipses of Algol. Stebbins’ work at Illinois (1907–1922) and then Washburn Observatory (after 1922) provided the career-long consistency and success that lead to photoelectric photometry becoming the standard means of astronomical photometry. Of the thirteen American observatories conducting photoelectric photometry before World War II, six had a connection to Stebbins and were employing photoelectric cells made by Jakob Kunz. The photoelectric photometer was not only a revolution in photometry but also marked a shift in astronomical detectors with electrical means eventually replacing photographic films. The way in which astronomers viewed the sky changed as a result of the work started at Illinois.

On the University campus, the Observatory’s design and scale is a clear link to the past history of the campus. Its central location in the heart of the campus provides easy access and visibility. The location of the Observatory next to Morrow Plots, both National Historic Landmarks, speaks to the national significance of research performed at the University.


Fig. 4. The Illinois 12-inch refractor in 1910, with the selenium cell photometer attached. University of Illinois Archives, no. 1629

Fig. 5. The photoelectric photometer in 1915. University of Illinois Archives, no. 5186


Comparative analysis 
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Below is a table listing university observatories at mostly public institutions in the United States. These facilities share a common mission of teaching as well as similar instrumentation and physical size. Their present status including listing on the US National Register of Historic Places (NHR) is identified. The University of Illinois Observatory is unique in that it has achieved National Landmark (NHL) status and that the funding for the building came exclusively from a state appropriation.

Observatory Owner/location Date Equipment Notes Current status
Detroit Observatory University of Michigan, Ann Arbor, MI 1854 12.5-inch Henry Fitz refractor. Building restored in 1998, open for public open houses, NHR*
Washburn Observatory University of Wisconsin, Madison WI 1881 15.6 Alvan Clark refractor, newer mount. Building restored in 2009, telescope still in use for public open houses. NHR*
Ladd Observatory Brown University, Providence RI 1891 Saegmuller mount and 12-inch Brashear optics. Original building, telescope still in active use. NHR*
Dudley Observatory Albany NY March 1894 Warner & Swasey mount M-42, 12-in Brashear optics. Original building torn down in 1965, telescope now in storage at miSci museum in Schenectady NY
Emerson McMillin Observatory Ohio State University, Columbus OH June 1896 Warner & Swasey mount, 12.5-inch Brashear optics. Designed for spectroscopic work. Observatory closed in 1968 and torn down, telescope now in Ballreich Observatory of Heidelberg College, Tiffin OH
University of Illinois Observatory University of Illinois, Urbana IL November 1896 Warner & Swasey mount, M-42, 12-inch f/15 Brashear optics. Original building, telescope restored in 1953 and 2013. NHR*, NHL**.
Kirkwood Observatory Indiana University, Bloomington IN May 1901 Warner & Swasey mount, 12-in f/15 Brashear optics. Original building, telescope still used for instruction, scope and dome renovated in 2002.
Crane Observatory Washburn College, Topeka KS September 1901 Warner & Swasey mount displayed & Paris Exhibition, 11.5-in Brashear, 165-in focal length (f/14). Original building destroyed in 1966 by tornado, telescope restored in 1996, on top of Stoffer Science Hall.
Fuertes Observatory Cornell University, Ithaca NY 1923 Warner & Swasey mount, 12-inch Brashear optics, 4-inch finder. Original building, telescope still in use.


* NHR=National Historic Register

** NHL=National Historic Landmark


Authenticity and integrity 
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The Observatory building was expanded with two additions, the first in 1956 and a second larger addition in 1966. Although the original building has been enlarged, the original design, space and style are clearly evident and recognizable apart from the newer additions. Smaller auxiliary buildings and instrument piers in the south yard behind the Observatory have come and gone over the years.


Fig. 6. The Observatory from the south, taken in 2013. © Michael Svec


Documentation and archives 
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The Observatory’s instrument collection has been documented and is available online. The University of Illinois Archives also maintains several collections related to the Observatory including astronomers and alumni with associated with the Observatory.



Present use 
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The Observatory is currently used for office space and instruction. Instructional space incorporates the original 1896 building and the 1956 addition and is managed by the Astronomy Department and the College of Liberal Arts and Sciences. The 12-inch refractor and a classroom are used for undergraduate astronomy courses and monthly public open houses. During the spring 2014 semester, 2,400 undergraduate students used the Observatory and public open houses attracted another 500 visitors. Public open houses began in 1897. Fig. 7 shows the renovated telescope in 2014. Several university administrative offices occupy the 1966 addition.


Fig. 7. The renovated telescope, taken in 2014. © Michael Svec


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The University of Illinois employs a campus historic preservation officer and adopted a Campus Historic Preservation Plan in 1995. Plans for alterations and improvements to all campus academic facilities must be endorsed by the Office for Project Planning and Facility Management and approved by the Chancellor’s Capital Review Committee (CCRC). The Chancellor’s Design Advisory Committee (CDAC) must additionally review any proposed projects or major site improvements for historic buildings such as the Observatory.  The campus preservation officer serves on both the CCRC and CDAC.

The Observatory was listed on the US National Register of Historic Places on November 6, 1986 and designated a US National Historic Landmark on December 20, 1989. The Illinois Historic Preservation Agency (IHPA), the appointed affiliate for the US Department of the Interior, is responsible for protecting historic sites under the provisions of Section 106 of the National Historic Preservation Act and the Illinois State Agency Historic Resource Preservation Act. Any changes to the structure require review and approval by the IHPA. The university preservation officer and the CDAC consult with IHPA.


State of conservation 
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The Department of Astronomy and the University continue to maintain the facility so it can serve its original intention of teaching astronomy. The Friends of the Observatory works with the university to help ensure both preservation and conservation. The intent and desire is to keep the Observatory accessible and in-use for instruction.


Context and environment 
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The dominant characteristic of the campus is open and flat although the Observatory is built on a small knoll. Prior to 1896, the location was an experimental agricultural field. The adjacent Morrow Plots are a continuation of the agricultural field and are a dominant and protected feature of the campus. The Plots date to 1876 and provide an open space reflecting the early campus landscape. Along the perimeter of the property mature evergreen shrubs and trees provide a screen for ambient light. The space between sidewalks and the building are open grass areas consistent with the early campus landscape.

At the time of its construction the Observatory was the only academic university building on the south campus. Today the surrounding environment has changed and the Observatory sits near the very heart of campus. Its location on the southern boundary of the Main Quadrangle and near the main university library puts it near the center of campus activities.

Today the sidewalk and bicycle paths on the north and east sides of the Observatory are major pathways on campus with a high volume of pedestrian and bicycle traffic. The high volume of traffic around the Observatory increases accessibility for students and visibility but it also influences any alternation of the lighting or landscape favoring safety and security.


Archaeological / historical / heritage research 
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Most of the heritage research has focused on Joel Stebbins and his contributions to astronomical photometry. Stebbins himself spoke at Illinois during the 1957 American Astronomical Society meeting. The entire history of photometry was researched by Hearnshaw for his book The Measurement of Starlight: Two Centuries of Astronomical Photometry. Svec recounted Stebbins’ time at Illinois in an article in Sky and Telescope (1992) and another with Beaman in the Journal of the AAVSO (2012). The National Park Service documents the history in the applications for the National Register of Historic Places and the book Astronomy and Astrophysics. At present an alumni group, the Friends of the University of Illinois Observatory, is working to preserve the site and better document its collections and history.


Main threats or potential threats 
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The brick exterior suffers in some areas from efflorescence, mould growth and mortar deterioration due in large part to ineffective roof-water drainage. The floor joists on the first floor were modified in 1956 and now do not meet strength limits. The building additions have asbestos tiles. The utilities such as lighting, electrical, plumbing, heating, and air conditioning are obsolete and/or inadequate and have exceeded their service life.

Existing academic buildings occupy the northern and eastern site boundaries and the southern boundary is shared with the historic Morrow Plots. Underground Undergraduate Library and the South Quadrangle that the university is committed to maintaining as open space form the western boundary. The most recent campus Master Plan (2007) does not propose any new buildings adjoining the Observatory’s site.

Campus light pollution is a challenge. The university’s outdoor sports facilities are southwest of the Observatory flooding the sky with light during sporting events. The university does have a campus lighting committee that is primarily focused on a safe and secure campus. The 2013 Facilities Standards Overview does include the requirements for enhancing safety while minimizing glare and light pollution.


Management, interpretation and outreach 
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Management and maintenance of the building is the responsibility of the university in conjunction with the Astronomy Department and the College of Liberal Arts and Sciences. The scientific instruments are the responsibility of the Astronomy Department. Several thousand undergraduates use the Observatory each academic year as a requirement for the introductory astronomy classes. Advanced astronomy classes also use the telescope.

The University of Illinois Astronomical Society, a student organization that cooperates with the Astronomy Department, hosts public open houses once a month. In addition, Society members use the telescope when available. In 2011 a group of alumni created the Friends of the University of Illinois Observatory, which works with the Astronomy Department in supporting the preservation of the facility.



Bibliography (books and published articles) 
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Beaman, B., & Svec, M. (2012). Illinois – where astronomical photometry grew up. Journal of the American Association of Variable Star Observers, 40, 141–149. www.aavso.org/sites/default/files/jaavso/v40n1/141.pdf.

Hearnshaw, J.B. (1996). The Measurement of Starlight: Two Centuries of Astronomical Photometry. Cambridge University Press, Cambridge.

Myers, G.W. (1898). The Astronomical Observatory at the University of Illinois. Popular Astronomy, 6, 319–321. Online at SAO/NASA Astrophysics Data System (ADS).

Stebbins, J. (1957). Early photometry at Illinois. Publications of the Astronomical Society of the Pacific, 69 (411), 506–510. Online at SAO/NASA Astrophysics Data System (ADS).

Svec, M. T. (1992). The birth of electronic astronomy. Sky and Telescope (May 1992), 83, 496–499.

National Park Service (2001). University of Illinois Observatory, Astronomy and Astrophysics. National Parks Service Online Books. www.cr.nps.gov/history/online_books/butowsky5/astro4h.htm


Links to external sites 
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Friends of the University of Illinois Observatory

University of Illinois Observatory Collection


Links to external on-line pictures 
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University of Illinois Archives


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Thematic essay: Astronomy from the Renaissance to the mid-twentieth century

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