• Identification29/2
  • Title
    • Guide to the Dearborn Observatory Records
    • Dearborn Observatory, Records of the
  • LanguageEnglish
  • Date1863-1967
  • OriginationDearborn Observatory
  • Physical Description59.00
  • RepositoryNorthwestern University Archives Deering Library, Room 110 1970 Campus Dr. Evanston, IL, 60208-2300 URL: http://www.library.northwestern.edu/archives Email: archives@northwestern.edu Phone: 847-491-3354
  • AbstractRecords of Dearborn Observatory, built in 1865 by the Chicago Astronomical Society and the University of Chicago and in 1889 moved to Northwestern University's Evanston campus. Dearborn Observatory was a significant contributor in the area of double star research. The records consist almost entirely of observational data gathered by astronomers using Dearborn's 18½ inch refracting telescope or its meridian circle, calculations performed on the data, and the results of such investigations.

The Chicago Astronomical Society was founded in 1862 by a group of Chicago business and civic leaders who wanted to establish an observatory in Chicago. Aquaria, natural history museums, and observatories were considered educational and cultural concomitants of growing scientific inquiry and industrial technology, and their numbers grew substantially in the mid-nineteenth century.

By January 1863, sufficient funds had been raised through the sale of memberships in the Society to enable a committee to investigate various lens and purchase a suitable one. What was, at the time, the world's largest refracting lens became available as a result of the Civil War. Just prior to the War, Alvan Clark, America's foremost lensmaker, had ground an 18½ inch refractor for F.A.P. Barnard of the University of Mississippi. However, hostilities made delivery of the lens impossible, and the Chicago group was able to purchase it at a price of $11,187 including mounting.

The Society contracted with the original University of Chicago in July 1863 to house the observatory. Society member J. Young Scammon bore the cost of constructing the observatory tower and dome with the stipulation that it be named for his late wife, Mary Ann Haven Dearborn. W.W. Boyington designed both the tower and the dome. Construction began at 3400 S. Cottage Grove Avenue in the autumn of 1863 and the dome was completed in October, 1865. The lens arrived in Chicago on March 25, 1866, was mounted by Clark, and became operational on April 11, 1866. In addition to the equatorial, the Society was able to purchase a meridian circle with a $5000 donation from Walter S. Gurnee, Society member and former mayor of Chicago. Additional small instruments and books were purchased with donations from other Society members.

While the building was being completed, the Astronomical Society perfected its organization. The Society incorporated and elected its first officers during November and December 1865. At the same time a search was begun for a professional astronomer to direct the work of the observatory. On December 28, 1865, Truman H. Safford accepted an appointment as Director of the Observatory and professor of astronomy in the University of Chicago.

In addition to conducting celestial observations, the observatory initiated Chicago's first standard time service. The Chicago fire of October 8-9, 1871, brought research to a halt. The observatory was not damaged by the fire, but many of its most committed patrons, including J. Young Scammon who had been providing the director's salary, suffered severe financial losses as a result of the fire.

When it became clear that he would be receiving no salary for the foreseeable future, Safford requested and received a leave to join the U.S. Coast and Geodetic Survey. At the end of the leave, he accepted a position at Williams College instead of returning to Chicago. The Society's Executive Committee appointed Safford's assistant, Elias Colbert as Acting Director. Colbert was unable to engage in much research between 1872 and 1875, since he spent the majority of his time seeking funds to rehabilitate the observatory, the most pressing need being a replacement for the dome, which had proved highly unreliable. In 1875 Colbert reestablished the standard time service, and the $500 in revenue it generated comprised the bulk of his salary.

In 1876 Colbert announced his intention to resign as Acting Director. A talented amateur astronomer, S.W. Burnham, was appointed non-salaried Acting Director, but when it became clear later that year that Safford would not be returning, Colbert again assumed supervision of the Observatory. Colbert was successful in raising enough money to install a new dome and bring Alvan Clark to Chicago to recondition the lens.

In May 1879, Colbert retired and George Washington Hough was named Director. Hough launched an extensive program of observations, although he did not begin receiving a regular salary until 1881.

In June 1881, the virtually bankrupt University of Chicago's creditors moved to foreclose. There was concern that the Astronomical Society might lose title to the observatory's lens, meridian circle, other instruments, and library, but in 1886 the Cook County Circuit Court ruled that the scientific instruments and books could not be seized as payment for the university's debts. The observatory building, however, was ruled part of the university and liable to sale with other of the university's real estate holdings. In July 1887 the Society was informed that it had to vacate the building by October. Society board member and Northwestern University Trustee Oliver Horton proposed that the Observatory be moved to Northwestern's Evanston campus. An agreement between the Society and Northwestern was signed in August 1887, stipulating that Northwestern would construct a suitable building for the telescope and a house for the Director. The Director was to have the rank of professor in the university and his salary would be paid by the university. Northwestern would hold title to the building, while the Society would retain title to all the scientific instruments. The Astronomical Society would also retain its autonomy.

Hough supervised the removal of all instruments to temporary quarters in Evanston. University Trustee James B. Hobbs provided funds for a new building which was begun in June 1888 and dedicated June 1889. The total cost for a new building, designed by Cobb and Frost was $25,000. Hough recommenced observations with the 181/2 inch refractor in September 1889.

Hough continued as Director until his death on January 1, 1909. In September, Philip Fox was named Director. Fox instituted many improvements in the observatory equipment, most notably the replacement of mechanical recording devices with photographic techniques. Fox also built the first spectrograph for the 181/2 inch refractor. In 1910, the original mounting and telescope drive were replaced with a modern mounting and electric drive.

Prior to Fox's arrival the research carried out at Dearborn had been reported in scientific journals, including the Astronomical Journal and Popular Astronomy. Fox initiated the Annals of Dearborn Observatory in 1915 as a means of systematically reporting observations, editing the first two volumes of the Annals himself.

Fox resigned in 1929 to become the first Director of the Adler Planetarium. In April 1929 the Chicago Astronomical Society relinquished title to the telescope, meridian circle, and all scientific instruments to Northwestern, thus ending its sixty-six year association with the Dearborn Observatory. Fox was replaced by the assistant astronomer Oliver J. Lee, who served as Director from 1929 until 1947.

The most notable event that occurred during Lee's tenure was the relocation of the observatory building in 1939, necessitated by the construction of the Technological Institute. The twenty-five hundred ton building was jacked up, placed on rails, and pulled 664 feet south-southeast of its original site at the rate of twenty inches per minute. The observatory was out of service from June 18 to November 13, 1939. Aside from the need to recalculate the Observatory's precise longitude and latitude, the move had no adverse effects.

Lee retired in 1947 and was replaced by Kaj Strand. Strand served as Director for eleven years and maintained an active observational program. Upon Strand's resignation in 1958, the Directorship remained vacant for almost a year until J. Allen Hynek accepted the post. Hynek updated the observatory's facilities, pioneering the use of image-orthicon viewing systems, and the use of computers to analyze results. He also used the Dearborn facilities for several NASA projects. Under Hynek, the university opened an observatory in Organ Pass, New Mexico, and in 1967, the university dedicated the Lindheimer Astronomical Research Center. The new facility, with 40 inch and 16 inch reflecting telescopes and a wide range of computerized apparatus supplanted Dearborn as the university's primary astronomical facility. However, Dearborn's 181/2 inch refractor remained an active teaching instrument and provided free public viewings and tours. In 1975 Hynek retired and John Bahng became Director of Astrophysical Studies including responsibility for Dearborn.

From 1866 to 1967 the Dearborn telescope was used for a wide variety of observational projects. Under Safford and Colbert, the Observatory was used primarily in star cataloging projects. Dearborn contributed to the Astronomische Gesellschaft catalog until the Chicago fire limited all observations.

Perhaps Dearborn's most significant contribution was in the area of double star research. The existence of pairs of stars located close enough to each other that their gravities had an effect on each other's motion had been theorized by the middle of the nineteenth century, but prior to the grinding of the 181/2 inch refractor, no telescope had provided sufficient resolution to actually see a double star. During the testing of the newly ground lens in 1861, Alvan Clark made the first observation of the companion star of Sirius. After the lens was installed in Chicago, it was used by Burnham and extensively by Hough to study double stars. The first two volumes of the Annals of the Dearborn Observatory reported several hundred double stars discovered by Burnham, Hough, and Fox.

Hough carried on extensive observations of the planet Jupiter and was considered the foremost authority on the behavior of Jupiter's bands and spots. Fox carried out extensive research on stellar parallax, or the apparent displacement in direction of position of an object when observed from two points. Lee did considerable observation of Eros, an asteroid that periodically orbits closer to Earth than Mars does, and on huge, forming red stars.

Additional information on the Chicago Astronomical Society and its relationship to the Dearborn Observatory may be found in the holdings of the Chicago Historical Society. The Chicago Historical Society holds a manuscript history and minutes of the Society from 1862 - 1903, as well as the Society's Annual Reports, 1880 - 1887, and H.C. Rainey's two volume history of the Society.

  • Names
    • Chicago Astronomical Society
    • Dearborn Observatory
    • Burnham, S. W. (Sherburne Wesley), 1838-1921
    • Colbert, Elias, 1831-
    • Fox, Philip, 1878-1944
    • Hough, G. W. (George Washington), 1836-1909
    • Hynek, J. Allen (Joseph Allen), 1910-1986
    • Safford, Truman Henry, 1836-1901
  • Subject
    • Astronomical observatories--United States
    • Astronomy--Observations
    • Solar system--Databases
    • Stars--Observations

The Records of the Dearborn Observatory were transferred to the University Archives prior to June, 1974 as Accession #74-65.

Thomas J. Dorst, July, 1982

The records of the Dearborn Observatory fill fifty-four boxes and thirteen oversize folders. The records span the years 1863-1967, although the bulk dates from 1863-1941. The records consist almost entirely of observational data gathered by astronomers using Dearborn's 18½ inch refracting telescope or its meridian circle, calculations performed on the data, and the results of such investigations. Six folders of clippings, reports, and miscellaneous correspondence precede the observational records and two boxes of visitor's registers and material relating to the observatory's library follow the observational records.

The observational records created during the directorships of Truman Safford, Elias Colbert and George W. Hough were entered in notebooks, two hundred and five of which survive. Initially all observations were entered sequentially in notebooks. Separate records were kept for the equatorial (the 181/2 inch refractor) and the meridian circle. As various observational programs became more extensive, separate notebooks were created to record the results of the respective programs. The early notebooks are arranged as either equatorial or meridian circle observations and chronologically within oversize folders these categories, while later notebooks are grouped according to the subject of the observation.

The records include five and a half boxes, containing fifty-five volumes, of general observations made with the equatorial spanning the years 1863-1908 and the directorships of Safford, Colbert, and Hough. The majority of the observations were made by the three directors, although S.W. Burnham and several assistant astronomers contributed to the observations. The volumes include records of planetary studies, with observations of Jupiter, Uranus, and Neptune being the most numerous; stellar observations concerned primarily with fixing the exact locations and magnitudes of various stars; observations made to establish precise longitudes and latitudes; and observations of other celestial objects and events, such as asteroids, comets, and eclipses. In many cases the recorded data is not clearly identified, thus limiting its usefulness to all but experienced astronomers. For the most part, data recorded in the equatorial notebooks was not derived from systematic research projects and no narratives exist detailing the nature of the observations for the non-scientist.

Five boxes of meridian circle observations spanning the years 1868-1908 follow the general equatorial observations. The meridian circle was an instrument developed in the 18th and 19th centuries to establish the precise positions and proper motions of all bright stars. The planets, Moon, and Sun were then studied in relation to the meridian observations. The sixty volumes of meridian circle observations are arranged in categories according to the types of observations recorded as indicated in the titles of the volumes (Zero Stars, Great Catalogue, Working Lists, And general observations) and chronologically within each category.

Several worldwide cataloging projects were begun in the mid-nineteenth century. The Dearborn Observatory participated in a project directed by the Astronomische Gesellschaft in Berlin. Volumes of records document Dearborn's participation from 1868 until 1871 when the Chicago Fire curtailed research. Systematic meridian circle observations began again in 1879.

Notebooks detailing more specialized observations include seventeen volumes of occultation studies concerning the blocking of light from celestial bodies by other bodies, two boxes and one oversize folder of observations of Jupiter (see also the George Washington Hough Papers, Series 29/1), seven volumes concerning the Moon's parallax, and two volumes concerning a project to precisely measure the longitude, latitude and sizes of the Great Lakes. Following the volumes that record clearly identified specialized observations are three and one-half boxes of miscellaneous observations dating from 1863-1908. Some of the volumes have indications of their content, such as planets, zenith distance and Bradley stars. However, the majority oversize folders merely record observations and would require expertise in astronomy to be useful. The miscellaneous observations are arranged chronologically.

In addition to observational records from the period 1863-1908, the records include two boxes and three oversize folders of data pertaining to instruments used in the Observatory. The bulk of this data relates to Dearborn's standard time service, recorded in twenty-three volumes spanning the years 1869-1908. Also included are three oversize folders of meteorological data produced by Dearborn's printing barometer.

Following Hough's death, observational data gathered at Dearborn was no longer recorded in notebooks. With the directorship of Philip Fox, Dearborn's astronomical program was expanded, with the result that much of the actual observational work was done by graduate students. Fox instituted a regular reporting format that resulted in more clearly labeled records. Each sheet of observations records the observer's name, the date and the nature of the observation.

The records include one box of Fox's spectroheliograms that detail the sun's features by photographing it with monochromatic light. The bulk of the observational data from Fox's tenure concerns the stellar parallax measurement project.. Parallax refers to the apparent displacement in direction of an object when seen from two different, points not on a straight line with the object. The differing perspectives of a given star are created by observing it over a period of time as the earth moves in its orbit. Knowing the parallax for a star allows the astronomer to fix its position precisely by correcting for the parallax effect.

The records also include five boxes of parallax measurements taken between 1916 and 1929. Arrangement is chronological according to the date of the first observation made for a given star, even though in many instances a star was re-observed several times over as many as twelve years before a true value for its parallax could be calculated. The records indicate the identification of the star under observation by its name or its star catalog number, the name of the observer, the time and date of the observation, the observational data and the calculations resulting in an accurate parallax value.

In addition to the parallax measurements, there are one and one half boxes of reduction calculations which represent the determinations of the true positions of stars when corrected for parallax and proper motion error. (See also the Records of the Annals of the Dearborn Observatory, Series 29/3. Volume 3 of the Annals published Fox's parallax measurements and other volumes include further information on the stellar parallax project.)

During the directorship of Oliver Lee, several large projects were carried out. The records include one box of miscellaneous observations and five oversize folders of time clock records, 1933 to 1934. Also included are six boxes of records concerning Lee's observations of the asteroid Eros in 1930-1931. Eros' orbit brings it closer to the earth than any other large heavenly body besides the Moon. In 1931, Eros came within 13.8 million miles of the Earth, making it the subject of intense astronomical interest. The gravitational force of a large body passing so closely made it possible to more precisely measure the Mass of the Earth and the Moon, in addition to making close up general observations of the large asteroid itself. The records pertain to the measurements of the effects of the Earth on Eros and the changes caused in observed parallax. General observations of the character of Eros are also included.

The bulk of the observations during Lee's directorship document his Red Star Project from 1931-1941. Fourteen boxes detail Lee's study of huge-forming, red stars. The bulk of the data is arranged numerically according to folder numbers assigned by Lee, with the remainder arranged by photographic plate numbers or star name. The data pertains to the magnitude, or brightness of selected red stars and changes in their magnitude.

The only observational records from Hynek's directorship are two oversize folders of charts recording magnitudes of stars. The charts are not clearly labeled and require a sophisticated knowledge of astronomy to be useful. In addition, two oversize folders of miscellaneous observations and mechanical drawings of scientific instruments follow the main body of the records.