3-inch combined transit and zenith telescope


3-inch combined transit and zenith telescope


Optical instrument
Measuring instrument


Metal, glass

The principle transit circle was a 3-inch Combined Transit and Zenith telescope designed by Warner & Swasey especially for Illinois. The objective, by John Brashear, was held in place by a special cell that compensated for the different temperature conductivities of the brass and glass so that temperature had no effect on the location or separation of the lenses. Designated as model M-505, the transit includes a handing level, micrometer with a reticle contained a series of 5-3-5-3-5 parallel lines etched onto glass, and a built in reversing mechanism. This transit was located in the east-central transit room allowing direct access to the clock room through a small window. A basin of mercury (mercury now removed) in the base of the transit was used for vertical collimation and nadir observations. Marked with a Warner & Swasey plaque and a smaller J.W. Fecker plate added after the April-June 1953 restoration.

The transit circle was capable of determining both right ascension and declination. Installed February 20th 1897 and dismounted in 1974 because of the condition of the roof and shutter. The instrument cost $1200, and was the first of five 3" combined transit and zenith telescopes. Additional M-505 were built for Park College (1897), Warner & Swasey Observatory at Case Western Reserve University (1898), Lafayette College in Easton PA (1906) and the Elgin Watch Company in Illinois (1909). The Park College telescope was stolen in the late 1980s and the observatory no longer exists. The Traill Observatory at Lafayette College was torn down in 1929 and Warner & Swasey Observatory in Cleveland is abandoned. The transit was featured in Warner and Swasey’s 1900 portfolio “A Few Astronomical Instruments.”

Myers’ description of the instrument: "The combined transit and zenith telescope has a Brashear objective of three inches diameter and a focal length of 37 inches. It has two graduated circles, one of 12.5 inches diameter, graduated to half degrees and read by verniers to minutes, and the other of 12 inches diameter, graduated to 10 minutes and read by verniers to 10 seconds. Delicate striding and zenith telescope levels, together with a micrometer that may be used either in right ascension or declination render the instrument capable of yielding very excellent data whether used as a transit instrument or as a zenith telescope.

“The larger part of the weight of the horizontal axis, which by reason of its system of circles, levels, etc., is subject to considerable flexure, is borne by a pair of friction rollers, held by springs against cylindrical bearings at either end and about 2 ½-inches within the pivots. Only enough weight is allowed to come upon the pivots to make them rest firmly in the wyes.

“By suitable combination consisting of a level, a graduated circle and a reversing apparatus the west pivot may be brought into the east wye and the instrument reset upon the same star with extreme quickness and perfect safety. In addition to the above mentioned facilities, the instrument is supplied with a mercurial horizon, a complete set of eye pieces, including a collimating and a zenith eye piece. All in all, this instrument leaves little to be desired in either point of convenience or of completeness."

One of Warner & Swasey’s most important achievements was the construction of a Dividing Engine in 1880 for automatically graduating circles of 40-inch or less in diameter. The greatest errors made by this machine were less than one second or arc. This instrument was used to make the vernier scales for all of their telescopes and transit telescopes including both the Illinois transit and equatorial. Warner & Swasey built a 6-inch transit circle for the U.S. Naval Observatory in 1898 and remained a premier astrometry instrument for almost a century.

C.M. Huffer remembered using the transit in the course Practical Astronomy about 1916 for the determination of time and position. Astronomy club president F. Samuel Bauer remembers that in 1962 "Equinoxes were a special time for students, in that they were celebrated by timing them. Using the transit instrument, an ad hoc group would fire up the shortwave radio in the timing room and get the ink flowing on the chronograph, with the WWV signal providing timing blips. Other members would use the transit telescope to time the passage of a chosen star to determine the exact time of the equinox sending 'wire crosses' to the chronograph pen by telegraph key."


Warner & Swasey Company


Warner & Swasey. (1900). A few astronomical instruments. From the works of Warner & Swasey, Cleveland, Ohio. Warner & Swasey: Cleveland.

Myers, G.W. (1898) The Astronomical Observatory. Technograph. 11: 105-111.


Astronomy Department, University of Illinois, Urbana, Illinois




Michael Svec


Copyright Michael Svec






physical object


University of Illinois Observatory Collection, A110
University ID 016647


University of Illinois Observatory, Urbana, Illinois




Warner & Swasey Company, “3-inch combined transit and zenith telescope,” University of Illinois Observatory Collection, accessed July 15, 2024, https://uiobservatory.omeka.net/items/show/3.