12-inch equatorial refractor


12-inch equatorial refractor


Optical instrument
Measuring instrument


The telescope is a refractor with an objective of 12.4 inches clear aperture and of 15 ft. focal length. The objective is by J.A. Brashear of Allegheny, the curves used being those of Professor Charles Hasting. The objective is a doublet, or achromatic lens. Brashear used postage stamps to separate the two elements. The cell did have a small plate saying “J.A. Brashear, Allegheny Pa.” Brashear-Hasting objectives had the flint in front design. Flint is not typically the front lens because it was thought to be more susceptible to atmospheric attack and scratches. Hastings showed otherwise.

The telescope has a German equatorial mount on a rectangular cast-iron column of two-tons weight. The polar and declination axis are cylinders of steel three-inches in diameter. The tube consists of seven cylinders riveted together, six of 2.5 ft length and the seventh somewhat shorter. The sheets of steel composing the cylinders are 1/16 to 3/32 inches thick.

Two large graduated circles help with positioning the instrument. The right ascension wheel is 18.1 inches in diameter, graduated to 5 minutes. The declination wheel is 30 inches diameter graduated to single degrees for the same purpose in declination. The graduation marks of these coarse circles are streaks of white paint on a black back ground and are easily legible from the eye end of the tube in any position of the instrument. There exists a vernier scale for the right ascension but it is not longer operational. The vernier scale in declination is still operational and read from the eyepiece end of the telescope through 2 brass tubes. On the eyepiece of the declination reading telescope is marked "Gundlach Optical Rockchester NY."

The instrument is further provided with a driving clock. The original was replaced in the 1954 with a motor driving drive. Slow motion in both right ascension and declination was achieved by hand turned knobs at the eyepiece end of the telescope. Currently they are operated by electric motors. Right ascension and declination clamps are brought to the eyepiece. On the north side of the pier is a sidereal dial (clock work missing) and a wheel for coarse motion in right ascension.

The helioscope or finding telescope is 3.2 inches aperture and 4.5 ft. focal length, also by John A. Brashear. It has a brass tube and accepts 1 ¼ inch eyepieces.

The telescope came with a filar micrometer (see below), 6 negative eyepieces, 1 zenith prism, 1 helioscope (finder) and the plate camera (see below). Added 8 weights and bracket in fall 1911, also worked on the worm. According to Warner & Swasey, it was designated M-42, two other telescopes of this type were sold to Dudley Observatory in New York and American University in Beirut, Syria. The Dudley Observatory telescope is currently in storage.

The telescope was assembled in November 1896. In a March 6, 1897 letter to President Draper, director G.W. Myers noted “The equatorial room, not having been finished on the interior, the unpainted interior surface of the wooden dome is continually exposed to the moisture of the air, which causes the dome to become deformed so seriously during damp weather as to make it well nigh impossible to mange it for several days thereafter. The open condition of the room also contributes seriously to the difficulty. Under present conditions, the $5000 equatorial must necessarily injure rapidly from exposure. Half a dozen times since the instrument was mounted last Nov. a sheet of ice chrystals [sic] has formed over the lens from the excessive moisture of the room, so thick as to render observations temporarily impossible. This condition of things must injure the lens in time if not obviated.” Money was appropriated to paint and caulk the room.

“When the writer (Joel Stebbins) took charge of this Observatory in 1903, he found that the 12-inch objective had not given satisfaction for some years. The out of focus image were elliptical, and with good seeing the definition was rather poor. However, the lens was far from useless, and it seemed best to go ahead with the program of double stars, most of which were easy objects for an instrument of this size. During the summer of 1905, the writer was to be absent from the Observatory, and the lens was shipped to Allegheny at the request of Mr. Brashear, who naturally became interested when he learned that an objective of his manufacture was not giving satisfaction. He found that the metal ring which holds the lenses in the cell had been pressed down on one side, and allowed to remain, causing a permanent bending, principally of the flint lens. Although he was in no way responsible for this occurrence, Mr. Brashear kindly refigured both lenses without cost to the Observatory, and the objective was returned in October 1905. The defects were corrected, and now we have a first class objective.”

The telescope was restored in 1953 by J.W. Fecker Inc. for $15,000. The telescope was disassembled about April 10, 1953 and sent to Pittsburgh. It was returned later that summer using a better quality crane than the one used to remove the telescope. At that time, the gravity driven drive, the manual slow motion controls, the right ascension vernier scales, and the right ascension friction wheels were removed and the telescope was updated with electric motors. The dome motor was also replaced. In the late 1980s, members of the astronomy club cleaned the recent paint off the telescopes’ brass tail piece and improved the telescopes’ electronics.

The telescope was restored for a second time during the summer of 2013 by Ray Museum Studios of Swarthmore, Pa.


Warner & Swasey Company, Cleveland, Ohio and
John Brashear, Allegheny, Pennsylvania.


Stebbins, J. Photometric Observations of Double Stars. The University Studies. Vol. 2, no. 5. July 1907. University of Illinois Press.

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


Astronomy Department, University of Illinois, Urbana, Illinois




Michael Svec


copyrighted by Michael Svec






physical object


University of Illinois Observatory collection A101, A105


University of Illinois Observatory, Urbana, Illinois





Warner & Swasey Company, Cleveland, Ohio and John Brashear, Allegheny, Pennsylvania., “12-inch equatorial refractor,” University of Illinois Observatory Collection, accessed May 10, 2021, https://uiobservatory.omeka.net/items/show/1.