30-inch mirror
Astronomy
Optical instrument
Telescope
Wood, metal, glass
Frustrated by the selenium cell photometer's lack of sensivity, Joel Stebbins purchased a large 30-inch reflector in 1912. The original telescope was purchased from C.W. Draper, $1500, #573, July 26 1912. It has previously been owned by Elmer Gates who used the telescope as a burning glass. According to Robert Baker: “The original telescope was made by the Brashear Company after the specifications of an individual whose plan was apparently not astronomical. According to one account he purposed using it as a burning glass for manufacturing diamonds. Another story is that he expected to observe the flight of souls. However this may be, the instrument was finally on the market at a very small price and my predecessor, Professor Joel Stebbins, recommended its purchase by the University. The telescope was quite unusual as its original purpose appears to have been. The 30-inch mirror had a focal length of only 20 inches and such necessarily imperfect definition that it was not the easiest matter to distinguish between a star and the moon.” A 1914 article in the Urbana Daily Courier states that the original mirror was by Brashear and was used in Washington DC as a huge burning glass, used to melt platinum.
Once in place, Stebbins and his assistant Elmer Dershem used the 30-inch telescope as a test bed for the selenium photometer as late as 1919. The photoelectric cell photometer being used in the main Observatory was proving to be very sensitive so the work on the selenium cell was eventually ended by the time Stebbins left Illinois in 1922.
Since the original Brashear mirror had proven unsatisfactory, a new mirror was ordered around 1925. The new primary mirror was 29 ½ inches in diameter, 4-inches thick with a 4-inch hole in the center. The missing secondary mirror was 7-inches in diameter. Both were made of borosilicate crown glass figured by John E. Mellish, an amateur telescope maker turned profession located outside of Wilmette Illinois around 1925. As an amateur he discovered six comets and is credited with being the first to see craters on Mars. The new focal length of the primary was 75-inches and the focal ratio of the Cassegrain system was 12.
The original mount from 1915 was an equatorial with a fork mounting. It was later adapted to the new 30-inch telescope in 1925 and to the Ross camera in 1939. The wooden dome was constructed in 1915 with a double slit.
With the new optics and longer focal length, the telescope mount needed to be modified. Six brass rods supported the secondary mirror in its new position. Focus was achieved by racking the secondary along the optic axis of the primary. Slow motion controls and clamps were added as were long counter-balance weight rods. The clock drive was also modified to handle the extra load. The 30-inch observatory's new site was on the south side of Florida Avenue, just east of Wright Street, about a quarter mile south of the Observatory. The site had darker skies courtesy of a cemetery to the north and crop fields to the south. The telescope was operational by December 1927. In 1938 Baker replaced the 30-inch mirror with a 4-inch Ross Fecker camera.
Currently on the Mellish 30-inch mirror remains. The mirror has lost the silver coating and has a 7-inch crack but test have shown it still retains it’s figure.
John Mellish
Baker, Robert H. "The 30-inch Reflecting Telescope and Photoelectric Photometer of the University of Illinois." Popular Astronomy. 122:86-91.
"University buys big telescope" (August 5 1914) Urbana Daily Courier, page 3.
Astronomy Department, University of Illinois, Urbana, Illinois
1927
Michael Svec
Copyright MIchael Svec
image/jpg
English
physical object
University of Illinois Observatory, Urbana, Illinois
Lantern slide 'U of I 30 inch reflector'
Astronomy
Photography
Optical instrument
Telescope
Lantern slide of the 30-inch reflecting telescope purchased in 1914. The mirror had a focal length of 20-inches and was made by John Brashear. The mount might also be by Brashear. This lantern slide is part of the Observatory's collection and is marked "O 60."
According to a 1914 article in the Urbana Daily Courier, the telescope "has been in use in Washington D.C. for some time but is now in the Metal Shop awaiting the completion of the new observatory where it will be installed. The telescope has been used for condensing the rays of the sun onto a mirror. The instrument has been used to melt platinum which requires about 1775 degrees Centigrade. The mirror was a diameter of thirty inches. The focus is very short so that there is a maximum of light-gathering properties making it a huge burning glass. It has been set up at the Metal Shops and carefully tested. It was constructed by the John Brashear Company of Pittsburgh." The goal for this new telescope was to have it equipped with a photoelectric photometer.
Photographic department, University of Illinois
Baker, Robert H. "The 30-inch Reflecting Telescope and Photoelectric Photometer of the University of Illinois." Popular Astronomy. 122:86-91.
"University buys big telescope" (August 5, 1914) Urbana Daily Courier, page 3.
Astronomy Department, University of Illinois, Urbana, Illinois
circa 1914
still image
English
University of Illinois Observatory, Urbana, Illinois
6-inch f/16 equatorial refractor by Jeslerski
Astronomy
Optical instrument
Telescope
Metal, brass, glass, wood
Donated by Mrs. Ruth Scott of Chrisman Illinois in 1971. Equipped with solar filter, diagonal, slow motion, 60 mm guide telescope, 25 and 50 mm finders, equatorial mount on heavy movable wooden tripod. Valued at $1,500 in 1971. Very little is known about Jeslerski (1888-1944) and few telescopes by him are documented. He was an ethnic German who immigrated from Poland to Chicago. He did advertise in Popular Astronomy in the 1930s. Matches a set of 4 eyepieces, right angle prism and Hershel wedge marked with the letters “TEJ.”
Theodore E. Jeslerski, Chicago, Illinois
Astronomy Department, University of Illinois, Urbana, Illinois
circa 1935
Michael Svec
Copyright Michael Svec
image/jpg
English
physical object
University of Illinois Observatory Collection A219
University of Illinois Observatory, Urbana, Illinois
12-inch equatorial refractor
Astronomy
Optical instrument
Telescope
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
1896
Michael Svec
copyrighted by Michael Svec
image/jpg
English
physical object
University of Illinois Observatory collection A101, A105
University of Illinois Observatory, Urbana, Illinois