Moon Hits Your Eye
Through Largest Refractor Telescope
Published in Chicago Daily Herald
By Maryan Pelland
Yerkes Observatory in Williams Bay, WI., a pleasant 45-minute ride from Chicago, is a good place to let the stars get in your eyes. The observatory is operated by the University of Chicago and houses the largest refractor telescope in existence on this planet.
A refractor telescope, according to Yerkes public relations specialist Richard Dreiser, is one that uses two lenses, one at the eyepiece and one at the front end of the telescope. These lenses are very expensive to make, extremely heavy and hard to align, but they gather enough light to allow scientists to study hundreds of billions of nebulae, stars and space objects invisible to the human eye.
Dreiser said, "The Yerkes telescope, built over five years between 1892 and 1897, is the 40th largest of all telescopes. It is the last and largest of a long line of giant lens-types built in the 19th century, and is still completely functional today."
Reflector telescopes, more commonly built and used today, are less expensive. A much smaller reflector type scope, which uses a mirror to do the light gathering, makes seeing space less costly and far easier. Though it is possible to buy small refractor scopes, Dreiser says those are not used in observatories, they are more for hobby use.
He pointed out that the century old telescope at Yerkes has the largest light gathering capability of any lens-type scope in the world. Scientists can use photographic plates attached to its lens to create a photographic negative of the moon that is 7.5 inches across (a 35 mm negative is less than 2 inches across). This large of an image allows a clear and highly detailed view of craters, mountains and other geographic figures that are as small as one half mile across.
The telescope, which is shown to the public on Saturdays year round, weighs in at a whopping six tons. It is 52 inches in diameter (the lenses are 40 inches), the tube-housing is 64 feet long. This massive antique rests on a cast-iron base that weighs 50 tons. The telescope and base are mounted through a whole in a round wood platform floor, 70 feet wide. The hardwood floor is suspended from four sets of cables and pulleys allowing the floor to be raised or lowered to bring astronomers and their instruments up to the telescope as needed.
Tucked away in the basement of this architectural gem are labs, offices, workrooms and an $800,000,000 piece of equipment that works on adaptive optic projects to enable scientists to see stars far more clearly. "I love knowing I can go down there and handle an $800,000,000 gadget," quipped Dreiser.
The building itself was built in the shape of a Roman cross. It has three observation domes and several smaller telescopes. All of the engineers from the University are based there. From the beginning, some very serious work has been accomplished by Yerkes Observatory scientists, including the development of the theory that our galaxy, the Milky Way, is spiral in nature. The definitive journal for astronomy, the Astro-Physical Journal, used by scientist all over the world, was born at Yerkes in 1901. The first edition was a single 680-page volume covering all the advances made in astronomy during that year. Now, each edition is composed of about 1000 pages and covers a single month.
Currently, Yerkes scientists and engineers are developing tools and instrumentation for space exploration in programs like the Sojourner mission to Mars and the Sofia next-generation airborne observatory. University students use the Yerkes telescope for astronomy during the academic year, while junior high and high school students are invited to astronomy camps at the observatory during the summer. Some of the work done there requires the use of telescopes, but these days, much of it does not.
Oddly, says Dreiser, "The man who was responsible for the development of the Yerkes telescope, George Ellery Hale, was also responsible for the demise of its type - he developed the mirror type telescope that is more common now. The observatory was named for Chicago streetcar magnate Charles T. Yerkes, who helped fund the project."
Hale had a life-long ambition to study the sun. When the University of Southern California abandoned a plan for a giant telescope, he encouraged the University of Chicago to buy the huge glass disks that had been imported from France. A 53-acre tract of land was donated for the project and a beautiful ornately detailed observatory was designed by Henry Ives Cobb, architect of the University of Chicago. The pastorally handsome site is on the northwest end of Lake Geneva.
Dreiser conducts tours for the public on Saturdays at 10 am, 11 am, and noon. They take about one hour and include a question and answer session. Private tours and astronomy programs can be arranged for large groups - but some fees apply. The observatory houses a small museum and a large collection of photographs, charts and astronomical information. Call 608-257-4640 or visit http://astro.uchicago.edu for directions.