The 40-inch refracting telescope at Yerkes Observatory in Williams Bay, Wisconsin, contains the world’s largest refracting lenses. Built in 1895, the telescope and observatory are owned by the University of Chicago. Making several important astronomical discoveries in the 20th century, the Yerkes Observatory has come to be known as one of the birthplaces of modern astrophysics, attracting many famous astronomers to Williams Bay.
Refracting telescopes consist of two convex lenses.The telescope at Yerkes Observatory was significant because it surpassed the 36-inch refracting telescope at the Lick Observatory in California, making the Yerkes telescope the largest refracting telescope in the world.
Photography began playing an important role in advancing research in the early 20th century. The 40-inch refracting telescope at Yerkes Observatory was one of the first telescopes optically designed for photography over human vision to create higher quality pictures.
Among the prominent scientists to study at Yerkes was Edwin Hubble, who did his graduate work at Yerkes. The Yerkes telescope also discovered the atomic explosion of the star named T-Corona Borealis and took pictures of globular star clusters, which helped with the study of star motion.
But almost as soon as the telescope at Yerkes was completed, astronomers switched from refracting to reflecting telescopes. Refracting telescopes produced images that are blurred because different light wavelengths refract at different degrees. The manufacture of refracting lenses was also complex and expensive so it made more economical sense to build cheaper, reflecting lens telescopes. Yerkes was the last and biggest refractor ever made.