Telescope: Refracting

Large refracting telescope with 18 1/2 inch objective lens (lenses now removed). "ALVAN CLARK & SONS,/CAMBRIDGE, MASS./1864". This large refracting telescope, known as the Dearborn Refractor, testifies to the nineteenth-century race for ever bigger and more powerful instruments. With a 18.6-inch aperture, it was the largest telescope in the world from 1862 to 1868.