Refracting Telescope

A refracting telescope is a type of optical telescope that uses a lens as its objective to form an image. The design was originally used in spyglasses and astronomical telescopes and is also used today for long focus camera lenses. Large refracting telescopes were very popular in the second half of the nineteenth century, but for most research purposes the design has since been superseded by the reflecting telescope, which allows larger apertures. A refractor's magnification is calculated by dividing the focal length of its objective lens by that of its eyepiece.