Reflecting Telescope

A reflecting telescope forms an image using a single curved mirror, or a combination of curved mirrors, to reflect light. Isaac Newton invented it in the seventeenth century as an alternative to the refracting telescope, which at the time suffered from severe chromatic aberration. Reflecting designs introduce their own kinds of optical aberration, but they allow for much larger objective diameters, which is why almost all major research telescopes in astronomy today are reflectors. Many variant designs exist, some adding extra optical elements to improve image quality or to place the image somewhere mechanically convenient, and because they rely on mirrors the design is sometimes called a catoptric telescope.