Refractor and Reflector

Refractor and Reflector

. The Sun can be observed with both refractors and reflectors. The earliest telescopes were refractors (left). The curved surfaces of the lens bend the incoming parallel solar light rays and bring them to a focus at the center of the focal plane, where an image of the Sun is created. The reflecting telescope (right) uses a large, parabolic primary mirror to collect and focus light. The prime focus can be used for direct images by removing anything that intervenes in the light path. Large equipment, such as a spectrograph, requires a more mechanically stable platform, so the Cassegrain focus is often used. For massive equipment, the light might be further reflected to the Coudé focus.

Copyright 2010, Professor Kenneth R. Lang, Tufts University