Galileo's Telescope

by Peter Tyson

Sir Isaac Newton once wrote, in what must be one of the most oft-quoted lines in the history of science, "If I have seen further it is by standing upon the shoulders of giants." Well, any of us who has ever looked through a telescope could say the same, for the two principal types in use today were developed by giants: the refractor by Galileo and the reflector by Newton. Those two scientific geniuses, as Sir Isaac himself acknowledged, built upon the work of others, and how they came to design their inventions offers a compelling glance at the workings both of the telescope and of the scientific process itself.

In Galileo's version, light entering the far end (1) passed through a convex lens (2), which bent the light rays until they came into focus at the focal point (f). The eyepiece (3) then spread out (magnified) the light so that it covered a large portion the viewer's retina and thus made the image appear larger.

Source: http://www.pbs.org/wgbh/nova/galileo/telescope.html