Schematic of Keplerian Refracting Telescope
All refracting telescopes use the same principles. The combination of an objective lens 1 and some type of eyepiece 2 is used to gather more light than the human eye is able to collect on its own, focus it 5, and present the viewer with a brighter, clearer, and magnified virtual image 6.
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"Schematic of Keplerian refracting telescope."
http://en.wikipedia.org/wiki/Refracting_telescope
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