CHAPTER 1Astronomical Telescopes
What is a telescope? It is an instrument that forms an image of a distant object, and it is thanks to a marvelous property of light rays -- that they can be bent or "refracted" by a piece of glass, or reflected by a shiny surface -- that telescopes are possible. With mirrors, or glass lenses, we can manipulate light rays in any way we wish, casting images of remote objects onto the eye's highly sensitive screen, the retina.
Countless nerve endings then transmit the color and intensity responses from different parts of this image to the brain, which in turn decodes the information and...