Compendium of Practical Astronomy

pp 59-136

Optical Telescopes and Instrumentation

  • H. Nicklas

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Most instruments employed for astronomical observations are designed primarily to increase the intensity of illumination on the surface of an image-recording device, be it a conventional photographic plate, a sophisticated electronic detector, or merely the human eye. This may be achieved by enhancing the light-collecting area or by sharper imaging, with the aims of improved angular resolution in order to separate closely adjacent objects and high light-gathering power in order to clearly pick out faint objects. There is no all-round, “universal” instrument available that satisfies all of these requirements simultaneously. Rather, an observing instrument is optimized for a specific purpose and is often named after a particular type of construction or observational mode (e.g., zenith telescope, transit circle, binoculars, rich-field telescope, coronograph, astrograph, or Schmidt camera).