How do Astronomical Telescopes Work?
Astronomical telescopes all work on the same principle: a main optical device is producing at a distance a magnified image of the object observed. An eyepiece there -an eyepiece is a secondary optical device- is further magnifying the image. The final power, or magnification, is a ratio of the focal length of both the primary and the eyepiece optics. The focal length of an optical device is the point where the image of the object observed is formed and in focus. A given telescope yields various magnification values depending on what eyepiece is used. A telescope with a focal length of 700 mm used with a 20 mm eyepiece yields a power of 35 x as the same telescope used with a 10 mm eyepiece yields a power of 70 x. Manufacturers generally offer an eyepieces’ range sufficient to give each telescope about 6 or 7 magnification values. The same is true of the telescopes and the eyepieces ranges purchased independently as independent manufacturers are working on such basis too. The important i
