12th physics. NCERT notes

Reflecting type Telescope (Cassegrian telescope)

In such telescope, one objective lens is replaced by a concave parabolic mirror of large aperture, which is free from chromatic and spherical aberrations.

In normal adjustment, magnifying power

Advantages of Reflecting type telescope

  1. There is no chromatic aberration as the objective is a mirror.
  2. Spherical aberration is reduced using mirror objective in the form of a parabolic.
  3. The image is brighter compared to that in a refracting type telescope.
  4. Mirror requires grinding and polishing of only one side.
  5. High resolution is achieved by using a mirror of large aperture.
  6. A mirror weights much less than a lens of equivalent optical quality. Therefore, mechanical support of mirror is much less of a problem compared to the support required for the lens. Further mirror can be supported


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