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What Do the Different Lenses of a Telescope Do?

People have dreamed about the stars, created myths and legends about them and used them to predict the future. Scientists have sought ways to peer into the universe to understand its structure and movement, to predict meteor showers and to anticipate the arrivals of comets and asteroids. The different lenses of telescopes make it possible for people to bring the universe down to earth.

How Telescopes Work
- View a nebula through a telescope.
  
  Telescopes gather light from distant stars, planets, nebulas or other objects in space and focus the images for viewing or recording. Telescopes use arrangements of lenses and mirrors inside of cylindrical tubes to view objects at various distances from earth. Larger lenses and mirrors are capable of collecting light from more distant objects in space.
Objective Lenses of a Refracting Telescope
- The objective lenses collect light from distant objects.
  
  A refracting telescope has a set of two or more lenses in the end closest to the sky. These lenses work together as a unit called the "objective," which collects the light from distant objects and organizes the light rays into a detailed image.
Eyepiece Lenses of a Refracting Telescope
- A girl focuses the image in the eyepiece.
  
  The lenses in the eye piece control the magnification of the image. The eyepiece also allows the person viewing the image to adjust the focus and accommodate for near-sightedness or far-sightedness. The human eye contains the final lens that processes the image from a telescope. The lens of the eye sends the image to the brain.
Role of Lenses in Reflecting Telescopes
- A reflecting telescope uses mirrors instead of lenses for the objective.
  
  Reflecting telescopes use curved mirrors instead of lenses to bring light into the telescope and focus the image. A reflecting telescope may use a series of mirrors to focus the light into an image. In a reflecting telescope, the lenses in the eyepiece work the same way as in a refracting telescope to magnify and sharpen the image.

Astronomy