Translations of Encyclopedia about Physics

Telescope

Telescopes or binoculars enable us to observe objects located at a very far distance. From the point of view of optics, microscopes also belong to the family of telescopes. With microscopes, we are able to view very small objects, often not visible to the human eye.

There are many types of telescopes. The Dutch or Galileo’s telescope uses a converging lens with a large focal point distance for the objective (the lens closest to the observed object) and a diverging lens for the ocular lens (the lens located closest to our eye) which, together, offer the observer a direct (unreversed) image of the object. Telescopes of this type are often constructed in duplicate and in which the flow of light rays are divided prior to their entry into the ocular but diverted to two separate oculars, a design used for opera viewers or binoculars (lesser magnification).

With Kepler or star gazing telescopes, used above all in astronomy, the ocular and the lens are made up of one or more converging lenses. Such devices magnify the object being viewed but reverse it by 180°, which can then be corrected back to normal using another set of lenses. However, this complex system of lenses results in a major loss of light, which is why star gazing telescopes no longer use this technology.

Terrain or ground telescopes, which serve to observe objects located on the ground, have a third converging lens located between the objective and the ocular lenses. This third lens reverses the image so that the final image visible to the human eye is right side up.

Prismatic telescopes are those which use two prisms, located between the objective and ocular lenses, instead of a converging lens to reverse the image back to normal. Here, one prism reverses the upper and lower ends of a flow of light beams, where the other prism reverses the left and right ends, to generate a final image which appears right side up when viewed through the ocular.

Distance is measured using infrared rays. This type of measuring is accomplished by using an emitter of infrared rays and a receiver located at a certain point. The measured distance is then calculated by comparing the phases of the reflected and directly received (reference) rays.

The principle of the telescope is a fine example of the many uses one can find for optical lenses and shows us that, with the help of various types of lenses and their organisation, we can view objects and phenomena not visible to the human eye.

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