It is an optical instrument that allows you to view distant objects with much more precision than with the naked eye to capture electromagnetic radiation such as light. This is an important tool in astronomy and each development or refinement of this instrument has allowed great advances in the understanding of the universe. In 1609 Galileo Galilei designed and built the first recorded astronomical telescope. Thanks to him, great astronomical discoveries were made.

This was previously known as “spy lens”, the name “telescope” was proposed at a dinner held in Rome in honor of Galileo on April 14, 1611 by the Greek mathematician Giovanni Demisiani, in which the members of the meeting could observe the moons of Jupiter through the telescope, this device being brought by the famous astronomer.

The most important parameter of a telescope is its objective lens. The telescope is generally between 76 and 150 mm in diameter that allows observing some planetary details and many deep sky objects such as galaxies, clusters and nebulae. Telescopes measuring over 200mm in diameter allow you to clearly see important planetary details, fine lunar marks, and a large number of nebulae, clusters, and bright galaxies.

There are several types of telescopes:

  • Refractors: which are those who use lenses.
  • The reflectors: are those that have a sunken and curved mirror in place of an objective lens.
  • Catadioptric: they also have a mirror with a curved and sunken shape and a correction lens that also supports a second mirror.

It was Isaac Newton in 1688 who invented the reflecting telescope and thus constituted an important advance in the telescope by easily correcting the main characteristic chromatic aberration of the reflecting telescope.

To characterize the telescope and use it, a series of parameters and accessories are used:

  • Objective diameter: diameter of the primary mirror or lens of the telescope.
  • Barlow lens: lens that generally doubles or triples the ocular magnification when observing the stars.
  • Filter: it is a small accessory that generally dulls the image of the star, depending on its size and color, which can improve observation.
  • Focal ratio: it is the quotient between the focal length and the diameter.
  • Eyepiece: it is placed on the telescope lens and allows to magnify the image of objects.
  • Limiting magnitude: it is the maximum magnitude that can be observed by the telescope.
  • Increased: it is the number of times that it doubles in size.
  • Tripoid: Set of three legs that provide support and balance to the telescope.

  • Eyepiece holder: hole where the eyepiece is placed.
  • Focal length: is the focal length of the telescope.