The telescope

It is an optical instrument employed to observe very large objects that are found very distant as for example stars, comets, planets, between others. The first person that discovered this instrument by chance was the eyewear manufacturer Hans Lipeershey a certain day when was supporting in each one of his hands a lens and upon watching through could observe to great distance the rooster of the very nearby cathedral to him, then he mounted the lenses in a pipe in order to preserve the relative distances of the lenses. In this way he invented one of the optical instruments of more help for the humanity and for the scientific field to discover the fabulous mysteries of the Universe.

The news of this discovery traveled all over the countries, then Galileo Galilei also decided to manufacture one own to which called the telescope, focusing to the sky he could observe the four satellites of Jupiter, the craters of the moon, the Venus phases, the solar stains and multitudes of little brillant stars that they can not be seen simply by the human eye.

All those observations accomplished by Galileo were accomplished with a small microscope with a length not to exceed to 1 meter. But as the stellar observation is indifferent, concerning the position of the image that were obtained, Galileo used the telescope with two convergent lenses that gave an inverted and virtual image.

In order to have a greater quantity of information little by little the telescopes were being made larger and of greater diameter what was implying every time of greater diameter and with of the lenses. In the year of 1656 Christian Huygens built a telescope of approximately 7 meters of long and he could observe the rings of Saturn, but every time the persons that were manufacturing telescopes were trying to building them largest found with a technical problem, that the lens between larger was, the image of the observed object were become blurry and was showing a chromatic band to its around.

Credits: Villegas

With the studies accomplished by Isaac Newton above all what is referring to lenses with the zeal of solving this problems, found the reason of that defect, in the fact of the difference in the deviation that were presenting the different colors, since each one of these is characterized by having its own wavelength.

In 1633 the Scottish mathematician Jaime Gregory designed a reflection telescope and five years after be designed this instrument Newton built with success the first telescope of that type. Of that form he replaced the lens of object by a concave mirror, that's how it suppressed the inherent chromatic aberration to the images formed in the lenses.

Credits: Villegas

The figure that is illustrated below explains how is obtained the image in a refractor telescope employed for the astronomic observation. The used lenses are biconvex in the objective as well as in the visual and the image that is obtained is virtual and inverted.

The object A is found at great distance from the telescope. The image that is obtained from this object is real, smaller and inverted and it'is formed between the area of the visual lens and the lens; it serves at the same time as object for the visual that produces from this image A'1 other image A'2, straight and virtual.