Today, people perceive telescopes as routine commodities which have existed for decades and centuries. Now, it is impossible to surprise modern people by a telescope with the help of which they can have a look beyond the Solar system, while just a few centuries ago, such a possibility would be perceived as heresy since it was absolutely unbelievable. Nevertheless, it did not prevent scientists working at the epoch from developing their researches in the field of optics, which has not been shaped as a science yet and by the early 17th century first telescope were created in Europe. In this respect, it is important to lay emphasis on the fact that the creation of a working telescope was rather a product of several scientists working on the creation of the prototype of the modern telescope and their findings were used by Galileo who created a telescope with a consistently improved design and which was the main prototype of later telescopes.
In actuality, it should be said that the development of optics, including ideas and attempts to create device tools, which could be used as modern telescopes, date back to the middle ages and antiquity. At this point, it is important to lay emphasis on the fact that the creation of telescopes is inseparable from the development of optics. The origin of optics dates back to the epoch of antiquity, when Ptolemy, in his work “Optics”ť described properties of light, which were crucial for the invention of telescope, including such properties as reflection, retraction and color. His ideas were later developed by Roman scientists. But the development of optics as a fundamental science, without which the invention of telescope would be impossible, continued.
However, after the downfall of the Roman Empire, the center of optics moved eastward to the Arab world. To put it more precisely, an Arab astronomer, Ibn-Al-Haytham described the effects of pinhole and concave lenses in 1020. This was another significant step toward the invention of a telescope since the pinhole effect and concave lenses were essential knowledge for the creation of the first telescope.
Nevertheless, gradually, the development of optics as a science moved back to Europe, where developments of ancient scientists and Arabs were reconsidered and new inventions were made, such as “reading stones”ť (Born and Wolf, 1999), which were magnifying lenses placed on the reading material. In the 13-14th centuries, spectacles were invented in North Italy, with the invention of convex lenses. The invention of concave and convex lenses and their combination contributed to the use of lenses in spectacles, but, what was more important, people understood the basic principle of functioning and use of lenses, which were later applied to telescopes.
In fact, first telescopes were invented in the 17th century, but still it is possible to speak about devices which may be viewed as precursors of telescopes. Specialists (Elliott, 1966) point out that principles of telescopes were know in the late 16th century, but there are no physical evidence of telescopes in the pre-17th century period, but there were some documentary evidence, such as writings by John Dee and Thomas Digges in 1570 and 1571 respectively, who described the use of both reflective and refracting telescopes by Leonard Digges (Hecht, 2001).
However, the first practical exploitation of instrument which could be defined as a telescope was achieved only in 1608 in Netherlands. This invention was attributed to three different individuals, who claimed to be inventors, including Hans Lippershey, Jacob Metius and Jacob Adriaanszoon. The original Dutch telescopes were composed of a convex and a concave lenses and they did not invert the image. In this respect, the work of Galileo proved to be crucial for the improvement of the Dutch model of telescopes and it was Galileo who actually created the first telescope which laid the foundation to the construction of telescopes, similar in principle to modern ones. In this respect, it is worth mentioning the fact that Galileo used lenses which may be applied today as well (see table 1-3), but unlike the epoch of Galileo, today, an average person who has basic knowledge of optics can create a telescope using traditional design, similar to the one developed by Galileo (Graph 1), or even a simpler on (Graph 2).
At the same time, Europeans started to develop new telescopes, among which it is possible to single out refractive telescopes, which did not employ a tube at all. The objective was mounted on a pole and aimed by means of string. The eyepiece would be mounted on a stand at the focus and the image. However, such telescopes were inconvenient to use because of their size and quality. Later, such telescopes were improved along with the invention of reflecting telescope, which had a small convex hyperboloidal secondary mirror placed near the prime focus to reflect light through a central hole in the main mirror. After than no significant improvement in telescopes had been made until 1721, when John Hadley presented a Newtonian reflector with a metallic spectrum objective mirror of 6 inch aperture and 62 Âľ inch focal length (Hecht, 2001).
It is worth mentioning the fact that first telescopes suffered from chromatic errors. The first achromatic telescope was invented by Chester Moore Hall. He combined two lenses formed of different kinds of glass to make an achromatic lens where the effects of unequal retractions of two colors of light were corrected. The introduction of achromatic telescopes improved consistently telescopes and made findings made with the help of such telescopes more reliable than findings made with the help of conventional telescopes.
The 19th century did not bring any consistent breakthrough in the principle of construction of telescopes, but, instead, the 19th century became the epoch of giant optical telescopes, which grew in size and, thus, could be more effective than their predecessors. For instance, Lord Rosse’s telescope was 72 inches long (Born and Wolf, 1999). At the same time, as the science progressed, new technologies had started to be implemented in the construction of telescopes. The progress was particularly remarkable in the 20th century when absolutely new telescopes were invented and which revolutionized the construction of telescopes due to the use of new technologies.
In this respect, it is worth mentioning radio telescope, which was invented in the 1930s and it used radio emissions of space objects.
Remarkably all modern telescopes are reflectors. Later in the 20th century, Gamma-ray telescopes were invented, which used scintillation counters, spark chambers and solid-state detectors, but the angular resolution of these telescopes was poor. Furthermore, X-ray telescopes were built using nesting grazing-incidence mirrors, which deflected X-rays to a detector. In fact, an X-ray telescope is a high resolution gazing incidence telescope which is a successor to Yohkoh. The high resolution soft X-ray images would reveal magnetic field configuration and its evolution. One of the unique features of the X-ray telescope is its wide temperature coverage to see all the coronal features, that are not seen with any normal incidence telescope.Â The X-ray telescope consists of the X-ray and visible light optics, focal plane mechanism, and the 2k x 2k CCD camera
More recent inventions are ultra-violet telescopes which resemble optical telescopes but conventional aluminum-coated mirrors cannot be used and alternative coatings such as magnesium fluoride are used instead. Another recent invention is infra-red telescope. A modern ultraviolet imaging telescope is a 38 cm Ritchey-Chretien telescope equipped for ultraviolet filter and granting imagery over a 40 archminute field of view. It contains two detector systems: one in the far ultraviolet and another in the near ultraviolet. Images are recorded on 70 mm film.
At the same time, the development of modern telescopes does not only contributes to the creation of new, extremely sophisticated telescopes which are used by leading scientists. In fact, today, telescopes have become available to large masses of people who are interested in astronomy. In actuality, amateur astronomers can choose from a wide assortment of telescope types and manufacturers. There is no one telescope for all skies, eyes and celestial studies, issues of field flatness, and hefty optical tubes.
On analyzing current trends in the development of telescopes, it should be said that modern telescopes become more and more sophisticated. At the same time, the development of modern telescopes is grounded on the introduction of new technologies, including information technologies. On the other hand, the development of new technologies allowed to modernize conventional telescopes and improve consistently. In this respect, it is worth mentioning a digital telescope which actually represents a conventional telescope that incorporates digital electronics ”“ electronics system that use digital signals, instead of aiming a telescope manually. In such a way, a computer can assist astronomers that makes their work easier and more effective.
Thus, taking into account all above mentioned, it is possible to conclude that the history of telescope mirrors the development of technologies from the beginning of optics to the development of extremely sophisticated devices built on the ground of the latest technological advancements in different fields of science. On analyzing the history of telescopes, it is important to lay emphasis on the fact that people were always interested in the research of the space and universe. However, at the dawn of the development of telescopes history, it was a serious challenge to conventional cultural and religious norms. On the other hand, the invention of telescopes revolutionized science and contributed to the emergence of absolutely new branches of science such as astronomy, astrophysics, and many others. Today, it is practically impossible to imagine the world without telescopes. Telescopes perform an extremely important function since they applied to the research of the outer space.
It is hardly possible to underestimate the contribution of telescopes to the development of modern astronomy and to the understanding of the universe and its origin and formation, as well as the origin and development of planets and stars. In fact, modern telescopes provide astronomers with opportunities which they could have dreamed about for decades without a hope to obtain such advanced telescopes as modern ones. On the other hand, it is obvious that the development of modern telescopes heavily relies on the historical development of telescopes since without experiments and findings of scientists in the past, it would be impossible to create modern, sophisticated telescopes.
Furthermore, it is alsoÂ important to point out the fact that the modern development of telescopes involves technological developments not only in the field of optics solely, but also in many other fields of science, including physics and even information technologies. In such a way, modern telescopes become highly technological devices which incorporate the most advanced technologies and progressive ideas of specialists working in different fields of science.
Within a few centuries, telescopes and optics have made a huge progress. The technological difference between first telescopes and modern ones is really impressing. In fact, modern telescopes can reach distance unimaginable to human mind at the epoch when first telescopes were created. At the same time, the modern science keeps progressing and new telescopes, more advanced technologically, appear and, now, it is hardly possible to imagine what a kind of telescope people will use in a century or even in a few decades.