The first telescopes and their inventors. The history of the creation of the telescope. The main historical milestones are the invention of telescopes. Schematic diagram of the telescope

Ministry of Education of the Orenburg Region

State Educational Institution of Primary Vocational Education Vocational School - No. 17

SUMMARY ON THE TOPIC:

"Telescopes and the history of their creation"

1st year student #2

Podkopaev Eduard

Supervisor:

Obukhova N.S.

Abdulino, 2010

Introduction………………………………………………………………….2

1.1 The history of the creation of the first telescopes……………………………….5

1.2.Modern types of telescopes ……………………..…………….8

2. Chapter 2…………………………………………………………………….12

2.1 Home telescope………………………………………………..12

Conclusion…………………………………………………..…………13

List of used literature…………………………………………………………14

Applications……………………………………………………………..15

Introduction

After all, every day the sun walks before us,

However, the stubborn Galileo is right.

A.S. Pushkin

Telescope (from other Greek τῆλε - far + σκοπέω - I look) - a device designed to observe celestial bodies. Indeed, this optical device is a powerful spotting scope designed to observe very distant objects - celestial bodies.

There are telescopes for all ranges of the electromagnetic spectrum: optical telescopes, radio telescopes, x-ray telescopes, gamma-ray telescopes. In addition, neutrino detectors are often referred to as neutrino telescopes. Also, gravitational wave detectors can be called telescopes.

Optical telescopic systems are used in astronomy (for observing celestial bodies, in optics for various auxiliary purposes: for example, to change the divergence laser radiation. Also, the telescope can be used as a spotting scope to solve problems of observing distant objects.

Relevance: created about four hundred years ago, the telescope is a kind of symbol modern science, embodying the eternal desire of mankind for knowledge.

Object of study: different types of telescopes.

Target our study to consider the history of the creation of the telescope, to create a home telescope.

Tasks research: collect and study theoretical material about the telescope, using all available sources of information.

The main hypothesis is telescopes and grandiose observatories make a significant contribution to the development of entire areas of science devoted to the study of the structure and laws of our universe.

Scientific novelty of our work lies in the importance of telescopes at the present stage of development of science and technology (in the history of space)

Practical significance: research materials can be used in the lessons of physics, history, geography, in extracurricular activities. Today, more and more often a telescope can be found not in a scientific observatory, but in an ordinary city apartment, where an ordinary amateur astronomer lives, who goes on clear starry nights to join the breathtaking beauties of space.

Chapter 1

1.1. The history of the creation of the first telescopes

It is difficult to say who first invented the telescope. The year of the invention of the telescope, or rather the telescope, is considered to be 1608, when the Dutch spectacle master John Lippershey demonstrated his invention in The Hague. Nevertheless, he was denied a patent, due to the fact that other masters, like Zachary Jansen from Middelburg and Jakob Metius from Alkmaar, already possessed copies of telescopes, and the latter, shortly after Lippershey, submitted a request to the States General (Dutch Parliament) for patent. Later research showed that spyglasses were probably known earlier, as early as 1605, in the "Additions to Vitellia", published in 1604. Kepler considered the path of rays in an optical system consisting of a biconvex and biconcave lenses. The very first drawings of the simplest lens telescope (both single-lens and two-lens) were discovered in the notes of Leonardo da Vinci dating back to 1509. His entry has been preserved: “He made glasses to look at full moon” (“Atlantic Code”). (2,136)

It is known that even the ancients used magnifying glasses. A legend has come down to us that, allegedly, Julius Caesar, during a raid on Britain from the shores of Gaul, examined the foggy British land through a spyglass. Roger Bacon, one of the most remarkable scientists and thinkers of the 13th century, claimed in one of his treatises that he had invented a combination of lenses by which distant objects at a distance appear close. (1, 46)

Whether this was actually the case is unknown. It is indisputable, however, that at the very beginning of the 17th century in Holland, almost simultaneously, three opticians announced the invention of the telescope: Lieperschey, Meunus, Jansen. Be that as it may, by the end of 1608 the first spyglasses were made and rumors about these new optical instruments quickly spread throughout Europe.

In Padua at that time, Galileo Galilei, a professor at the local university, an eloquent orator and a passionate supporter of the teachings of Copernicus, was already widely known. Hearing about a new optical instrument, Galileo decided to build a telescope with his own hands. January 7, 1610 will forever remain a memorable date in the history of mankind. On the evening of the same day, Galileo pointed the telescope he built for the first time into the sky. (Appendix No. 1.Fig. 1)

He saw what was previously impossible. The moon, dotted with mountains and valleys, turned out to be a world similar at least in relief to the Earth. Jupiter appeared before the eyes of the astonished Galileo as a tiny disk, around which four unusual stars revolved - its satellites. When observed through a telescope, the planet Venus turned out to be like a small moon. It changed its phases, which testified to its circulation around the Sun. On the Sun itself (placing dark glass before his eyes), the scientist saw black spots, thereby refuting the generally accepted teaching of Aristotle about the "inviolable purity of heaven." These spots were displaced in relation to the edge of the Sun, from which he made the correct conclusion about the rotation of the Sun around its axis. On dark nights, when the sky was clear, many stars were visible in the field of view of the Galilean telescope, inaccessible to the naked eye. The imperfection of the first telescope did not allow the scientist to see the ring of Saturn. Instead of a ring, he saw two strange appendages on both sides of Saturn. Galileo's discoveries marked the beginning of telescopic astronomy. But his telescopes, which finally approved the worldview of Copernicus, were very imperfect. Already during the life of Galileo, telescopes of a slightly different type came to replace them. The inventor of the new tool was Johannes Kepler. (Appendix No. 1.Fig. 2)

In 1611, in his treatise Dioptrics, he gave a description of a telescope consisting of two biconvex lenses. Kepler himself, being a typical theoretical astronomer, limited himself to only describing the scheme of the new telescope, and the first to build it was Scheiner, Galileo's opponent in their heated debate. By 1656, Christian Huyens made a telescope that magnified 100 times the observed objects, its size was more than 7 meters, the aperture was about 150 mm. This telescope is already considered to be at the level of today's amateur telescopes for beginners. By the 1670s, a 45-meter telescope had already been built, which further enlarged objects and gave a greater angle of view. But even an ordinary wind could serve as an obstacle to obtaining a clear and high-quality image. (Appendix No. 2)

Isaac Newton at that time managed to give new life to telescopes with the help of a mirror. He made the first mirror for a telescope with a diameter of 30 mm from an alloy of copper, tin and arsenic in 1704. The image became clear.

The two-mirror system in a telescope was proposed by the Frenchman Cassegrain. Cassegrain could not realize his idea in full due to the lack of technical feasibility of inventing the necessary mirrors, but today his drawings have been implemented. It is Newton's and Cassegrain's telescopes that are considered the first "modern" telescopes, invented at the end of the 19th century. By the way, the Hubble Space Telescope works just like the Cassegrain telescope. And Newton's fundamental principle using a single concave mirror has been used at the Special Astrophysical Observatory in Russia since 1974.

I'M IN. Bruce became famous for developing special metal mirrors for telescopes. Lomonosov and Herschel, independently of each other, invented a completely new design of the telescope, in which the primary mirror tilts without the secondary one, thereby reducing light loss. And Herschel himself in the workshop fused mirrors made of copper and tin. The main work of his life is a large telescope with a mirror with a diameter of 122 cm. (Appendix No. 3. Figs 1 and 2).

By the end of the 18th century, compact, handy telescopes had replaced bulky reflectors. Metal mirrors also turned out to be not very practical - expensive to manufacture, as well as dimming with time.

By 1758, with the invention of two new types of glass: light - crowns and heavy - flint, it became possible to create two-lens lenses. This was successfully used by the scientist J. Dollond, who made a two-lens lens, later called the dollar lens. (Appendix 4).

The German optician Fraunhofer put the production and quality of lenses on the conveyor. And today there is a telescope with a whole, working Fraunhofer lens in the Tartu Observatory. But the refractors of German optics were also not without a flaw - chromatism. (Annex 5)

1. THE INVENTION OF THE TELESCOPE BY GALILEO

In the spring of 1609, a professor of mathematics at the University of the Italian city of Padua learned that a Dutchman had invented an amazing pipe. Distant objects, when viewed through it, seemed closer. Taking a piece of a lead pipe, the professor inserted two glasses into it from both ends: one is plano-convex, and the other is plano-concave. “Letting my eye against a plano-concave lens, I saw objects large and close, as they seemed to be one third of the distance compared to observation with the naked eye,” wrote Galileo Galilei.

The professor decided to show his instrument to his friends in Venice. “Many noble people and senators climbed the highest bell towers of the churches of Venice to see the sails of the approaching ships, which were so far away that they needed two hours of full speed to be noticed by the eye without my spotting scope,” he reported.

Of course, Galileo had predecessors in the invention of the telescope (from the Greek "tele" - "far", "far" and "skopeo" - "look"). Legends have been preserved about the children of a spectacle master, who, playing with lenses that collect and scatter light, suddenly discovered that, at a certain location relative to each other, two lenses can form a magnifying system. There is information about spotting scopes made and sold in Holland before 1609. Main Feature Galilean telescope was its high quality. Convinced of the poor quality of spectacle lenses, Galileo began to grind the lenses himself. Some of them have survived to this day; their study showed that they are perfect from the point of view of modern optics. True, Galileo had to choose: it is known, for example, that after processing 300 lenses, he selected only a few of them for telescopes.

However, the difficulty of making first-class lenses was not the biggest obstacle to building a telescope. According to many scientists of that time, Galileo's telescope could be considered as a diabolical invention, and its author should have been sent for interrogation to the Inquisition. After all, people see because, they thought, visual rays come out of the eyes, feeling the entire space around. When these rays hit an object, its image appears in the eye. If, however, a lens is placed in front of the eye, then the visual rays will be bent and the person will see something that is not really there.

Thus, the official science of the times of Galileo could well consider the luminaries and distant objects visible in the telescope to be a game of the mind. The scientist understood all this well and struck the first blow. The demonstration of a telescope with which it was possible to detect distant ships invisible to the eye convinced all the doubters, and Galileo's telescope spread at lightning speed across Europe.

2. TELESCOPES OF HEVELIUS, HUYGENS, KEPLER AND THE PARIS OBSERVATORY

The son of a wealthy citizen of the Polish city of Gdansk, Jan Hevelius, has been involved in astronomy since childhood. In 1641 he built an observatory, where he worked with his wife Elizabeth and assistants. Hevelius took the next step in improving the spotting scopes.

Galileo's telescopes had a significant drawback. The refractive index of glass depends on the wavelength: red rays are deflected by it more weakly than green ones, and green rays are weaker than violet ones. Consequently, a simple lens, even of impeccable quality, has a greater focal length for red rays than for violet ones. The observer will focus the image in blue-green rays, to which the eye is most sensitive at night. As a result, bright stars will look like blue-green dots surrounded by red and blue borders. This phenomenon is called chromatic aberration; of course, it greatly interferes with the observation of stars, the moon and planets.

Theory and experience have shown that the effect of chromatic aberration can be reduced by using a lens with a very long focal length as a lens. Hevelius started with lenses with a 20-meter focus, and his longest telescope had a focal length of about 50 m. The lens was connected to the eyepiece by four wooden planks, into which many diaphragms were inserted, making the structure more rigid and protecting the eyepiece from extraneous light. All this was suspended with a system of ropes on a high pole, the telescope was aimed at the desired point in the sky with the help of several people, apparently retired sailors familiar with the maintenance of mobile ship gear.

Hevelius did not make lenses himself, but bought them from a Warsaw master. They were so perfect that in a calm atmosphere it was possible to see diffraction images of stars. The fact is that even the most perfect lens cannot build an image of a star in the form of a point. Due to the wave nature of light in a telescope with good optics, the star looks like a small disk surrounded by bright rings of decreasing brightness. Such an image is called diffraction. If the telescope optics are imperfect or the atmosphere is restless, the diffraction pattern is no longer visible: the star appears to the observer as a spot, the size of which is larger than the diffraction pattern. Such an image is called an atmospheric disk.

Dutch astronomers brothers Christian and Constantine Huygens built Galilean telescopes in their own way. The lens, mounted on a ball joint, was placed on a pole and could be set at the desired height using a special device. The optical axis of the objective was directed to the object under study by the observer, who turned it with the help of a strong cord. The eyepiece was mounted on a tripod.

On March 25, 1655, Christian Huygens discovered Titan, the brightest satellite of Saturn, and also saw the shadow of the rings on the planet's disk and began studying the rings themselves, although at that time they were observed edge-on. “In 1656,” he wrote, “I was able to look through the telescope at the middle star of the Sword of Orion. Instead of one, I saw twelve, three of them almost touching each other, and four others shining through the nebula, so that the space around them seemed much brighter than the rest of the sky, which seemed completely black. It was as if there was a hole in the sky through which a brighter area is visible. Huygens polished the lenses himself, and his "air tube" turned out to be a step forward compared to the "long tubes" of Hevelius. The eyepiece he invented is easy to make and is still in use today.

The high level of skill laid down by Galileo contributed to the flourishing of the Italian optical school. At the end of the XVII century. the Paris Observatory was under construction; it was equipped with several telescopes of the Galilean system. With the help of two such instruments and a 40-meter telescope, its first director, the Italian Giovanni Domenico Cassini, discovered four new satellites of Saturn and studied the rotation of the Sun.

The brilliant German astronomer Johannes Kepler received Galileo's telescope for a short time from a friend. He instantly realized what advantages this device would gain if the diverging lens of the eyepiece was replaced with a converging one. The Keplerian telescope, which, unlike Galileo's, gives an inverted image, is used everywhere to this day.

3. Newton-Herschel reflectors

The main drawback of the Galilean tubes - chromatic aberration - undertook to eliminate Isaac Newton. At first, he wanted to use two lenses as a lens - positive and negative, which would have different optical power, but chromatic aberration of the opposite sign. Newton tried several options and came to the erroneous conclusion that it was impossible to create an achromatic lens objective. (True, contemporaries testify that he carried out these experiments in a great hurry).

Then Newton decided to do away with this problem radically. He knew that an achromatic image of distant objects builds a concave mirror on its axis, made in the form of a paraboloid of revolution. Attempts to construct reflecting telescopes were already made at that time, but they were not crowned with success. The reason was that in the two-mirror scheme used before Newton, the geometric characteristics of both mirrors must be strictly consistent. And this is exactly what opticians could not achieve.

Telescopes in which a mirror acts as a lens are called reflectors (from lat. reflectere - “reflect”), in contrast to telescopes with lens lenses - refractors (from lat. refractus - “refracted”). Newton made his first reflector with a single concave mirror. Another small flat mirror directed the constructed image to the side, where the observer viewed it through the eyepiece. The scientist made this instrument with his own hands in 1668. The length of the telescope was about 15 cm. “Comparing it with a good Galilean tube 120 cm long,” Newton wrote, “I could read at a greater distance with my telescope, although the image was less bright.

Newton not only polished the mirror of the first reflector, but also developed a recipe for the so-called mirror bronze, from which he cast the mirror blank. In ordinary bronze (an alloy of copper and tin), he added a certain amount of arsenic: this improved the reflection of light; in addition, the surface is lighter and better polished. In 1672, the Frenchman, teacher of the provincial lyceum (according to other sources, the architect) Cassegrain proposed the configuration of a two-mirror system, the first mirror in which was parabolic, while the second had the shape of a convex hyperboloid of revolution and was located coaxially in front of the focus of the first. This configuration is very convenient and is now widely used, only the main mirror has become hyperbolic. But at that time, they could not make a Cassegrain telescope due to the difficulties associated with achieving the desired mirror shape.

Compact, easy-to-handle high-quality reflectors with metal mirrors by the middle of the 18th century. supplanted the "long pipes", enriching astronomy with many discoveries. At that time the Hanoverian dynasty was called to the English throne; his compatriots, the Germans, rushed to the new king. One of them was William Herschel, a musician and at the same time a talented astronomer.

Convinced of how difficult it was to handle the Galilean tubes, Herschel moved on to reflectors. He himself cast blanks from mirror bronze, ground and polished them himself; his optical machine has survived to this day. Brother Alexander and sister Caroline helped him in his work; she recalled that their entire house, including the bedroom, was turned into a workshop. Using one of his telescopes, Herschel discovered in 1778 the seventh planet in the solar system, later named Uranus.

Herschel continuously built more and more reflectors. The king patronized him and gave him money for the construction of a huge reflector with a diameter of 120 cm with a pipe 12 m long. After many years of effort, the telescope was completed. However, it proved difficult to work with, and in terms of its qualities it did not surpass smaller telescopes as significantly as Herschel had assumed. Thus was born the first commandment of telescope builders: "Don't make big leaps."

4. SINGLE LENS LONG REFRACTORS

Single-lens long refractors reached in the 17th century. conceivable limits of perfection; astronomers learned how to select high-quality glass blanks for their lenses, precisely process and mount them. The theory of the passage of light through optical details was developed (Descartes, Huygens).

Without exaggeration, we can say that the creation of modern large reflectors is firmly on the ground laid down in the 17th - 18th centuries. foundation. The modified Cassegrain configuration is implemented in all modern night telescopes without exception. The art of working with metal mirrors, the permissible deflection of which at any position of the telescope should not exceed small fractions of a micrometer, eventually led to the creation of highly advanced computer-controlled mirror frames for giant telescopes. The optical schemes of some eyepieces of that time are still used today. Finally, it was then that the beginnings of scientific methods for studying the shape of the surfaces of optical elements appeared, which today have crystallized into a complete scientific discipline - the technology of manufacturing large-scale optics.

5. REFRACTORS OF THE 19TH CENTURY

It took about a century to be convinced of the fallacy of Newton's statement that it was impossible to create an achromatic lens. In 1729, a lens was made from two lenses of different glass, which made it possible to reduce chromatic aberration. And in 1747, the great mathematician Leonhard Euler calculated a lens consisting of two glass menisci (optical glass, convex on one side and concave on the other), the space between which is filled with water - just like in Jules Verne's Mysterious Island. He had to build images devoid of a color border. The English optician John Dollond, together with his son Peter, undertook a series of experiments with prisms from Venetian glass known since the time of Galileo (crown) and a new English type of glass - flint glass, which had a strong luster and was used to make jewelry and glasses. It turned out that from these two varieties it is possible to make a lens that does not give a color border: a positive lens should be made from a crown, and a slightly weaker negative lens from a flint glass. Mass production of Dollon pipes began.

All of Europe was engaged in achromatic telescopes. Euler, D "Alembert, Clairaut and Gauss continued their calculation; several London opticians challenged the patent for an achromatic lens taken by the Dollons in court, but did not achieve success. Peter Dollond already developed a three-lens achromat, according to astronomers, very good; Jesuit professor Ruger Boshko Vich in Padua came up with a special device - a vitrometer (from Latin vitrum - "glass") for exact definition refractive indices of optical glasses. In 1780, the Dollonds began mass production of several types of military collapsible telescope. When John Dollond married his daughter (of course, to an optician), her dowry was part of a patent for an achromatic lens.

The scientific method of making lens lenses was put into practice by the German optician Josef Fraunhofer. He established the control of lens surfaces using the so-called Newton's color rings, developed mechanical devices for lens control (spherometers) and analyzed Dollond's calculations. He began to measure the refractive indices with the light of a sodium lamp and at the same time studied the spectrum of the Sun, finding in it many dark lines, which are still called Fraunhofer lines.

Fraunhofer's 24 cm lens for the Dorpt refractor (Dorpt - formerly Yuryev, now Tartu, Estonia) was perfectly corrected for chromatic and spherical aberrations; this telescope for a long time remained the largest in the world. The installation of the telescope in Dorpat was carried out under the direction of Vasily Struve (later the founder and director of the Pulkovo Observatory).

The Derpt refractor turned out to be an incredibly successful device. With its help, Struve measured the distance to the brightest star northern hemisphere sky - Vega; it turned out to be huge: about 26 light years. The design of this telescope was repeated throughout the 19th century; small telescopes are made after his model even now.

6. FIRST GENERATION TELESCOPES

By the middle of the XIX century. The Fraunhofer refractor became the main instrument of observational astronomy. The high quality of optics, convenient mounting, a clockwork mechanism that allows you to keep the telescope constantly pointed at the star, stability, and the absence of the need to constantly adjust and adjust something have won the deserved recognition of even the most demanding observers. It would seem that the future of refractors should be cloudless. However, the most astute astronomers have already understood their three main shortcomings: this is still noticeable chromatism, the impossibility of making a lens of a very large diameter, and a rather significant length of the tube compared to a Cassegrain reflector of the same focus.

Chromatism has become more noticeable because the spectral region in which studies of celestial objects have been expanded has expanded. The photographic plates of those years were sensitive to violet and ultraviolet rays and did not feel visible to the eye blue-green area, for which the lenses of the refractors were achromatized. It was necessary to build double telescopes, in which one tube carried a lens for photographic observations, the other for visual ones.

In addition, the refractor lens worked with its entire surface, and, unlike a mirror, it was impossible to bring levers under it from the back side to reduce its deflection, and on mirror telescopes such levers (unloading system) were used from the very beginning. Therefore, the refractors stopped at a diameter of about 1 m, and the reflectors later reached 6 m, and this is not the limit.

As always, the development of technology contributed to the emergence of new reflectors. In the middle of the 19th century, the German chemist Justus Liebig proposed a simple chemical method silvering of glass surfaces This made it possible to manufacture glass mirrors. It polishes better than metal, and is much lighter than it. Glassmakers also improved their methods, and it was safe to talk about blanks with a diameter of about 1 m.

It remained to develop a scientifically based method for controlling concave mirrors, which he did in the late 50s. 19th century French physicist Jean Bernard Léon Foucault, inventor of the well-known pendulum. He placed a point source of light at the center of the curvature of the spherical mirror being tested and blocked its image with a knife. By looking at which side a shadow appears on the mirror when the knife moves perpendicular to the axis of the mirror, you can set the knife exactly in focus, and then very clearly see the inhomogeneities and surface errors. Refractors can also be studied by this method: a star serves as a point source. Sensitive and visual, the Foucault method is used today by both amateurs and professionals.

Foucault made two telescopes with a tube length of 3.3 m and a diameter of 80 cm according to his method. It became clear that Fraunhofer refractors had a formidable competitor.

In 1879 in England, the optician Common made a concave glass parabolic mirror with a diameter of 91 cm. Scientific control methods were used in its manufacture. The mirror was acquired by a wealthy amateur astronomer, Crossley, who mounted it in a telescope. However, this tool did not suit its owner, and in 1894 Crossley announced its sale. The Lick Observatory, organized in California, agreed to buy it, albeit for free.

Crossley reflector hit good hands. Astronomers sought to get the most out of him: the new telescope was used to photograph astronomical objects; with its help, many previously unknown extragalactic nebulae were discovered, similar to the Andromeda nebula, but of a smaller angular size. The glass reflector of the first generation proved to be effective.

The next telescope of this type was built on American soil - also in California, at the newly created Mount Wilson Solar Observatory. A blank for a mirror with a diameter of 1.5 m was cast in France; its processing was carried out at the observatory, and the mechanical parts were ordered from the nearest railway depot.

As can be seen from the documents, one person bore full responsibility for the new telescope - the optician George Ritchie. He was, in modern terms, the chief designer of this device. The main improvements were a very good clockwork, a new bearing system, a device for quickly moving the photo cassette in two directions, and measures to equalize the temperature near the main mirror to prevent its shape from being distorted due to thermal expansion. Richie photographed the sky himself; the exposure time reached 20 hours (for the day, the cassette with the photographic plate was removed into a dark room).

The results were not long in coming: Richie's magnificent pictures are still published in textbooks and popular publications.

The next, already 2.5-meter reflector, began working at Mount Wilson in 1918. All the improvements of the predecessor and the experience of its operation were used in the design of a gigantic instrument at that time.

The new telescope was more efficient than the previous one in the sense that on it an ordinary astronomer, not experienced in handling telescopes, could easily photograph the same faint stars that were obtained on a 1.5-meter one as a record. And in the hands of a master of its craft, this telescope made a world-class discovery. At the beginning of the XX century. the distance to the nearest galaxies was for astronomers the same mystery as the distance from the Earth to the Sun at the beginning of the 17th century. There are works in which it was stated that the Andromeda Nebula is located in our Galaxy. The theorists were prudently silent; meanwhile, a reliable method had already been developed for determining the distances to distant stellar systems from variable stars.

In the autumn of 1923, the first variable star of the required type, the Cepheid, was discovered in the Andromeda Nebula. Soon their number increased to ten in different galaxies. It was possible to determine the periods of these variables, and from them the distances to other galaxies.

Measuring the distances to several extragalactic nebulae made it possible to establish that the farther away a galaxy is, the faster it moves away from us.

1.5- and 2.5-meter reflectors have long served faithfully in observational astronomy; they are now decommissioned due to sky glare from the Los Angeles metropolitan area.

Let us list the main features of modern first-generation telescopes.

First, their main mirrors have a strictly parabolic shape. They are made of glass of the mirror type with a significant coefficient of thermal expansion (which is a disadvantage, since the shape of the mirror is distorted due to the uneven temperature of its various parts) and look like a solid cylinder with a thickness to diameter ratio of approximately 1:7.

Secondly, the design of their pipe is made according to the principle of maximum rigidity. The main and secondary mirrors fixed in it must be on the same axis within the error limits specified in the calculation of the optics. If this is not the case, then the quality of the telescope will inevitably deteriorate, therefore the design of the telescope tube is calculated so that in any position the bending of the tube is less than the tolerance specified by the optics. Naturally, such a pipe is quite massive. Telescope bearings - sliding or ball bearings. In the first two telescopes, the load on them is reduced by floats, on which the telescope almost floats in mercury baths.

7. CREATION OF SECOND GENERATION TELESCOPES

So, the 2.5-meter telescope started working and gave excellent results. scientific results, and the team around him at Mount Wilson Observatory boldly looked to the future and discussed the possibility of building a larger instrument. At the same time, they called a diameter of 5 and even 7.5 m. The merit of the head of the observatory, J. Hale, is that he saved his employees from unnecessary striving for ever larger sizes and limited the diameter of the new device to five meters. In addition, he got (and this in the conditions of the impending economic crisis of 1929-1933) a significant amount, which made it possible to start work.

It was impossible to make a mirror solid: in this case, its mass would be 40 tons, which would make the structure of the tube and other parts of the telescope excessively heavy. It also could not be made of mirror glass, because observers had already suffered with such mirrors: when the weather changed and even when day and night changed, the shape of the mirror was distorted, and it “recovered” extremely slowly. The designers wanted to make a mirror from quartz, whose thermal expansion coefficient is 15 times less than that of glass, but this was not possible.

I settled on Pyrex, a type of heat-resistant glass designed to make transparent frying pans and pots. The gain in the expansion coefficient was 2.5 times. In 1936, on the second attempt, the mirror was cast; on the back side, it had a ribbed structure, which lightened the weight up to 15 tons and improved heat transfer conditions. The processing of the mirror was carried out at the observatory; during the Second World War, it was suspended and ended in 1947. At the end of 1949, the 5-meter telescope was put into operation.

As in the first generation of reflectors, the shape of its main mirror was parabolic, observations could be made in Newtonian, Cassegrain, direct or broken foci. The latter does not move when the telescope moves, and it can accommodate heavy stationary equipment, such as a large spectrograph.

Fundamental changes were made to the design of the 5-meter reflector pipe: it was no longer rigid. Engineers allowed its ends to bend relative to the center, provided that the optical parts did not move relative to each other. The design turned out to be successful and is still used in all night telescopes without exception.

I also had to change the design of the bearings of the telescope. 5-meter telescope "floats" on thin layer oil injected by the compressor into the space between the axle and its bearings. Such a system has no static friction and allows the tool to rotate accurately and smoothly.

One of the most important results of the work of the 5-meter reflector of the Mount Wilson Observatory was a reliable proof of the fact that the source of energy for stars is thermonuclear reactions in their depths. This information explosion in the field of galaxy research is also largely due to the observations with this telescope.

Numerous second-generation telescopes were made; a characteristic representative of them is a reflector with a diameter of 2.6 m of the Crimean Observatory.

A few words about telescope construction in our country. In the 30s. there was effective cooperation between astronomers and telescope builders, but they were not united at any observatory - this happened later. It was planned to manufacture an 81 cm refractor, reflectors with a diameter of 100 and 150 cm and numerous auxiliary equipment. The Great Patriotic War prevented the full implementation of this program, and the first series of telescopes of small diameter (up to 1 m) appeared in the USSR only in the 1950s. Then two reflectors with a diameter of 2.6 m and a 6-meter telescope were built. Practically in all the southern republics of the USSR, new observatories were created or the observatories that already existed there were significantly developed.

8. DEVELOPMENT OF REFLECTORS OF THE THIRD AND FOURTH GENERATIONS

The work on reflectors of the second generation showed that a 3-meter telescope with high-quality optics, installed in a point with a calm atmosphere, can be more efficient than a 5-meter telescope operating in poorer conditions. This was taken into account when developing reflectors of the third generation.

The construction of a new telescope differs from the work on the creation of other types of equipment. A modern aircraft has been tested for many years in the form of prototypes and only then goes into mass production. Now a large telescope costs about the same as an airplane, but astronomers, unfortunately, do not have the money for a prototype. It is replaced by careful study of available tools and frequent project discussions. Usually one or two instruments in the series are built first; the experience gained in doing so is extremely valuable. If the instrument is very large and expensive, a smaller prototype is still being built.

The main feature of the third generation telescopes is the main mirror with a diameter of 3.5 - 4 m of hyperbolic (rather than parabolic) shape, made of new materials: fused quartz or glass ceramics - glass ceramics with almost zero thermal expansion, developed in the USSR in the 60s . The use of the main hyperbolic mirror in the Cassegrain configuration makes it possible to significantly expand the field of good images; This system was calculated in the 1920s. Telescopes of the third generation tend to be installed in places specially chosen for the calmness of the atmosphere. Quite a lot of such telescopes have now been built; it is considered to be a university grade instrument.

The 6-meter telescope, commissioned in 1975, although it belongs to the second generation, one cardinal change was made to its design. Telescopes of previous generations were installed equatorially. They accompanied the observed star, turning at the speed of one revolution per sidereal day around the axis directed to the celestial pole. According to the second coordinate of the object - declination - the telescope is set before photographing begins and does not rotate around this axis anymore.

Even before the Second World War, the domestic designer of astronomical instruments N.G. Ponomarev drew attention to the fact that the telescope tube and its entire structure would be much lighter, and therefore cheaper, if we switch from an equatorial to an azimuthal installation, that is, if the telescope rotates around three axes - the azimuth axis, the altitude axis and optical axis (only the cassette with a photographic plate can be rotated there). This idea was implemented in a 6-meter telescope, called BTA (Large Azimuth Telescope). It is installed in the astrophysical observatory in the North Caucasus, near the village of Zelenchukskaya.

An azimuthal mount is used in all fourth-generation telescopes without exception. In addition to this innovation, they are characterized by an exceptionally thin mirror, the shape of which is adjusted by a computer after an automatic analysis of the optical system according to the image of the star. More than ten instruments of this type with a diameter of more than 8 m are being built, and their model with a diameter of 4 m is already in operation. It is even difficult to imagine what new discoveries they will bring to astronomy.

9. EMISSION AND IMAGE DETECTORS

No matter how complex a system of a telescope, light filters, interferometers and spectrographs astronomers build, at its output there is inevitably a radiation or image receiver. The image receiver registers the image of the source. The radiation receiver registers only the intensity of the radiation, saying nothing about the shape and size of the object that illuminates it.

The first image receiver in astronomy was the naked human eye. The second was a photographic plate. For the needs of astronomers, photographic plates were developed that are sensitive in various regions of the spectrum, up to infrared and, most importantly, work well when observing faint objects. An astronomical photographic plate is an exceptionally capacious, cheap and durable storage medium; many of the images have been kept in the glass libraries of the observatories for more than a hundred years. The largest photographic plate is used on one of the telescopes of the third generation: its size is 53 x 53 cm!

In the early 30s. Leningrad physicist Leonid Kubetsky invented a device later called a photomultiplier tube (PMT). Light from a weak source falls on a light-sensitive layer deposited inside a vacuum flask and knocks out electrons from it, which are accelerated by an electric field and fall on plates that multiply their number. One electron knocks out three or five electrons, which in turn multiply on the next plate, and so on. There are about ten such plates, so the amplification is enormous. Photomultipliers are produced industrial way and are widely used in nuclear physics, chemistry, biology and astronomy. The work on the study of stellar energy sources has been done largely with the help of the PMT - this simple, accurate and stable instrument.

Almost simultaneously with the photomultiplier in different countries the inventors independently created an image intensifier tube (IOC). It is used in night vision devices, and specially designed high-quality devices of this type are effectively used in astronomy. The image intensifier tube also consists of a vacuum flask, at one end of which there is a light-sensitive layer (photocathode), and at the other - a luminous screen, similar to a television one. An electron knocked out by light is accelerated and focused on a screen glowing under its action. In modern image intensifier tubes, an electron image intensifying plate is inserted, made up of many microscopic photomultipliers.

In recent years, the so-called charge-coupled devices (CCDs) have become widely used in astronomy, and they have already won a place in transmitting television cameras and portable video cameras. Light quanta here release charges, which, without leaving a specially treated plate of crystalline silicon, accumulate under the action of applied voltages in its certain places - image elements. By manipulating these voltages, it is possible to move the accumulated charges in such a way as to direct them sequentially, one at a time, to the processing complex. Images are reproduced and processed using a computer.

CCD systems are very sensitive and can measure light with high precision. The largest instruments of this kind do not exceed the size of a postage stamp, but nevertheless they are effectively used in modern astronomy. Their sensitivity is close to the absolute limit set by nature; good CCDs can register "by the piece" most light quanta falling on them.

BIBLIOGRAPHY

telescope galileo reflector

1. Mikhelson N.N. Optical telescopes: Theory and design. -- M.: Nauka, 1976.

2. Maksutov D.D. Astronomical optics - M.: Nauka, 1979.

3. Navashin M.S. Amateur astronomer's telescope. -- 4th ed. -- M.: Nauka, 1979.

4. Amateur telescopes. Sat. articles / Ed. MM. Shemyakin. -- M.: Nauka, 1975.

5. Maksutov D.D. Optical planes, their research and production. - L., 1934.

6. Melnikoe O.A., Slyusarev G.G., Markov A.V., Kuprevich N.F. modern telescope. -- M.: Nauka, 1975.

7. Sulim A.V. Manufacture of optical parts. -- 2nd ed., Supplementary. -- M.: Higher school, 1969.

2. Features of astronomical observations

Astronomy is based on observations made from the Earth and only since the 60s of our century, also carried out from space - from automatic and manned stations. Observations in astronomy, playing the same role as experiments in physics and chemistry, have a number of features.

First Feature consists in the fact that astronomical observations are in most cases passive in relation to the objects under study. We cannot actively influence celestial bodies, perform experiments (with the exception of rare cases), as is done in other natural sciences. Only the use of spacecraft made it possible to conduct direct research on the Moon and the nearest planets.

In addition, many celestial phenomena proceed so slowly that their observation requires enormous periods; for example, a change in the inclination of the earth's axis to the plane of its orbit becomes clearly visible only after hundreds of years. Therefore, for us, some observations made thousands of years ago have not lost their significance, although they were, according to modern concepts, very inaccurate.

Second feature. We observe the position of celestial bodies and their movement from the Earth, which itself is in motion - rotates around its axis and revolves around the Sun. However, when describing the motion of celestial bodies in relation to the earthly observer, we often consider it to be motionless. For example, we are talking about the rising and setting of the luminaries, although it is known that this occurs due to the rotation of the Earth, about the annual movement of the Sun through the constellations, although it is a consequence of the revolution of the Earth around the Sun. In addition, due to the movement of the Earth, the view of the sky for an earthly observer changes during the year. It depends not only on where the observer is on the Earth, but also on what time of day and year he observes. Like when we have a winter day in South America summer night, and vice versa. There are stars visible only in summer or winter.

Third feature astronomical observations is due to the fact that all the luminaries are very far from us, so far away that neither by eye nor through a telescope can one decide which of them is closer, which is farther. They all seem equally distant to us. Therefore, the distance between objects in the sky (for example, between stars) is measured by the angle formed by the rays going to the objects from the observation point (Fig. 5). This distance is called angular and is expressed in degrees and its fractions. In this case, it is considered that two stars are not far from each other in the sky if the directions in which we see them are close (for example, stars A and I B, see Fig. 5). It is possible that the third star C, which is more distant from C in the sky, is closer to A in space than star B.

The angular distance of the star from the horizon h (see Fig. 5) is called the height of the star above the horizon.

The height of the luminaries is measured from 0° (the luminary is on the horizon) to 90° (the luminary is overhead). The position of the luminary relative to the sides of the horizon (cardinal points) is indicated using the second angle, which is called the azimuth and varies from 0 to 360 ° (counted from the south in a clockwise direction).

Measurements of the height of the luminary and its azimuth are performed with special goniometric optical instruments - theodolites.

For an approximate estimate of the angular distances in the sky, it is useful to know that the angular distance between two "dipper" stars (α and β, see Fig. 7) Ursa Major is about 5°.

The apparent dimensions of celestial objects can also be expressed in angular units. For example, the diameters of the Sun and Moon in angular measure are approximately 0.5°.

In terms of its linear size, the diameter of the Sun is larger than the diameter of the Moon by about 400 times. Why are their angular diameters o almost equal?

You will learn about how linear distances to celestial bodies and their linear dimensions are determined on the basis of angular measurements from § 12.

3. Your observations. For better assimilation astronomy, you should start observing celestial phenomena and luminaries as early as possible. Detailed instructions for observations and the use of the mobile chart of the starry sky, available in the textbook, are given in appendices VI and VII.

Historical and astronomical research, XV / Ed. ed. L.E. Maystrov- M., Science, 1980

V.A. Gurikov

HISTORY OF THE CREATION OF THE TELESCOPE

The history of the creation of the telescope is one of the most interesting questions in the history of optics. And although a lot of valuable and detailed works have been written on this topic, there are still a lot of "blank spots" in the history of the creation of the telescope. How, for example, to explain why, despite the fact that the lenses were known as early as 2500 BC. e. , and glasses were introduced at the end of the 13th century, did it take so long to arrange two lenses one after the other (after all, the first information about the practical construction of a spotting scope dates back to the end of the 16th - beginning of the 17th centuries)? In order to understand the reasons that caused such a "delay" in the appearance of the telescope, it is necessary to understand the development of optics and the laws governing the appearance of the first optical instruments.

The elements of "practical optics" - the incendiary effect of lenses and mirrors - were known in ancient times. Many indisputable testimonies of ancient authors about the incendiary effect of glasses and mirrors have survived to our time. In this way, apparently, from ancient times they received a "clean" sacrificial fire. About such ignition back in the 5th century. BC e. as a well-known phenomenon, Aristophanes mentions in the comedy "Clouds". Pliny the Elder and Seneca report the incendiary effect of glass balls. In the essay “On Temperaments”, K. Galen wrote: “And they say about Archimedes that he burned enemy triremes.” John Tsetsem describes the incendiary properties of the mirrors of Archimedes in his essay The Thousands. How Vitello imagined the burning of enemy ships by Archimedes, we see in the engraving placed on the cover of his book Perspective (Fig. 1).

For a long time, disputes arose around this historical fact. The mentioned legend has been experimentally confirmed in our days by the Greek engineer Ioannis Sakkas. In November 1973, he conducted a series of experiments in which he used a combination of mirror-polished metal shields as incendiary devices. At a signal from Saccas, the soldiers holding the shields directed the sun's rays reflected from these shields onto models of ancient Roman ships. Sakkas carried out five experiments. In the last experiment, conducted on November 6, 1973 at 12 o'clock, 70 shields were used, and the distance from the models was 55 m. Within two to three minutes, the model ships lit up.

The main optical phenomena - rectilinear propagation of light, independence of light beams, reflection from a mirror surface and refraction of light at the boundary of two transparent media - were established empirically by Euclid and Aristotle. In Heron of Alexandria, we find that “the science of vision is divided into optics, that is, the actual doctrine of vision, dioptrics, that is, the doctrine of the refraction of light, and catoptrics, that is, the doctrine of reflection.” All subsequent opticians began to call their works "Dioptric" or "Catoptric".

The opticians of antiquity, although they showed a keen interest in the nature and properties of light, did not create optical instruments as such. This was due primarily to ignorance of the structure and functions of the eye, and indeed the mechanism of vision. The possibility of obtaining real images using optical systems also remained unknown to them.

The picture of the development of optics changed dramatically in the Middle Ages, when scientists (Alhazen and others) managed to establish that vision is caused by external rays coming into the eye from objects. In this connection, Alhazen for the first time raises the question of obtaining real images from mirrors and refractive media.

However, despite the existence of a sufficient number of theoretical works on optics, practical optics, especially in terms of the use of lenses, developed extremely poorly. The relationship between science and practice in the field of optics, in fact, did not exist. This was confirmed by the invention in Italy at the end of the 13th century. points (purely empirically). “A real indisputable achievement of the 13th century,” writes S.I. Vavilov, - was the invention of glasses in Italy and their gradual distribution. On the appearance of glasses in Italy at the end of the 13th century. there are some very clear pieces of evidence. The abundance of documentary data shows that the invention took root and attracted attention. It is remarkable and at the same time sad that the 13th century opticians, who wrote a lot about refractive media, apparently did not participate in the invention of glasses.

We will try to understand what circumstances caused the appearance of glasses, which F. Engels called among the most important inventions of the 13th century.

Italian masters of the 13th century. were known throughout the world as skilled grinders and polishers. In the course of their work, they were faced with the need to bring the products of their labor close to the eye (for example, in order to control the quality of the surface treatment of the material). Therefore, their invention spectacle lenses was quite natural: they facilitated their work, made it possible to examine even the smallest details of the products they made. And at the same time, optics scientists of the XIII century. not only did not contribute to the invention of glasses, but simply did not know about their existence. Meanwhile, - notes S.I. Vavilov, - it was not a trifle, but the most remarkable result of optics for many centuries of its existence, not only in a practical sense, but also in relation to theoretical perspectives. If the true inventor of glasses became known, his name would undoubtedly occupy one of the most honorable places in the history of the science of light.

Let's figure out why it happened that spectacle lenses were discovered not by scientists, but by an artisan, by chance ?; Why did optical scientists, who by this time had a sufficient amount of knowledge, not only not participate in the invention of glasses, but also considered this invention harmful: “The main goal of vision is to know the truth, lenses for glasses make it possible to see objects larger or smaller than they are in reality; through the lenses one can see objects closer or farther, sometimes, in addition, inverted, deformed and erroneous, therefore, they do not make it possible to see reality. Therefore, if you do not want to be misled, do not use lenses. Such a recommendation was given by optics scientists in connection with ignorance of the mechanism and nature of vision. “Glasses,” he writes. S.I. Vavilov, - despite all their amazingness for a person

14th and 15th centuries and practical importance, did not become the basis further development optics. The books of Alhazen, Vitello, Bacon peacefully rested in monastic and university libraries, optical courses were read at universities as part of the quadrivium (advanced course of education. - V. G.), eminent people corrected their eyesight in old age with glasses, but optical science in the XIV and XV centuries, if not to speak about the perspective, which was important only for artists, stood still.

The first mention of a telescope is found in the English medieval scientist Roger Bacon (1214-1292). He was well acquainted with the achievements of Arabic optics and, in particular, with the work of Alhazen. Bacon was also a scientist who proclaimed completely new principles of scientific knowledge. He brilliantly foresees the future successes of experimental science. He speaks with delight about future technology: “I will tell you about the wondrous deeds of nature and art, in which there is nothing magical ... Transparent bodies can be dressed in such a way that distant objects seem close, and vice versa, so that at an incredible distance we will read the slightest letters and distinguish the smallest things, and we will also be able to see the stars as we wish.

Reading these lines, it is hard to imagine that almost 700 years ago, during the Inquisition, a brilliant monk dreamed of a telescope! His dream was a scientific fantasy. Bacon was an opponent of magic: "There is no need to resort to magical phenomena when the power of science is sufficient to produce actions," he wrote.

In the trilogy written by R. Bacon at the request of Pope Clement IV "Opus minus" ("Small Labor"), "Opus majus" ("Great Labor") and "Opus tertium" ("Third Labor") - many pages are devoted to optical topics , and there are places where we can assume that Bacon was aware of some designs of telescopes: “Thus,” he writes, “by increasing the visual angle, we will be able to read the smallest letters from great distances and count the grains of sand on the ground, so how the apparent magnitude is determined not by distance, but by the visual angle. A boy may seem like a giant, and an adult like a mountain. However, according to S.I. Vavilov, such lines, in fact, probably express only conjectures and scientific fantasies, which the addicted Doctor Mirabilis (“Wonderful Doctor” - that was the name of Bacon by his contemporaries - V. G.) did not shy away from, informing the reader along with optical theorems, for example, information about flying dragons and their caves".

The thoughts of R. Bacon were so far ahead of their time that they did not affect the course of development of contemporary science, and were subsequently consigned to oblivion.

Ideas for creating telescopic systems are found further in the manuscripts of Leonardo da Vinci. The camera and the eye are the subjects of numerous reflections and experiments of Leonardo. In his manuscripts, there are many graphic constructions of the path of rays in lenses, given experimental method aberration definitions. Leonardo is the indisputable pioneer of photometry as an exact measuring science. Peru Leonardo owns drawings of machines for polishing concave mirrors, he examines in detail technological process production of spectacle lenses. Leonardo was the first to make an attempt to transfer natural science knowledge to the applied field.

Of all the variety of Leonardo's works in the field of optics, we will be interested in only one question: was Leonardo's telescope (telescopic device) implemented? “Undoubtedly,” writes S.I. Vavilov, - that Leonardo not only dreamed of telescopic devices, but actually implemented them. ”We will try to restore the actual course of events.

Thus ends the first pages of the history of the telescope. After them there will be many more bright pages (the creation of a mirror telescope, the invention of achromatic optics, etc.).

The emergence and development of telescopic systems in the XVII century. caused a real revolution in both optics and astronomy. Actually, it was thanks to the wide practical use of telescopic systems that technical optics as a science was born, and new instruments (telescopes, helioscopes, etc.) appeared in astronomy, making it possible, on the one hand, to study the Universe more deeply, and on the other hand, contributing to further progress in development of technical optics.

LITERATURE

1. Riekher Rolf. Fernrohre und ihre Meister. - Berlin, 1957.

2. King H. C. The History of the Telescope. - London, 1955.

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4. Kisa A. Das Glas im Altertum: 3 Bd. - Leipzig, 1908.

5. Feldhaus F. M. Die ältesten optischen Hilfsmittel. - In: Der Sternfreund, 1936, Nr. one.

6 Galeni Claudii Opera omnia: t. 1 / Ed. CG. Kuhn. - Lipsiae, 1821.

7. Tetes Joahnis. Chiliades / Ed. th. Kiesling. - Hildesheim, 1963.

8. Ευάγγελου Σ. Σταμάτη. Αρχιμηδους άπαντα. - Αθ·ηναΐ, 1974. 9. Vavilov S.I. Sobr. cit.: vol. III. - M.: Publishing House of the Academy of Sciences of the USSR, 1956.

10. Opticae Thesaurus libri Septem, nu primum editi, a Federico Risnero Basileae per Episcopios, 1572.

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A telescope is a unique optical instrument designed to observe celestial bodies. The use of instruments allows us to consider a variety of objects, not only those that are located near us, but also those that are thousands of light years away from our planet. So what is a telescope and who invented it?

First inventor

Telescopic devices appeared in the seventeenth century. However, to this day there is a debate about who invented the telescope first - Galileo or Lippershey. These disputes are related to the fact that both scientists at about the same time were developing optical devices.

In 1608, Lippershey developed eyeglasses for the nobility, allowing them to see distant objects up close. At this time, military negotiations were underway. The army quickly appreciated the benefits of the development and suggested that Lippershey not assign copyright to the device, but modify it so that it could be viewed with two eyes. The scientist agreed.

The new development of the scientist could not be kept secret: information about it was published in local print media. Journalists of that time called the device a spotting scope. It used two lenses, which made it possible to enlarge objects and objects. From 1609, pipes with a threefold increase were sold with might and main in Paris. Since this year, any information about Lippershey disappears from history, and information about another scientist and his new discoveries appears.

Around the same time, the Italian Galileo was engaged in grinding lenses. In 1609, he presented to society a new development - a telescope with a threefold increase. Galileo's telescope had a higher image quality than Lippershey's tubes. It was the brainchild of the Italian scientist who received the name "telescope".

In the seventeenth century, telescopes were made by Dutch scientists, but they had poor image quality. And only Galileo managed to develop such a technique for grinding lenses, which made it possible to clearly enlarge objects. He was able to get a twenty-fold increase, which was a real breakthrough in science in those days. Based on this, it is impossible to say who invented the telescope: if, according to the official version, it was Galileo who introduced the world to a device that he called a telescope, and if you look at the version of the development of an optical device for magnifying objects, then Lippershey was the first.

First observations of the sky

After the advent of the first telescope, unique discoveries were made. Galileo applied his development to tracking celestial bodies. He was the first to see and sketch lunar craters, spots on the Sun, and also considered the stars of the Milky Way, satellites of Jupiter. Galileo's telescope made it possible to see the rings of Saturn. For your information, there is still a telescope in the world that works on the same principle as Galileo's device. It is located at the York Observatory. The device has a diameter of 102 centimeters and regularly serves scientists to track celestial bodies.

Modern telescopes

Over the centuries, scientists have constantly changed the devices of telescopes, developed new models, and improved the magnification factor. As a result, it was possible to create small and large telescopes with different purposes.

Small ones are usually used for home observations of space objects, as well as for observing nearby space bodies. Large devices allow you to view and take pictures of celestial bodies located thousands of light years from Earth.

Types of telescopes

There are several types of telescopes:

Mirrored.
Lens.
catadioptric.

Galilean refractors are classified as lens refractors. Reflective type devices are referred to as mirror devices. What is a catadioptric telescope? This is a unique modern development that combines a lens and a mirror device.

Lens telescopes

Telescopes play an important role in astronomy: they allow you to see comets, planets, stars and other space objects. One of the first developments were lens devices.

Every telescope has a lens. This is the main part of any device. It refracts rays of light and gathers them at a point called a focus. It is in it that the image of the object is built. An eyepiece is used to view the image.

The lens is placed so that the eyepiece and focus match. In modern models, movable eyepieces are used for convenient observation through a telescope. They help to adjust the sharpness of the image.

All telescopes have aberration - a distortion of the object in question. Lens telescopes have several distortions: chromatic (red and blue rays are distorted) and spherical aberration.

Mirror models

Mirror telescopes are called reflectors. A spherical mirror is mounted on them, which collects the light beam and reflects it with the help of a mirror onto the eyepiece. Chromatic aberration is not characteristic of mirror models, since light is not refracted. However, mirror instruments exhibit spherical aberration, which limits the field of view of the telescope.

Graphic telescopes use complex structures, mirrors with complex surfaces that differ from spherical ones.

Despite the complexity of the design, mirror models are easier to develop than lens counterparts. Therefore, this type is more common. The largest diameter of a mirror-type telescope is more than seventeen meters. On the territory of Russia, the largest device has a diameter of six meters. For many years it was considered the largest in the world.

Telescope Specifications

Many people buy optical devices for observing space bodies. When choosing a device, it is important to know not only what a telescope is, but also what characteristics it has.

Increase. The focal length of the eyepiece and the object is the magnification of the telescope. If the focal length of the lens is two meters, and the eyepiece is five centimeters, then such a device will have a magnification of forty times. If the eyepiece is replaced, the magnification will be different.
Permission. As you know, light is characterized by refraction and diffraction. Ideally, any image of a star looks like a disk with several concentric rings, called diffraction rings. The dimensions of the disks are limited only by the capabilities of the telescope.

Telescopes without eyes

And what is a telescope without an eye, what is it used for? As you know, each person's eyes perceive the image differently. One eye can see more and the other less. So that scientists can see everything they need to see, they use telescopes without eyes. These devices transmit the image to the monitor screens, through which everyone sees the image exactly as it is, without distortion. For small telescopes, for this purpose, cameras have been developed that are connected to devices and take pictures of the sky.

The most modern methods of space vision is the use of CCD cameras. These are special light-sensitive microcircuits that collect information from the telescope and transfer it to a computer. The data received from them is so clear that it is impossible to imagine what other devices could receive such information. After all, the human eye cannot distinguish all shades with such high clarity, as modern cameras do.

To measure the distances between stars and other objects, use special devices- spectrographs. They are connected to telescopes.

A modern astronomical telescope is not one device, but several at once. The received data from several devices are processed and displayed on monitors in the form of images. Moreover, after processing, scientists receive images of very high definition. It is impossible to see the same clear images of space with the eyes through a telescope.

radio telescopes

Astronomers use huge radio telescopes for their scientific developments. Most often they look like huge metal bowls with a parabolic shape. Antennas collect the received signal and process the received information into images. Radio telescopes can only receive one wave of signals.

infrared models

A striking example of an infrared telescope is the Hubble apparatus, although it can be optical at the same time. In many ways, the design of infrared telescopes is similar to the design of optical mirror models. Heat rays are reflected by a conventional telescopic lens and focused at one point, where the device that measures heat is located. The resulting heat rays are passed through thermal filters. Only then does the photo take place.

Ultraviolet telescopes

Film may be exposed to ultraviolet light when photographed. In some part of the ultraviolet range, it is possible to receive images without processing and exposure. And in some cases it is necessary that the rays of light pass through a special design - a filter. Their use helps to highlight the radiation of certain areas.

There are other types of telescopes, each of which has its own purpose and special characteristics. These are models such as X-ray and gamma-ray telescopes. According to their purpose, all existing models can be divided into amateur and professional. And this is not the whole classification of devices for tracking celestial bodies.