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What is a telescope? The James Webb Telescope is the most powerful telescope in the world (28 photos)

A telescope is a device designed to observe celestial objects - planets, stars, nebulae and galaxies. The word “telescope” is derived from two Greek words meaning “afar” and “looking.”

The first device for observing distant objects - a spotting scope - was invented at the beginning of the 17th century. Danish optician I. Lippershey. Its diagram was as follows: a biconvex lens was fixed at the front end of the pipe - an objective. Passing through the lens, the light is collected at a focal point, where an image of the celestial body is obtained. At the other end of the tube there is an eyepiece that allows you to view the image enlarged. The magnification power of this optical instrument depends on the size and convexity of the lens and eyepiece.

Soon after the invention of the pipe, the Italian scientist Galileo Galilei learned about it. He became interested in the task of constructing a “perspective,” as the telescope was then called. At first he built a pipe with threefold magnification, and later increased this figure to thirtyfold.

Galileo was the first to use a telescope for astronomical observations. He first did this on January 7, 1610. Even the modest capabilities of Galileo's trumpet were enough for several discoveries.

Galileo discovered that the surface of the Moon is uneven and, like on Earth, there are mountains and valleys. The mystery of the Milky Way has been revealed. The Italian discovered that the Galaxy is nothing more than a collection of a huge number of stars.

In addition, Galileo immediately discovered four satellites of Jupiter, which he named “Medicean stars” in honor of the Grand Duke of Tuscany Cosimo II de’ Medici.

In the book “Star Messenger” the scientist spoke about his observations. His discoveries sparked intense controversy. Many considered Galileo's discoveries to be an illusion caused by a telescope.

Galileo continued his observations. Looking at Saturn through a telescope, he discovered spots on both sides of the planet. He decided that these were the same satellites as those of Jupiter. Two years later, to his bewilderment, the researcher saw the same planet “completely alone.” He was never able to find an explanation for the riddle. Only half a century later, the Dutchman H. Huygens discovered that in fact it was a ring surrounding Saturn.

Further studies of the starry sky allowed Galileo to make several more discoveries. He noticed that Venus, “imitating” the Moon, changes its appearance. This served as decisive proof that Venus, in accordance with Copernicus' theory, revolves around the Sun.

Galileo discovered spots on the Sun and became convinced that the Sun rotates on its axis.

Independently of Galileo, and even before him, in 1609, the outer face of the Moon was sketched by the English mathematician T. Harriot using a telescope. And the priority of discovering the satellites of Jupiter was challenged by the Italian by the German S. Marius.

Galileo was tried by the Inquisition for promoting the ideas of Copernicus and publicly renounced his views. The Church rehabilitated him only in 1980. In the same year, his observation logs were re-examined by historians of astronomy. They established that in the winter of 1612–1613. The scientist observed the planet Neptune, although he mistook it for a star.

The baton of creating telescopes was picked up from Galileo by the Polish astronomer and observer Jan Hevelius. In 1641, in Gdansk, he equipped an observatory on the roofs of three of his houses. Hevelius began creating his own telescopes with relatively small pipes 2–4 m long. By improving manufacturing techniques, he managed to increase the size of telescopes to 10–20 m. The largest of Hevelius’ telescopes did not fit in his observatory, and this instrument had to be installed outside the city, mounted on a special mast 30 m high. The length of the tube of this telescope reached 45 m.

Hevelius, like Galileo, used a biconvex lens as a lens for his pipes. Such lens telescopes are called refractor telescopes. By bringing his telescopes to very large sizes, Hevelius was able to achieve fairly significant magnifications with satisfactory image quality. But he was unable to expand the capabilities of his telescopes to observe faint objects. This is because detecting faint objects requires increasing the lens surface. But the creation of large lens telescopes was fraught with insurmountable technical difficulties.

Astronomers were able to solve this problem by using concave mirrors as lenses. Making large concave mirrors is much easier than making lenses of the same size. Telescopes with mirror lenses are called reflecting telescopes, or reflecting telescopes.

In a reflector, a concave mirror is placed at the lower end of the tube. Reflecting from it, the light is collected at the upper end of the tube, where it is directed to the observer using a small mirror.

I. Newton made small telescopes and reflectors in his home laboratory in the 60–70s of the 17th century. He made the first large telescopes of this type at the end of the 18th century. Englishman V. Herschel. They had huge lenses that made it possible to observe very faint objects. The largest of Herschel's mirror telescopes had a mirror with a diameter of 120 cm and a tube length of 12 m. It moved up and down using blocks, and rotated around its axis on a special platform. In 1789, using his telescope, Herschel discovered the first planet in the solar system, named Uranus.

Reflector telescopes also have serious disadvantages. The field of view of such telescopes is usually small: even the disk of the Moon does not fit into it. This causes serious inconvenience, especially when photographing large objects, since viewing requires moving the entire instrument. In addition, reflecting telescopes are in most cases not suitable for precise positional measurements.

In this regard, at the beginning of the 19th century. Design thought again turned to lens telescopes and refractors. Their rapid improvement was due to the skill of J. Fraunhofer. He combined lenses from two different types of glass in the lens - crown glass and flint glass. Both are made from quartz glass, differing only in the additives used. The different refractive indices of light in these glasses make it possible to sharply reduce the coloration of images - the main drawback of lens systems, which Jan Hevelius unsuccessfully fought against.

Fraunhofer was the first to learn how to make large lens lenses, whose diameters were several tens of centimeters. He managed to overcome the difficulties associated with the intricacies of glass melting technology and cooling the finished glass disk. The disk from which the lens is to be ground must be welded without bubbles and cooled in such a way that no stress arises in it. Stresses can cause uneven changes in the shape of a lens that is ground to within ten-thousandths of a millimeter.

Fraunhofer not only improved the optics of the refractor telescope, but also turned it into a high-precision measuring instrument. His predecessors failed to find a good solution on how to guide the telescope behind the star. Due to the daily movement of the celestial sphere, the star is constantly moving and, moving along a curve, quickly leaves the field of view of a stationary telescope.

Fraunhofer tilted the telescope's rotation axis, pointing it toward the celestial pole. To track the star, it was enough to rotate it around the polar axis alone. Fraunhofer automated this process by adding a clock mechanism to the telescope.

Fraunhofer balanced all the moving parts of the telescope. Despite their heavy weight, they obey light pressure.

In 1824, Fraunhofer manufactured a first-class telescope for the observatory in Dorpat.

In the second half of the 19th century. The best telescopes were made by American optics. Clark. In 1885, he made the largest lens at that time with a diameter of 76 cm for the Pulkovo refractor telescope. In 1888, a telescope with a lens diameter of 92 cm made by Clark was built on Mount Hamilton near San Francisco. Soon, a telescope with a 102 cm lens, which Clark also made, was installed on the roof of the University of Chicago Observatory.

By design, all of the above telescopes were a repetition of Fraunhofer telescopes. They were easy to control, but due to the absorption of light in the lens glass and bending of the pipes, the dimensions of these telescopes turned out to be limiting for structures of this kind.

The attention of astronomers and designers again turned to telescopes and reflectors.

In 1919, a reflecting telescope with a mirror diameter of 2.5 m came into operation in Mount Wilson, California. The experience of its manufacture was taken into account in the project of a 5-meter telescope, the construction of which took a quarter of a century. It went into operation in 1949 at the Mount Palomar Observatory.

After the Great Patriotic War, the largest reflecting telescope in Europe with a mirror diameter of 2.6 m was put into operation at the Crimean Astrophysical Observatory of the USSR Academy of Sciences. The accumulated experience allowed Soviet opticians to build the world's largest reflecting telescope with a mirror diameter of 6 m. There are 24 of them The one-meter tube weighs 300 tons, and the mirror - 42 tons. The telescope mirror in any position must be in a state of weightlessness. It rests on 60 supporting points. Three of them are load-bearing, the rest are supporting.

The instrument is guided behind the stars by a computer. It calculates the displacement of the stars, making corrections for the effects of refraction and the bending of the tube, and rotates the telescope at the required speed. The mass of the moving part of the telescope is 650 tons.

Unlike the paragalactic mount used by Fraunhofer, this telescope uses an azimuthal mount. The telescope itself is called BTA - large azimuthal telescope.

After a long search for a location, the BTA telescope was installed in the foothills of the North Caucasus near the village of Zelenchukskaya at an altitude of 2070 m and went into operation in 1975.

In 1931, the American K. Jansky, using an antenna designed to study thunderstorm radio interference, registered radio emission of cosmic origin (from the Milky Way). Its wavelength was 14.6 m.

In 1937, in the USA, G. Reber built the first radio telescope for studying cosmic radio emission - a reflector with a diameter of 9.5 m.

The most important characteristic of optical instruments is resolution. It is equal to the smallest angle at which two objects are distinguished by this device as independent. For the human eye, under normal conditions, the resolution is about G. The resolution of a telescope increases with increasing diameter of the telescope and decreasing the wavelength of the received radiation. For optical telescopes, this figure is limited by the atmosphere and does not exceed 0.3 m.

In radio astronomy, this figure was much lower for many years, since the length of radio waves is tens of thousands of times longer than the wavelength of visible light. In this regard, the need arose to build radio telescopes with huge lenses - paraboloids. But the resolution of radio telescopes remained insufficient for a long time. It was minutes and tens of minutes. This did not make it possible to study the fine structure of objects observed in the sky and even determine their extent.

This difficulty was overcome by the construction of radio interferometers. They are two radio telescopes separated from each other by hundreds and thousands of kilometers. Comparison of simultaneous observations on both telescopes makes it possible to achieve a resolution of up to 0.00G. The first radio interferometer was built in Australia in 1948. In 1967, the first observations were made using interferometers with independent signal recording and ultra-large bases.

In 1953, the first cruciform radio telescope was built. A fully rotating radio telescope with a paraboloid diameter of 76 m was built at the English Jodrell Bank Observatory. Later in Effelsberg (Germany), at the Radio Engineering Institute. M. Planck built a telescope with a mirror diameter of 100 m.

The largest fixed radio telescope with a fixed spherical bowl with a diameter of 300 m was built in a specially prepared crater of the Arecibo volcano (Puerto Rico).

What a telescope is is known to many, but it is usually quite vague. Even fewer people saw it, and even fewer who had the opportunity to use this tool. Although today, if desired, a fairly good telescope can be purchased in a store. But, before you go shopping, you need to at least have an idea of what it is and why it is needed, so that the box does not gather dust somewhere on the balcony.

So, a telescope is “an instrument that collects electromagnetic radiation from a distant object and directs it to a focus where a magnified image of the object is formed or an amplified signal is generated.” That's how they wrapped it up! The most common and well-known are optical telescopes - they magnify distant objects and allow you to examine or photograph their small details, because visible light is also a type of electromagnetic radiation. But there are telescopes that operate in other ranges, for example, in the X-ray and radio ranges, which is why the concept of a telescope is so broad.

Radio telescopes are similar to huge satellite “dishes”, and in fact the principle of their operation is the same. They collect radio emissions, which are then amplified and studied. These are the “ears” of astronomers with which they listen to the sky. And they hear quite a lot...

And yet, we associate the concept of a telescope with an optical system - a sort of telescope on a stand. Of course, there are some, but this is a small proportion of the total number of modern systems.

The first telescope, consisting of a pair of lenses, is believed to have been invented by Galileo Galilei in 1609, but this is not true. A year earlier, in 1608, the Dutchman Hans Lipperschlei attempted to patent a device made from a tube with inserted lenses, which he called a spyglass, but was rejected due to the simplicity of the design. And even earlier, in 1450, Thomas Digges tried to look at the stars using a lens and a concave mirror, but he never brought the idea to completion. Galileo was “in the right place at the right time,” and he was the first to point a simple telescope at the sky, discovered mountains on the Moon and many other interesting things... Therefore, he can be called the first astronomer to use a telescope.

Galileo's telescope gave rise to the era of refractor telescopes. This is the name given to a system of lenses that produces an image due to the refraction of light in the lenses. The lens into which the light enters is called the objective lens. The larger it is, the more light it collects and the telescope can show more faintly luminous objects. The longer the focal length of the lens, the greater the magnification the telescope provides. Therefore, telescopes with huge tubes - 3 meters or more in length - were widespread. The lens through which the observer looks is called the eyepiece. On the contrary, it should have a small focal length. By the way, the magnification of a telescope can be obtained by dividing the focal length of the lens by the focal length of the eyepiece.

The first telescopes produced poor images. Over time, the system became more complicated - both the lens and the eyepiece consist of several lenses made of different types of glass, which compensate for each other’s shortcomings, and a modern refracting telescope is a pretty good and powerful instrument.

In 1720, Isaac Newton created the first reflecting telescope. It had a metal concave mirror with a diameter of only 40 millimeters, but it gave an excellent picture. Reflected light does not have the same imperfections and distortions as refracted light, which is why mirror telescopes of the Newtonian system have become extremely widespread. They had a fairly compact size compared to lens refractors with a fairly powerful large mirror - the lens. And now Newtonian telescopes are the most popular instrument of amateur astronomers. Many people make them themselves, and now there are many quite strong and inexpensive models on sale.

Over time, telescopes - refractors and reflectors - have produced many modifications that have their own advantages and disadvantages. Refractors traditionally have high magnification and are used to study bright but distant objects - planets, the Moon, the Sun, nebulae and stars. Reflectors have a large lens - the mirror collects much more light due to its larger diameter, so they have a higher aperture ratio. They are better suited for observing faint objects - nebulae, galaxies, faint stars. Of course, you can use any model for any purpose, but when choosing, you need to take into account the future conditions of use. If you want to look more at planets, the Moon or comets, you can buy both a refractor and a reflector, and if you are more interested in observing and photographing nebulae, variable stars or galaxies, it is better to choose a mirror reflector.

All optical ones can be divided according to the type of the main light-collecting element into lens, mirror and combined - mirror-lens. All systems have their own advantages and disadvantages, and when choosing a suitable system, several factors must be taken into account - observation goals, conditions, requirements for transportability and weight, level of aberrations, price, etc. Let's try to give the main characteristics of the most popular types of telescopes today.

Refractors (lens telescopes)

Historically, they were the first to appear. The light in such a telescope is collected using a biconvex lens, which is the objective of the telescope. Its action is based on the property of convex lenses to refract light rays and collect them at a certain point - the focus. Therefore, lens telescopes are often called refractors(from lat. refract - refract).

IN Galileo's refractor(created in 1609) two lenses were used to collect as much starlight as possible to allow the human eye to see it. The first lens (objective) is convex, it collects light and focuses it at a certain distance, and the second lens (playing the role of an eyepiece) is concave, turning the converging beam of light rays back into parallel. Galileo's system produces an upright, uninverted image, but suffers greatly from chromatic aberration, which spoils the image. Chromatic aberration appears as false coloration of the edges and details of an object.

Was more perfect Kepler refractor(1611), in which a convex lens acted as an eyepiece, the front focus of which was combined with the rear focus of the objective lens. In this case, the image turns out to be inverted, but this is unimportant for astronomical observations, but a measuring grid can be placed at the focal point inside the tube. The scheme proposed by Kepler had a strong influence on the development of refractors. True, it was also not free from chromatic aberration, but its influence could be reduced by increasing the focal length of the lens. Therefore, refractors of that time, with modest lens diameters, often had a focal length of several meters and a corresponding length of the tube or did without it at all (the observer held the eyepiece in his hands and “caught” the image that was created by the lens mounted on a special tripod).

These difficulties of refractors in their time even led the great Newton to the conclusion that it was impossible to correct the chromaticism of refractors. But in the first half of the 18th century. appeared achromatic refractor.

Among amateur instruments, the most common are two-lens achromat refractors, but more complex lens systems also exist. Typically, an achromatic refractor lens consists of two lenses made of different types of glass, one collecting and the other diverging, and this can significantly reduce spherical and chromatic aberrations (image distortions inherent in a single lens). At the same time, the telescope tube remains relatively small.

Further improvement of refractors led to the creation apochromats. In them, the influence of chromatic aberration on the image is reduced to an almost imperceptible value. True, this is achieved through the use of special types of glass, which are expensive to produce and process, therefore the price of such refractors is several times higher than for achromats of the same aperture.

Like any other optical system, refractors have their pros and cons.

Advantages of refractors:

comparative simplicity of design, providing ease of use and reliability;

practically no special maintenance required;

fast thermal stabilization;

excellent for observing the Moon, planets, double stars, especially with large apertures;

the absence of central shielding from the secondary or diagonal mirror provides maximum image contrast;

good color rendering in achromatic version and excellent in apochromatic version;

the closed tube eliminates air flows that spoil the image and protects the optics from dust and dirt;

The lens is manufactured and adjusted by the manufacturer as a single unit and does not require adjustments by the user.

Disadvantages of refractors:

the highest cost per unit of lens diameter in comparison with reflectors or catadioptrics;

as a rule, greater weight and dimensions compared to reflectors or catadioptrics of the same aperture;

price and bulkiness limit the largest practical aperture diameter;

generally less suitable for observing small and faint deep-sky objects due to practical aperture limitations.

Bresser Mars Explorer 70/700 is a classic small achromat. The high-quality optics of this model allow you to obtain a bright and clear image of the object, and the included eyepieces allow you to set magnification up to 260x. This telescope model is successfully used to photograph the surface of the Moon and the disks of the planets.

4-lens achromat refractor (Pezval). Compared to an achromat, it has less chromatism and a larger useful field of view. Auto guidance system. Suitable for astrophotography. The combination of a short throw and a large aperture makes the auto-aiming Bresser Messier AR-152S one of the most attractive models for observing large celestial objects. Nebulas and distant galaxies will appear before you in all their glory, and using additional filters, you will be able to study them in detail. We recommend using this telescope for lunar and planetary observations, studying deep space objects, and astrophotography.

For anyone who wants to learn the basics of astronomy and observing stars and planets, we recommend the Levenhuk Astro A101 60x700 refracting telescope. Also, this telescope will satisfy the higher demands of an experienced observer, since this model provides very high image quality.

For many people passionate about astronomy, it is extremely important to use every free minute for interesting research. However, unfortunately, you don’t always have a telescope at hand - many of them are so heavy and bulky that it is not possible to carry them with you all the time. With a refracting telescope
Levenhuk Skyline 80x400 AZ Your ideas about astronomical observations will change: now you can carry a telescope with you in the car, on a plane, on a train, that is, wherever you go, you will be able to devote time to your hobby.

The Orion GoScope 70 refracting telescope is a portable achromat that will allow you to study distant celestial bodies with high clarity. In fact, this telescope is already fully assembled and ready for use, and placed in a special convenient backpack. All you need to do is extend the aluminum tripod and place the telescope on it.

Reflectors (mirror telescopes)

Or reflector(from lat. reflectio - reflect) is a telescope whose lens consists only of mirrors. Just like a convex lens, a concave mirror is capable of collecting light at a certain point. If you place an eyepiece at this point, you will be able to see the image.

One of the first reflectors was the reflecting telescope Gregory(1663), who invented a telescope with a parabolic primary mirror. The image that can be observed through such a telescope is free from both spherical and chromatic aberrations. The light collected by the large main mirror is reflected from a small elliptical mirror mounted in front of the main mirror and is brought out to the observer through an opening in the center of the main mirror.

Disillusioned with contemporary refractors, I. Newton in 1667 he began developing a reflecting telescope. Newton used a metal primary mirror (glass mirrors coated with silver or aluminum came later) to collect the light, and a small flat mirror to deflect the collected light at right angles and out the side of the tube into the eyepiece. Thus, it was possible to cope with chromatic aberration - instead of lenses, this telescope uses mirrors that equally reflect light of different wavelengths. The main mirror of a Newtonian reflector can be parabolic or even spherical if its relative aperture is relatively small. A spherical mirror is much easier to make, so a Newtonian reflector with a spherical mirror is one of the most affordable types of telescopes, including for self-production.

Scheme proposed in 1672 by Laurens Cassegrain, externally resembles the Gregory reflector, but has a number of significant differences - a hyperbolic convex secondary mirror and, as a result, a more compact size and smaller central shielding. The traditional Cassegrain reflector is low-tech in mass production (complex mirror surfaces - parabola, hyperbola), and also has an undercorrected coma aberration, however, its modifications remain popular in our time. In particular, in a telescope Ritchie-Chretien hyperbolic primary and secondary mirrors are used, which gives it the opportunity to develop large fields of view, free from distortion, and, which is especially valuable, for astrophotography (the famous Hubble Orbital Telescope was designed according to this scheme). In addition, based on the Cassegrain reflector, popular and technologically advanced catadioptric systems were later developed - Schmidt-Cassegrain and Maksutov-Cassegrain.

Nowadays, a telescope made according to Newton’s scheme is most often called a reflector.. Having low spherical aberration and a complete absence of chromatism, it is, however, not completely free from aberrations. Already not far from the axis, coma (non-isoplanatism) begins to appear - an aberration associated with the unequal magnification of different annular zones of the aperture. Coma leads to the fact that the image of the star does not look like a circle, but like a projection of a cone - the sharp and bright part towards the center of the field of view, the dull and rounded part away from the center. Coma is directly proportional to the distance from the center of the field of view and the square of the lens diameter, so it is especially pronounced in the so-called “fast” (high-aperture) Newtons at the edge of the field of view. To correct coma, special lens correctors are used, installed in front of the eyepiece or camera.

As the most affordable reflector to make yourself, the Newton is often made on a simple, compact and practical Dobsonian mount and in this form is the most portable telescope given the available aperture. Moreover, the production of “Dobsons” is carried out not only by amateurs, but also by commercial manufacturers, and telescopes can have apertures of up to half a meter or more.

Advantages of reflectors:

lowest cost per unit of aperture diameter compared to refractors and catadioptrics - large mirrors are easier to produce than large lenses;

relatively compact and transportable (especially in the Dobsonian version);

due to the relatively large aperture, they work excellently for observing dim objects in deep space - galaxies, nebulae, star clusters;

produce bright images with low distortion and no chromatic aberration.

Disadvantages of reflectors:

central shielding and extensions of the secondary mirror reduce the contrast of image details;

a massive glass mirror requires time for thermal stabilization;

the open pipe is not protected from dust and thermal air currents that spoil the image;

periodic adjustment of the mirror positions (adjustment or collimation) is required, which tends to be lost during transportation and operation.

Do you want to start astronomical observations for the first time? Or maybe you already have extensive experience in such research? In both cases, your reliable assistant will be the Newtonian reflector Bresser Venus 76/700 - a telescope, thanks to which you will always easily and effortlessly obtain images of high quality and clarity. You will examine in detail not only the surface of the Moon, including many craters, you will see not only the large planets of the Solar System, but also some distant nebulae, such as the Orion Nebula.

The Bresser Pollux 150/1400 EQ2 telescope is created according to Newton's scheme. This allows, while maintaining high optical characteristics (focal length reaches 1400 mm), to significantly reduce the overall dimensions of the telescope. Thanks to its 150 mm aperture, the telescope is able to collect a large amount of light, which makes it possible to observe fairly faint objects. With Bresser Pollux you can observe the planets of the solar system, nebulae and stars up to 12.5 stars. Vel., including double. The maximum useful magnification is 300x.

If you are attracted by the unknown nature of objects located in the depths of outer space, then you, without a doubt, need a telescope that can bring these mysterious objects closer and allow you to study them in detail. We are talking about Levenhuk Skyline 130x900 EQ – a Newtonian reflecting telescope designed specifically for deep space exploration.

The Levenhuk SkyMatic 135 GTA reflector is an excellent telescope for amateur astronomers who require an automatic pointing system. The azimuth mount, auto-guidance system and large aperture of the telescope allow you to observe the Moon, planets, as well as most large objects from the NGC and Messier catalogs.

The SpaceProbe 130ST EQ telescope can be called a short-focus version of the SpaceProbe 130 model. This is also a reliable and high-quality reflector mounted on an equatorial mount. The difference is that the 130ST EQ's higher aperture makes deep space objects more accessible. The telescope also has a shorter tube - only 61cm, while the 130 EQ model has an 83cm tube.

Catadioptric (mirror lens) telescopes

(or catadioptric) telescopes use both lenses and mirrors to construct an image and correct aberrations. Among catadioptrics, the most popular among astronomy enthusiasts are two types of telescopes based on the Cassegrain scheme - Schmidt-Cassegrain and Maksutov-Cassegrain.

In telescopes Schmidt-Cassegrain (S-C) The main and secondary mirrors are spherical. Spherical aberration is corrected by a full-aperture Schmidt correction plate placed at the entrance to the pipe. This plate appears flat from the outside, but has a complex surface, the manufacture of which is the main difficulty in manufacturing the system. However, the American companies Meade and Celestron have successfully mastered the production of the Sh-K system. Among the residual aberrations of this system, the most noticeable are field curvature and coma, the correction of which requires the use of lens correctors, especially when photographing. The main advantage is a short tube and less weight than a Newtonian reflector of the same aperture and focal length. In this case, there are no stretch marks for attaching the secondary mirror, and the closed pipe prevents the formation of air flows and protects the optics from dust.

System Maksutov-Cassegrain(M-K) was developed by the Soviet optician D. Maksutov and, like Sh-K, has spherical mirrors, and aberrations are corrected by a full-aperture lens corrector - a meniscus (convex-concave lens). Therefore, such telescopes are also called meniscus reflectors. A closed pipe and the absence of stretch marks are also advantages of M-K. By selecting system parameters, almost all aberrations can be corrected. The exception is the so-called spherical aberration of higher orders, but its influence is small. Therefore, this scheme is very popular and is produced by many manufacturers. The secondary mirror can be implemented as a separate unit, mechanically fixed to the meniscus, or as an aluminized central section of the back surface of the meniscus. In the first case, better correction of aberrations is ensured, in the second - lower cost and weight, greater manufacturability in mass production and elimination of the possibility of misalignment of the secondary mirror.

In general, with the same manufacturing quality, the M-K system is capable of producing a slightly higher quality image than the Sh-K with similar parameters. But large M-K telescopes require more time for thermal stabilization, because a thick meniscus cools down much longer than the Schmidt plate, and for M-K the requirements for the rigidity of the corrector mount increase, and the entire telescope becomes heavier. Therefore, the use of the M-K system for small and medium apertures, and the Sh-K system for medium and large apertures can be traced.

There are also Schmidt-Newton catadioptric systems And Maksutov-Newton, having the characteristic features of the designs mentioned in the title and better correction of aberrations. But at the same time, the dimensions of the pipe remain “Newtonian” (relatively large), and the weight increases, especially in the case of a meniscus corrector. In addition, catadioptric systems include systems with lens correctors installed in front of the secondary mirror (Klevtsov system, “spherical cassegrains”, etc.).

Advantages of catadioptric telescopes:

high level of aberration correction;

versatility - well suited for observing planets and the Moon, and for deep space objects;

where there is a closed pipe, it minimizes thermal air flows and protects from dust;

greatest compactness with equal aperture in comparison with refractors and reflectors;

Large apertures cost significantly less than comparable refractors.

Disadvantages of catadioptric telescopes:

the need for relatively long thermal stabilization, especially for systems with a meniscus corrector;

higher cost than reflectors of equal aperture;

complexity of the design, making it difficult to independently adjust the instrument.

Levenhuk SkyMatic 105 GT MAK is an excellent auto-aiming telescope that is small in size and weight, but at the same time has high resolution and produces high-quality images. The compactness of the design is achieved through the use of the Maksutov-Cassegrain scheme. The Levenhuk SkyMatic 105 GT MAK telescope is powerful enough to observe details on the disks of the Moon and planets, and is also capable of showing compact globular clusters and planetary nebulae.

Every astronomer, whether a beginner or a more experienced amateur, knows the excitement that covers him when observing, how he wants to completely immerse himself in the fabulous surreal world of stars, planets, comets, asteroids and other celestial bodies, as mysterious as they are beautiful. But sometimes the pleasure of observing can be seriously spoiled, in particular, if the telescope is heavy and bulky. In this case, the lion's share of time is spent on carrying, assembly and setup. The Maksutov-Cassegrain Orion StarMax 102mm EQ Compact Mak is one of the most compact telescopes with a 102mm lens, and it won't let you waste your precious observing time on anything else.

The Vixen VMC110L telescope on a Sphinx SXD mount is a good choice for astrophotography. The telescope's optics combine the compactness of the Cassegrain system with a large focal length. To correct aberrations, a lens corrector is used, located in front of the secondary mirror. In addition, it is worth noting the reliable and rigid Sphinx SXD computer-guided mount. In addition to a real computer planetarium in the control panel with a large color screen, it has a periodic error correction function, a polar finder - the main thing that is necessary for the most accurate pointing of the telescope to the photographic object.

Who invented the telescope?

It is believed that the scientist Galileo Galilei was the first to use lenses to bring distant objects closer. In 1610, he constructed a telescope, through which he saw craters on the Moon, satellites of Jupiter and other interesting details located at a distance in space. But at the same time, during the excavations of Troy, archaeologists found crystal lenses, and this means that it is possible that people had the ability to bring objects closer before.

Telescopes are usually installed in special structures designed for observing various natural phenomena. Observatories with a rotating dome and located mainly on hills are equipped with entire complexes of telescopes.

Telescopes and innovation

The further the development of astronomy and other sciences went, the more advanced telescopes became. It has become possible to study objects in the electromagnetic spectrum using complex systems of detectors and sensors. Such equipment operates in different wavelength ranges.

Today there are telescopes operating in the X-ray range and radio range. All these telescopes are radically different from each other, but at the same time they have one common function: they give a person the opportunity to study in detail objects located at very distant distances.

Modern telescopes (more precisely, radio telescopes) are powerful equipment that analyzes and accumulates electromagnetic radiation from a distant object and directs it into focus. And already there an enlarged image of the object is formed or an amplified signal is generated, allowing a detailed examination of the object being studied. Space can also be explored using space thermal imagers, which transmit images of the surfaces of distant objects in the infrared range.

Probably the most famous telescope on the planet is the Hubble Space Telescope. This innovative equipment is located in Earth orbit and is more like a space observatory. The telescope was named after US astronomer Edwin Hubble. Hubble was launched into orbit in 1990.

Over the next fifteen years, the orbiting telescope captured more than a million images of twenty-two thousand cosmic bodies, including galaxies, planets, stars and nebulae. A unique telescope took pictures and transmitted them to Earth.

Types of telescopes

Optical telescopes can operate with different types of focusing element. Accordingly, they are divided into refractors (lens) and reflectors (mirror).

A refracting telescope has a lens on the front side of the tube and an eyepiece at the back. The lens of such a telescope is usually a composite lens of several elements with a large focal length. The world's largest refractor has a lens with a diameter of 101 cm.

The reflector has a concave mirror instead of a lens, which is located at the back of the pipe. All large astronomical telescopes are reflective. Amateurs also use reflectors - this equipment is not as expensive as a refractor, and you can assemble it yourself.

In such a telescope, light is collected at a point in front of the primary mirror (primary focus), and then, through the secondary mirror, is directed to a place more convenient for work. There are several generally accepted focusing systems: Newtonian focus, Cassegrain focus, Coudet focus, Nesmith focus.

In large telescopes, the observer can work at the primary focus in a special booth installed in the main tube. Multipurpose professional telescopes are designed in such a way that the observer can choose the focus. Newtonian focus is used only in amateur optical telescopes.

The primary mirrors in reflectors are usually made of glass or ceramic, which does not respond to temperature changes. The surface of the mirror is processed to obtain a spherical or parabolic shape.

To obtain reflective properties, a thin layer of aluminum is applied to the surface. The Latin word for “reflective” is “speculum”, so the abbreviation “spec” is still sometimes used to refer to a reflecting telescope.

The James Webb Telescope is an orbital infrared observatory that should replace the famous Hubble Space Telescope.

This is a very complex mechanism. Work on it has been going on for about 20 years! The James Webb will have a composite mirror 6.5 meters in diameter and cost about $6.8 billion. For comparison, the diameter of the Hubble mirror is “only” 2.4 meters.

Let's see?

1. The James Webb telescope should be placed in a halo orbit at the Lagrange point L2 of the Sun-Earth system. And it's cold in space. Shown here are tests conducted on March 30, 2012, to examine the ability to withstand the cold temperatures of the space. (Photo by Chris Gunn | NASA):

2. The James Webb will have a composite mirror 6.5 meters in diameter with a collecting surface area of 25 m². Is this a lot or a little? (Photo by Chris Gunn):

3. Compare with Hubble. Hubble (left) and Webb (right) mirrors on the same scale:

4. Full-scale model of the James Webb Space Telescope in Austin, Texas, March 8, 2013. (Photo by Chris Gunn):

5. The telescope project is an international collaboration of 17 countries, led by NASA, with significant contributions from the European and Canadian Space Agencies. (Photo by Chris Gunn):

Full-scale model of the James Webb Space Telescope in Austin

6. Initially, the launch was planned for 2007, but was later postponed to 2014 and 2015. However, the first segment of the mirror was installed on the telescope only at the end of 2015, and the main composite mirror was not fully assembled until February 2016. (Photo by Chris Gunn):

7. The sensitivity of a telescope and its resolution are directly related to the size of the mirror area that collects light from objects. Scientists and engineers have determined that the minimum diameter of the primary mirror must be 6.5 meters in order to measure light from the most distant galaxies.

Simply making a mirror similar to that of the Hubble telescope, but larger, was unacceptable, since its mass would be too large to launch the telescope into space. The team of scientists and engineers needed to find a solution so that the new mirror would have 1/10 the mass of the Hubble telescope mirror per unit area. (Photo by Chris Gunn):

8. Not only here everything becomes more expensive from the initial estimate. Thus, the cost of the James Webb telescope exceeded the original estimates by at least 4 times. The telescope was planned to cost $1.6 billion and be launched in 2011, but according to new estimates, the cost could be $6.8 billion, with the launch not taking place earlier than 2018. (Photo by Chris Gunn):

9. This is a near-infrared spectrograph. It will analyze a range of sources, which will provide information about both the physical properties of the objects under study (for example, temperature and mass) and their chemical composition. (Photo by Chris Gunn):

Sun screen tests

The telescope will make it possible to detect relatively cold exoplanets with a surface temperature of up to 300 K (which is almost equal to the temperature of the Earth’s surface), located further than 12 AU. that is, from their stars, and distant from Earth at a distance of up to 15 light years. More than two dozen stars closest to the Sun will fall into the detailed observation zone. Thanks to James Webb, a real breakthrough in exoplanetology is expected - the capabilities of the telescope will be sufficient not only to detect the exoplanets themselves, but even the satellites and spectral lines of these planets.

11. Engineers test in the chamber. telescope lift system, September 9, 2014. (Photo by Chris Gunn):

12. Research of mirrors, September 29, 2014. The hexagonal shape of the segments was not chosen by chance. It has a high fill factor and has sixth order symmetry. A high fill factor means that the segments fit together without gaps. Thanks to symmetry, the 18 mirror segments can be divided into three groups, in each of which the segment settings are identical. Finally, it is desirable that the mirror has a shape close to circular - to focus the light on the detectors as compactly as possible. An oval mirror, for example, would produce an elongated image, while a square one would send a lot of light from the central area. (Photo by Chris Gunn):

Mirror Research

13. Cleaning the mirror with carbon dioxide dry ice. Nobody rubs with rags here. (Photo by Chris Gunn):

Cleaning a Mirror with Carbon Dioxide Dry Ice

14. Chamber A is a giant vacuum test chamber that will simulate outer space during testing of the James Webb Telescope, May 20, 2015. (Photo by Chris Gunn):

17. The size of each of the 18 hexagonal segments of the mirror is 1.32 meters from edge to edge. (Photo by Chris Gunn):

18. The mass of the mirror itself in each segment is 20 kg, and the mass of the entire assembled segment is 40 kg. (Photo by Chris Gunn):

19. A special type of beryllium is used for the mirror of the James Webb telescope. It is a fine powder. The powder is placed in a stainless steel container and pressed into a flat shape. Once the steel container is removed, the beryllium piece is cut in half to make two mirror blanks about 1.3 meters across. Each mirror blank is used to create one segment. (Photo by Chris Gunn):

20. Then the surface of each mirror is ground down to give it a shape close to the calculated one. After this, the mirror is carefully smoothed and polished. This process is repeated until the shape of the mirror segment is close to ideal. Next, the segment is cooled to a temperature of −240 °C, and the dimensions of the segment are measured using a laser interferometer. Then the mirror, taking into account the information received, undergoes final polishing. (Photo by Chris Gunn):

21. Once the segment is processed, the front of the mirror is coated with a thin layer of gold to better reflect infrared radiation in the range of 0.6-29 microns, and the finished segment is re-tested at cryogenic temperatures. (Photo by Chris Gunn):

22. Work on the telescope in November 2016. (Photo by Chris Gunn):

23. NASA completed assembly of the James Webb Space Telescope in 2016 and began testing it. This is a photo from March 5, 2017. At long exposures, the techniques look like ghosts. (Photo by Chris Gunn):

Transporting the telescope to Houston

26. The door to the same chamber A from the 14th photograph, in which outer space is simulated. (Photo by Chris Gunn):

James Webb Telescope inside Chamber A