Types of telescopes. An optical telescope is designed for... Optical telescopes. The invention of Galileo's telescope What does a telescope give to a person

How to see the Moon through a telescope

Telescopes
The Russian market can provide consumers with a variety of telescopes designed for use by both ordinary amateurs and professionals. To observe celestial bodies, you need to buy telescopes that are easy to use. They must be functional and well equipped.

Key product characteristics
Modern telescopes have quite a lot of functions. Some astronomers are more interested in special functions, others - ease of control of the device, and others - ease of use. Therefore, you need to pay attention to the key parameters of the equipment in order to choose the optimal telescope.

For beginners, we recommend the Meade DS2080AT-TC model. She has wide possibilities. Thanks to the " guide"(she is on the control panel) the telescope turns on automatic aiming, which allows the device to quickly find interesting celestial bodies. By observing them, the amateur astronomer will also receive information about them. The device is easy to operate, and the tripod allows you to place the telescope so that it is convenient to view celestial bodies.

For novice astronomers, we can recommend the Celestron LCM 80, equipped with SkyAlign technology and computer control. Thanks to this, the telescope can be set up for operation extremely quickly. Objects are selected in the sky, and then the telescope will conduct research. Experienced specialists consider such a system optimal at the initial stage of work. 4,000 objects are stored in the memory of this telescope, and the user can add 40 more.

If you often travel outdoors, we recommend purchasing the Vixen Greet Polaris ED 81SF mobile model. The compact product has an unusual and stylish design. The design of such a device allows the product to be transported safely and very easily. The lenses of this telescope are made of glass with extremely low dispersion, so image distortion will be minimal. The resulting picture will be incredibly bright, as clear as possible and incredibly contrasty.

Now let's see what telescopes are available in general terms:

» Children's telescopes
This is a great gift for curious preschoolers. They are extremely easy to use and extremely colorful. Usually supplied as a set, which also includes encyclopedias, toy models and other assortment. The design and functionality of the device fully corresponds to the target audience.

» Refracting telescopes
Most novice astronomers purchase such cheap models. In such telescopes, lenses assembled into an objective are used for magnification. Yes, it is unlikely that with their help astronomers will be able to observe distant celestial bodies, but they will be able to study the Moon and planets in detail.

» Reflecting telescopes
Reflecting telescopes, which use mirrors instead of lenses, are more expensive. This allows you to dramatically increase the magnification factor. Therefore, you can consider comets, star clusters, and asteroids. In short, everything that cannot be observed with the previous telescope. There is also a catadioptric telescope, which uses lenses and mirrors at the same time.

» Helioscopes
A helioscope is used to observe the sun. Colored and smoked glasses were used as filters. Then they began to use more sophisticated filters. However, today such devices are irrelevant, because more advanced products are already being produced.

» Coronagraphs
This device also observes the sun, but only its corona. True, during eclipses a regular telescope is suitable for such purposes, but the rest of the time special equipment is needed.

» Radio telescopes and other products
Radio telescopes are intended for those working in desert areas. They consist of an antenna and a radiometer that amplifies the signals. There are also gravitational and space telescopes. This is already for professionals.

Conclusion
Here is a short article about telescopes. As you can see, there are fantastically many varieties. And this is only a small part. It is possible that our article will help you purchase a device that will be easy to use and fully equipped.

And finally the video: “ The James Webb Space Telescope is an orbiting infrared observatory, a new generation telescope, the successor to the famous Hubble. One of the most expensive scientific projects of our time. If it is launched into space, which will not happen until 2018, it will become the most advanced, largest and most powerful space telescope that humanity has ever sent into space.»

In this section we tried to put together the fragmentary information that can be found on the Internet. There is a lot of information, but it is not systematized and scattered. We, guided by many years of experience, have systematized our knowledge in order to simplify the choice for novice astronomy lovers.

Main characteristics of telescopes:

Typically, the name of a telescope indicates its focal length, lens diameter, and mount type.
For example, Sky-Watcher BK 707AZ2, where the lens diameter is 70 mm, the focal length is 700 mm, the mount is azimuth, second generation.
However, the focal length is often not indicated on the telescope labeling.
For example Celestron AstroMaster 130 EQ.

A telescope is a more versatile optical instrument than a spotting scope. A larger range of magnifications is available to him. The maximum available magnification is determined by the focal length (the longer the focal length, the greater the magnification).

To display a clear and detailed image at high magnification, the telescope must have a large diameter lens (aperture). The bigger, the better. A large lens increases the telescope's aperture and allows you to view distant objects of low luminosity. But as the diameter of the lens increases, the dimensions of the telescope also increase, so it is important to understand under what conditions and for observing what objects you want to use it.

How to calculate the magnification of a telescope?

Changing the magnification in a telescope is achieved by using eyepieces with different focal lengths. To calculate the magnification, you need to divide the focal length of the telescope by the focal length of the eyepiece (for example, the Sky-Watcher BK 707AZ2 telescope with a 10 mm eyepiece will give a magnification of 70x).

The multiplicity cannot be increased indefinitely. As soon as the magnification exceeds the resolving power of the telescope (lens diameter x1.4), the image becomes dark and blurry. For example, a Celestron Powerseeker 60 AZ telescope with a focal length of 700 mm does not make sense to use with a 4 mm eyepiece, because in this case it will give a magnification of 175x, which is significantly greater than 1.4 times the diameter of the telescope - 84).

Common mistakes when choosing a telescope

• The higher the multiplicity, the better
  This is far from true and depends on how and under what conditions the telescope will be used, as well as on its aperture (lens diameter).
  If you are a beginner astronomer, you should not chase high magnification. Observing distant objects requires a high degree of training, knowledge and skill in astronomy. The Moon and planets of the solar system can be observed at magnifications from 20 to 100x.
• Buying a reflector or large refractor for observations from a balcony or from a city apartment window
  Reflectors (mirror telescopes) are very sensitive to atmospheric fluctuations and to extraneous light sources, so it is extremely impractical to use them in urban conditions. Large aperture refractors (lens telescopes) always have a very long tube (for example, with an aperture of 90 mm, the length of the tube will exceed 1 meter), so their use in city apartments is not possible.
• Buying a telescope with an equatorial mount as your first
  The equatorial mount is quite difficult to master and requires some training and qualifications. If you are a beginner astronomer, we would recommend purchasing a telescope on an alt-azimuth mount or a Dobsonian mount.
• Buying cheap eyepieces for serious telescopes and vice versa
  The quality of the resulting image is determined by the quality of all optical elements. Installing a cheap eyepiece made from budget optical glass will negatively affect image quality. Conversely, installing a professional eyepiece on an inexpensive device will not lead to the desired result.

FAQ

• I want a telescope. Which one should I buy?
  A telescope is not something you can buy without any purpose. A lot depends on what you plan to do with it. Telescope capabilities: show both terrestrial objects and the Moon, as well as galaxies hundreds of light years away (only the light from them takes years to reach the Earth). The optical design of the telescope also depends on this. Therefore, you must first decide on an acceptable price and object of observation.
• I want to buy a telescope for my child. Which one should I buy?
  Many manufacturers have introduced children's telescopes into their range especially for children. This is not a toy, but a full-fledged telescope, usually a long-focus achromatic refractor on an azimuthal mount: it is easy to install and configure, it will show the Moon and planets well. Such telescopes are not very powerful, but they are inexpensive, and there is always time to buy a more serious telescope for a child. If, of course, the child is interested in astronomy.
• I want to look at the moon.
  You will need a telescope “for near space.” In terms of optical design, long-focus refractors, as well as long-focus reflectors and mirror-lens telescopes, are best suited. Choose a telescope of these types to suit your taste, based on price and other parameters you need. By the way, through such telescopes it will be possible to look not only at the Moon, but also at the planets of the solar system.
• I want to look at distant space: nebulae, stars.
  Any refractors, short-focus reflectors and mirror-lens telescopes are suitable for these purposes. Choose according to your taste. And some types of telescopes are equally well suited for both near space and far space: these are long-focus refractors and mirror-lens telescopes.
• I want a telescope that can do everything.
  We recommend reflex lens telescopes. They are good for ground-based observations, for the Solar System, and for deep space. Many of these telescopes have simpler mounts and computer guidance, and are a great option for beginners. But such telescopes have a higher price than lens or mirror models. If price is a factor, you might want to look at a long-focus refractor. For beginners, it is better to choose an alt-azimuth mount: it is easier to use.
• What is a refractor and reflector? Which is better?
  Telescopes of various optical designs will help you visually get closer to the stars; the results are similar, but the mechanisms of the device are different and, accordingly, the application features are different.
  A refractor is a telescope that uses optical glass lenses. Refractors are cheaper, they have a closed tube (no dust or moisture will get into it). But the tube of such a telescope is longer: these are the structural features.
  The reflector uses a mirror. Such telescopes are more expensive, but they have smaller dimensions (shorter tube). However, the telescope mirror may fade over time and the telescope may become blind.
  Any telescope has its pros and cons, but for any task and budget you can find the ideal telescope model. Although, if we talk about the choice in general, mirror-lens telescopes are more versatile.
• What is important when buying a telescope?
  Focal length and lens diameter (aperture).
  The larger the telescope tube, the larger the lens diameter will be. The larger the lens diameter, the more light the telescope will collect. The more light the telescope collects, the better dim objects will be visible and the more details will be visible. This parameter is measured in millimeters or inches.
  Focal length is a parameter that affects the magnification of a telescope. If it is short (up to 7), it will be harder to get a large increase. A long focal length starts at 8 units; such a telescope will magnify more, but the viewing angle will be smaller.
  This means that to observe the Moon and planets, a higher magnification is needed. Aperture (as an important parameter for the amount of light) is important, but these objects are already quite bright. But for galaxies and nebulae, it is the amount of light and aperture that are most important.
• What is the magnification of a telescope?
  Telescopes visually magnify an object so much that you can see details on it. The magnification will show how much you can visually enlarge something at which the observer’s gaze is directed.
  The magnification of a telescope is largely limited by its aperture, that is, by the boundaries of the lens. In addition, the higher the magnification of the telescope, the darker the image will be, so the aperture must be large.
  The formula for calculating magnification is: F (lens focal length) divided by f (eyepiece focal length). One telescope usually comes with several eyepieces, and the magnification ratio can thus be changed.
• What can I see with a telescope?
  This depends on telescope characteristics such as aperture and magnification.
  So:
  aperture 60-80 mm, magnification 30-125x - lunar craters from 7 km in diameter, star clusters, bright nebulae;
  aperture 80-90 mm, magnification up to 200x - phases of Mercury, lunar grooves 5.5 km in diameter, rings and satellites of Saturn;
  aperture 100-125 mm, magnification up to 300x - lunar craters from 3 km in diameter, clouds of Mars, stellar galaxies and nearby planets;
  aperture 200 mm, magnification up to 400x - lunar craters from 1.8 km in diameter, dust storms on Mars;
  aperture 250 mm, magnification up to 600x - satellites of Mars, details of the lunar surface from 1.5 km in size, constellations and galaxies.
• What is a Barlow lens?
  Additional optical element for a telescope. In fact, it increases the telescope's magnification several times, increasing the focal length of the lens.
  The Barlow lens does work, but its capabilities are not unlimited: the lens has a physical limit to its useful magnification. After overcoming it, the image will really become larger, but the details will not be visible, only a large cloudy spot will be visible in the telescope.
• What is a mount? Which mount is better?
  A telescope mount is the base on which the tube is mounted. The mount supports the telescope, and its specially designed mount allows you not to rigidly mount the telescope, but also to move it along different trajectories. This will be useful, for example, if you need to monitor the movement of a celestial body.
  The mount is just as important for observing as the main part of the telescope. A good mount should be stable, balance the pipe and fix it in the desired position.
  There are several types of mounts: azimuth (lighter and easier to set up, but difficult to keep the star in the field of view), equatorial (more difficult to set up, heavier), Dobson (a type of azimuth for floor installation), GoTo (self-guided telescope mount, you just need to enter the target ).
  We do not recommend the equatorial mount for beginners: it is difficult to set up and use. Azimuthal for beginners - just right.
• There are Maksutov-Cassegrain and Schmidt-Cassegrain mirror-lens telescopes. Which is better?
  From the point of view of application, they are approximately the same: they will show both near space, and distant, and ground objects. The difference between them is not so significant.
  Due to their design, Maksutov-Cassegrain telescopes do not have side glare and their focal length is longer. Such models are considered preferable for studying planets (although this statement is practically disputed). But they will need a little more time for thermal stabilization (starting to work in hot or cold conditions, when you need to equalize the temperature of the telescope and the environment), and they weigh a little more.
  Schmidt-Cassegrain telescopes will require less time for thermal stabilization and will weigh a little less. But they have side glare, a shorter focal length, and less contrast.
• Why are filters needed?
  Filters will be needed by those who want to take a closer look at the object of study and examine it better. As a rule, these are people who have already decided on a goal: near space or distant space.
  There are planetary filters and deep space filters, which are optimal for studying the target. Planetary filters (for planets of the Solar System) are optimally selected in order to view a particular planet in detail, without distortion and with the best contrast. Deep sky filters (for deep space) will allow you to focus on a distant object. There are also filters for the Moon, so that you can view the earth’s satellite in all detail and with maximum convenience. There are also filters for the Sun, but we would not recommend observing the Sun through a telescope without proper theoretical and material preparation: for an inexperienced astronomer there is a high risk of vision loss.
• Which manufacturer is better?
  From what is presented in our store, we recommend paying attention to Celestron, Levenhuk, Sky-Watcher. There are simple models for beginners and separate additional accessories.
• What can you buy in addition to the telescope?
  There are options, and they depend on the wishes of the owner.
  Light filters for planets or deep space - for better results and image quality.
  Adapters for astrophotography - for documenting what you were able to see through the telescope.
  A backpack or carrying bag - for transporting the telescope to the observation site, if it is remote. The backpack will protect fragile parts from damage and not lose small items.
  Eyepieces - the optical designs of modern eyepieces differ; accordingly, the eyepieces themselves differ in price, viewing angle, weight, quality, and most importantly - focal length (and the final magnification of the telescope depends on it).
  Of course, before making such purchases, it is worth checking whether the add-on is suitable for the telescope.
• Where should you look through a telescope?
  Ideally, to work with a telescope, you need a place with a minimum of lighting (city illumination from street lamps, illuminated advertising, light from residential buildings). If there is no known safe place outside the city, you can find a place within the city, but in a fairly dimly lit place. Clear weather will be required for any observations. It is recommended to observe deep space during the new moon (give or take a few days). A weak telescope will need a full moon - it will still be difficult to see anything further than the Moon.

Basic criteria when choosing a telescope

Optical design. Telescopes come in mirror (reflector), lens (refractor) and mirror-lens types.
Lens diameter (aperture). The larger the diameter, the greater the telescope's aperture and its resolution. Moreover, the more distant and dim objects can be seen through it. On the other hand, diameter greatly influences the dimensions and weight of a telescope (especially a lens one). It is important to remember that the maximum useful magnification of a telescope cannot physically exceed 1.4 times its diameter. Those. with a diameter of 70 mm, the maximum useful magnification of such a telescope will be ~98x.
Focal length— how far the telescope can focus. A long focal length (long focal length telescopes) means higher magnification, but a smaller field of view and aperture ratio. Suitable for detailed viewing of small, distant objects. A short focal length (short-focus telescopes) means low magnification but a large field of view. Suitable for observing extended objects such as galaxies and astrophotography.
Mount is a method of attaching a telescope to a tripod. Azimuthal (AZ) - rotates freely in two planes like a photo tripod. Equatorial (EQ) is a more complex mount that is adjusted to the celestial pole and allows you to find celestial objects knowing their hour angle. A Dobsonian mount is a type of azimuth mount, but it is more suitable for astronomical observations and allows larger telescopes to be mounted on it. Automated - computerized mount for automatic targeting of celestial objects, uses GPS.

Pros and cons of optical circuits

Long-focus achromat refractors (lens optical system)

Short-focus achromat refractors (lens optical system)

Long-focus reflectors (mirror optical system)

Short throw reflectors (mirror optical system)

Mirror-lens optical system (catadioptric)

Schmidt-Cassegrain (a type of mirror-lens optical design)

Maksutov-Cassegrain (a type of mirror-lens optical design)

What can you see through a telescope?

Aperture 60-80 mm
Lunar craters from 7 km in diameter, star clusters, bright nebulae.

Aperture 80-90 mm
Phases of Mercury, lunar grooves 5.5 km in diameter, rings and satellites of Saturn.

Aperture 100-125 mm
Lunar craters from 3 km to study the clouds of Mars, hundreds of star galaxies, nearby planets.

Aperture 200 mm
Lunar craters 1.8 km, dust storms on Mars.

Aperture 250 mm
Satellites of Mars, details of the lunar surface 1.5 km, thousands of constellations and galaxies with the ability to study their structure.

26.10.2017 05:25 2876

What is a telescope and why is it needed?

A telescope is a device that allows you to view space objects at close range. Tele is translated from ancient Greek - far, and skopeo - I look. Externally, many telescopes are very similar to a spyglass, so they have the same purpose - to bring images of objects closer. Because of this, they are also called optical telescopes because they magnify images using lenses, optical materials similar to glass.

The birthplace of the telescope is Holland. In 1608, spectacle makers in this country invented the spotting scope, the prototype of the modern telescope.

However, the first drawings of telescopes were discovered in the documents of the Italian artist and inventor Leonardo da Vinci. They bore the date 1509.

Modern telescopes are placed on a special stand for greater convenience and stability. Their main parts are the lens and the eyepiece.

The lens is located in the part of the telescope farthest from the person. It contains lenses or concave mirrors, so optical telescopes are divided into lens and mirror telescopes.

The eyepiece is located in the part of the device closest to the person and faces the eye. It also consists of lenses that magnify the image of objects formed by the lens. Some modern telescopes used by astronomers have a display instead of an eyepiece that shows images of cosmic objects.

Professional telescopes differ from amateur telescopes in that they have greater magnification. With their help, astronomers were able to make many discoveries. Scientists conduct observations at observatories of other planets, comets, asteroids and black holes.

Thanks to telescopes, they were able to study in more detail the Earth's satellite, the Moon, which is located at a relatively small distance by cosmic standards from our planet - 384,403 km. The magnification of this device allows you to clearly see the craters of the lunar surface.

Amateur telescopes are sold in stores. In terms of their characteristics, they are inferior to those used by scientists. But with their help you can also see the craters of the Moon,

OPTICAL TELESCOPE

OPTICAL TELESCOPE - used to obtain images and spectra of space. objects in optical range. electron-optical converters, charge-coupled devices. The efficiency of an optical telescope is the magnitude achievable on a given telescope for a given signal-to-noise ratio (accuracy). For weak point objects, when determined by the background of the night sky, it depends mainly. from attitude D/,Where D- aperture size O. t., - ang. diameter of the image it produces (the larger D/,the greater, all other things being equal, is the limiting magnitude). Operating at optimum. O. t. conditions with a mirror diam. 3.6 m has a maximum stellar magnitude of approx. 26 T with an accuracy of 30%. There are no fundamental restrictions on the maximum stellar magnitude of terrestrial stars.
Astr. O. t. was invented by G. Galilei in the beginning. 17th century (although he may have had predecessors). HisO. i.e. had a scattering (negative) . Approx. in the same I. sighting accuracy. Throughout the 17th century. Astronomers used optical telescopes of a similar type with a lens consisting of a single flat-convex lens. With the help of these orbitals, the surface of the Sun (spots, torches) was studied, the Moon was mapped, the satellites of Jupiter and the reflector were discovered. With the help of similar orbitals, W. Herschel discovered Uranus. Progress of glass making and optical theory. systems made it possible to create in the beginning. 19th century achromatic Achromat). The optical telescopes using them (refractors) were relatively short in length and gave a good image. Using such optical telescopes, distances to the nearest stars were measured. Similar tools are still used today. The creation of a very large (with a lens diameter of more than 1 m) lens refractor turned out to be impossible due to the deformation of the lens under the influence of its own. weight. Therefore, in con. 19th century The first improved reflectors appeared, which consisted of a concave parabolic made of glass. shape, coated with a reflective layer of silver. With the help of similar O. t. in the beginning. 20th century Distances to nearby galaxies were measured and cosmological discoveries were made. redshift.
The basis of optical technology is its optics. system. A). Optical option system is the Cassegrain system: a beam of converging rays from Ch. parabolic the mirror is intercepted to focus by a convex hyperbolic. mirror (Fig. b). Sometimes this focus is carried out into a stationary room (where) with the help of mirrors. Working field of view, within the optical range. modern system large O. t. builds undistorted images, does not exceed 1 - 1.5°. The wider-angle O. surface is placed at the center of curvature of the spherical surface. mirrors Maksutov systems have aberrations (see. Aberrations of optical systems)ch. spherical mirrors are corrected by a meniscus with a spherical field of view up to 6°. The material from which O. t. mirrors are made has low thermal properties. coefficient expansion (TCR) so that the shape of the mirror does not change when the temperature changes during observations.

Reflecting telescopes take advantage of the fact that shaped mirrors produce results very similar to lenses. Reflecting telescopes suffer from another kind of distortion called spherical aberration, where light rays from different locations are focused at different points. This is because the surface is spherical, hence the name. Although it can be difficult, this aberration can be eliminated by adjusting the mirror to a perfect parabolic shape.

Catadioptric telescopes use a mixture of lenses and mirrors to maximize light collection and minimize telescope distortion. An optical telescope collects light and focuses it to form an image. Astronomers use telescopes that cover the entire electromagnetic spectrum, but the first telescopes were purely optical telescopes. Galileo was the first known scientist to use a telescope for astronomy; Before his time, our ability to produce high-quality lenses was insufficient to create such a telescope.

Some optical designs of large modern reflectors: A- direct focus; b- Cassegrain trick. A- main mirror, IN - focal surface, arrows indicate the path of rays.

Optical elements of the O.T. are fixed in the O. pipe. t. To eliminate decentration of optics and prevent deterioration in image quality when the pipe is deformed under the influence of the weight of parts of optical t. n. compensation pipes type that do not change the direction of the optical fiber when deformed. Installation (mounting) of the O.T. allows you to point it at a selected cosmic location. object and accurately and smoothly accompany this object in its daily movement across the sky. The equatorial mount is widespread: one of the axes of rotation of the O. t. (polar) is directed towards the world (see. Astronomical coordinates) and the second is perpendicular to it. In this case, the object is tracked in one motion - rotation around the polar axis. With an azimuth mount, one of the axes is vertical (computer) - by turning in azimuth and height and rotating the photographic plate (receiver) around the optical. axes. An azimuthal mount makes it possible to reduce the mass of the moving parts of the pipe, since in this case the pipe rotates relative to the gravity vector in only one direction. O. t. installed in special. towers. The tower must be in thermal equilibrium with the environment and with the telescope. Modern O. t. can be divided into four generations. The 1st generation includes reflectors with a main glass (TKR 7x 10 -6) parabolic mirror. shapes with a thickness to diameter ratio (relative thickness) of 1/8. The tricks are direct, Cassegrain and coude. The pipe - solid or lattice - is made according to the principle of max. rigidity. O. t. of the 2nd generation is also characterized by parabolic. Ch. mirror. Tricks - direct with corrector, Cassegrain and coude. The mirror is made of pyrex (glass with TKR reduced to 3 x10 -6), relates. thickness 1/8. Very rarely the mirror was made lightweight, i.e. it had voids on the back side. reflector of the Mount Palomar Observatory (USA, 1947) and a 2.6-meter reflector of the Crimean Astrophysics. Observatory (USSR, 1961).
O. t. 3rd generation began to be created at the end. 60s They are characterized by optical scheme with hyperbolic Ch. mirror (the so-called Ritchie-Chretien scheme). Focuses - direct with corrector, Cassegrain, quartz or glass-ceramic (TKR 5 x 10 -7 or 1x 10 -7), relative. thickness 1 / 8 . Pipe compensation scheme. Hydrostatic bearings. Example: 3.6-meter reflector of the European Southern Observatory (Chile, 1975).
O.t. 4th generation - instruments with mirror dia. 7 - 10 m; They are expected to enter service in the 90s. They involve the use of a group of innovations aimed at meaning. reducing the weight of the tool. Mirrors - made of quartz, glass-ceramic and, possibly, pyrex (lightweight). Refers. thickness less than 1/10. Compensation pipe. The world's largest telescope is a 6-meter telescope installed in the Special. astrophysics observatory (SAO) of the USSR Academy of Sciences in the North Caucasus. The telescope has a direct focus, two Nasmyth focuses and a focuskude. The mount is azimuth.
O. t., consisting of several, have a well-known perspective. mirrors, the light from which is collected in a common focus. One of these O. t. operates in the USA. It consists of six 1.8-meter parabolics. Solar telescopes are characterized by very large spectral equipment, which is why the mirrors are usually made motionless, and the light of the Sun is applied to them by a system of mirrors called a coelostat. Diameter modern solar O. t. is usually 50 - 100 cm. Astrometric. O. t. (intended to determine the positions of space objects) are usually small in size and higher. mechanical stability. O.t. for photography astrometry have special. To eliminate the influence of the atmosphere, it is planned to install O. t. in space. devices.

There are three types of telescopes: refractive, reflective and catadioptric. Refracting telescopes use lenses to focus light, reflecting telescopes use curved mirrors, and catadioptic telescopes use a mixture of both. Refracting telescopes may suffer from chromatic aberration, and reflecting telescopes may suffer from spherical aberration. In both cases, the image becomes blurry. Chromatic aberration can be corrected using multiple lenses, while spherical aberration can be corrected using a parabolic mirror.

Lit.: Methods of astronomy, trans. English, M., 1967; Shcheglov P.V., Problems of optical astronomy, M., 1980; Optical telescopes of the future, trans. from English, M., 1981; Optical and infrared telescopes of the 90s, trans. from English, M., 1983.

P. V. Shcheglov.

Physical encyclopedia. In 5 volumes. - M.: Soviet Encyclopedia. Editor-in-chief A. M. Prokhorov. 1988 .

What a person sees with the eyes depends on the resolution that can be achieved on the human retina. However, this is not always satisfactory. For this reason, since ancient times, milled rock crystals have been used as so-called "Lesstein" to compensate for transparency due to old age and to serve as a magnifying glass.

The development of such materials in high quality and in any quantity of detail was largely a material development of glass for the production of "lenses" - as these optical components were soon named because of the typical geometry - a story unto itself. The same applies to its processing and finishing by grinding and polishing.

- (Greek, this. See telescope). An optical instrument, a telescope, with the help of which objects located at a far distance are examined; used more for astronomical observations. Dictionary of foreign words included in... ...

- (from the word optics). Related to light, to optics. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. OPTICAL from the word optics. Relating to light. Explanation of 25,000 foreign words that came into use in... ... Dictionary of foreign words of the Russian language

Therefore, the path to an optical telescope is directly related to the development of reading tools. Especially from the beginning to the end of the century, glasses can make good progress, as evidenced by archaeological finds. Nearsightedness was primarily disadvantaged because the concave lenses needed to correct this type of defective vision were difficult to manufacture to satisfactory quality, unlike convex ones.

The question remains as to who first held a strong concave lens close to the eye and a weak convex lens at some distance one after the other and thus discovered the basic principle of the telescope. This year he proposed the first such tubular liner combination to Dutch authorities as a weapon-defining tool. At this time, the Netherlands was fighting for independence, and its fighters were interested in being able to observe the enemy from a great distance without being exposed to risk.

telescope- a, m. telescope m., n. lat. telescopium gr. far seeing. 1. An optical device for observing celestial bodies. BAS 1. Late in the evening he was walking... he had a hand telescope in his hand, he stopped and took aim at some planet: it was puzzling... Historical Dictionary of Gallicisms of the Russian Language

However, the patent was suspended because two other Dutch glasses, Zacharias Janssen and Jakob Adriaanzoon Metius, appeared at the same time. Although at first only distant objects were discovered on earth, it took a short time for naturalists to also turn to the skies.

His improvement proposals, and those of his contemporaries and successors, aimed to improve the telescope's usability, resolution, and image quality. Their constant implementation resulted in the fact that celestial bodies were always more closely observed and that the interactions between individual astronomical objects could be studied more and more precisely. This ultimately revolutionized man's self-awareness in space and led to interpretations that are now commonplace: be it the acceptance of a heliocentric worldview, the number of planets and satellites in our solar system, or the fact that our sun is just one of an unimaginably many stars are again located in one of the billions of galaxies.

TELESCOPE (Telescopium), a faintly visible constellation in the Southern Hemisphere. The brightest star is Alpha, 3.5 magnitude. TELESCOPE, a device for obtaining magnified images of distant objects or studying electromagnetic radiation from ... ... Scientific and technical encyclopedic dictionary

A device in which standing or running electricity can be excited. mag. optical waves range. O. r. is a collection of several mirrors and phenomena open resonator, unlike most cavity resonators used in the range... ... Physical encyclopedia

The road to this realization was wide and posed many technical challenges. Since the invention of the telescope, all its components have been experimented with, their limits recognized and improved. The following sections briefly describe selected developments in this area.

The key elements here are the components that direct and collect the light, the measuring instruments and receivers that capture and record that light, and the mechanical components that house or advantageously organize the optics and detectors.

TELESCOPE- An optical instrument that helps the eye or camera to observe or photograph distant objects, magnify celestial bodies and focus the flow of light, increasing the clarity of the image. From some ancient reports it can be concluded that the telescope... ... Astrological encyclopedia

Optical telescopes are divided into two categories: lens telescopes and reflecting telescopes. Both telescopes were invented at the beginning of the century, but the telescope was about ten years earlier than the reflecting telescope. Today, refractors are essentially used only by hobby astronomers, while all scientifically used telescopes, and large telescopes in particular, are reflectors.

Lens Reflectors A refractor consists of two lenses: an objective lens, a collection lens, and an eyepiece, depending on the design, a collection lens, or a diverging lens. The Kepler telescope of two collectible lenses is a common design of modern refractors, the image rotated 180 degrees is often properly aligned by additional optical elements. Objective telescopes have two very important disadvantages: on the one hand, the dependence of the refractive index on the wavelength leads to an aberration error, chromatic aberration: light beams of different wavelengths converge at different coordination points.

Telescope (from tele... and Greek: skopéo I look), an astronomical optical instrument designed for observing celestial bodies. According to their optical design, telescopes are divided into mirror (reflectors), lens (refractors) and mirror-lens... ... Great Soviet Encyclopedia

TELESCOPE, telescope, man. (from the Greek tele into the distance and skopeo I look). 1. Optical instrument for observing celestial bodies (astron.). 2. A fish of a reddish-golden color with extremely bulging eyes (zool.). Ushakov's explanatory dictionary. D.N. Ushakov... ... Ushakov's Explanatory Dictionary

This effect can be reduced by increasing the focal length of the lenses. This resulted in the last large refractors being extremely large and therefore difficult to handle at the end of the century. On the other hand, lenses of any size cannot be used.

Large lenses are very heavy and difficult to mount and stabilize due to their weight and because they can only be attached to the edge. The technical limit is about one meter. Mirror Telescopes After the technical limits of telescopes lenses were reached towards the end of the century, mirror telescopes finally released them because they are not subject to the same aperture limitation, and in the case of mirrors, chromatic aberration does not occur. A reflecting telescope essentially consists of two mirrors: the main or main mirror and the catch or some of these designs are shown in the following.

If you are a “typical” astronomy enthusiast who owns a telescope, then you have probably asked yourself more than once: how high-quality images does it show? There are many products on sale whose quality is easy to evaluate. If, say, you are offered to buy a car that cannot accelerate faster than 20 km/h, you will immediately realize that there is something “wrong” with it. But what about a newly purchased or assembled telescope, how do you know if its optics are “working” at full power? Will it ever be able to demonstrate the kinds of celestial objects you expect from it?

The telescope on the roof of the Göttingen Institute for Astrophysics is a Cassegrain telescope. Since light does not penetrate the mirror, the entire underside can be used for mounting. Therefore, in principle, the size of the mirror is not subject to any size limitation. The largest two-piece mirror with a diameter of 8.4 meters is the Large Binocular Telescope. Larger mirror diameters are achieved through segmentation. The Hobby-Eberly Telescope mirror, for example, consists of 91 hexagonal elements with a diameter of one meter and is actually equivalent to a 9.2-meter mirror.

Fortunately, there is a simple but very accurate way to test the quality of optics that does not require any special equipment. Just as you don't need to know the theory of an internal combustion engine to determine that an engine is running poorly, you don't need to be familiar with the theory of optical design to judge the quality of a telescope. By mastering the testing techniques discussed in this article, you can become an authoritative judge of optical quality.

The European Extremely Large Telescope is estimated to have an effective diameter of 42 meters. As in radio astronomy, interference is also a common method of optical observation. The four 8.2-meter telescopes of the Very Large Telescope can be interferometrically interconnected. The Hubble Space Telescope, undisturbed by the Earth's atmosphere, partially observes in the optical frequency range.

Installation In addition to the telescope itself, its installation is also necessary. The telescope must be very durable, but at the same time mobile. Maximum coverage of the visible sky requires two axes. In an equatorial mount or parallax mount, one of the two axes is aligned parallel to the Earth's axis of rotation. The rotation angle of the other axis then exactly corresponds to the declination of the observed object. This mount allows you to simply track the telescope to compensate for the Earth's rotation, which only requires rotation around its axis.

PERFECT IMAGE

Before you start talking about quality, you need to know what an ideal image of a star should look like through a telescope. Some novice astronomers believe that in an ideal telescope, a star should always appear as a bright and sharp point of light. However, it is not. When observed at high magnifications, the star appears as a small disk surrounded by a series of faint concentric rings. This is called a diffraction pattern. The central disk of the diffraction pattern has its own name and is called the Airy circle.

In this case, the facial field remains unchanged, so that long-term exposure to expanded objects can be made. On the other hand, the azimuth mount is more stable and is therefore used in particular in large telescopes. It has a vertical axis and a horizontal axis. Tracking is much more difficult because both axes must move at constantly changing speeds. This is, however, easily possible with computer controlled stepper motors. Rotation of the face field during tracking is inevitable.

Flat objects are thus washed out during long exposures. To avoid this, several short exposures must be made instead, and the individual images must be rotated before overlaying them. It is also necessary to take into account the installation of additional devices - also when choosing a telescopic type. Thus, the second axis is almost replaced by the rotation of the earth. However, the observable part of the sky is more limited.

This is what the diffraction pattern should look like in an ideal telescope. Please note that the diffraction rings look exactly the same on opposite sides of the focus. In telescopes that have a secondary mirror (screening), a dark area appears in the center of the defocused image. All illustrations shown in the article were simulated using a computer. In all illustrations, the image in the center is exactly in focus, the two on the left are in front of focus (closer to the lens), and the two on the right are behind focus (further from the lens).

A siderostat or heliostat allows light to be fed into a static telescope. The siderostat on the roof of the Göttingen Institute for Astrophysics consists of two rotating and rotating plan mirrors that direct the light of the sun and bright stars into a vertical telescope built into the building. The start of construction of the world's largest optical telescope has fallen: in the Atacama Desert in Chile, representatives of the European Southern Observatory and the Chilean government took part in a ceremony to begin construction.

With the help of a giant telescope it would also be possible to detect life in the Universe. The telescope will also yield new findings on dark matter. The festive hour was marred by a small problem. However, the construction of the telescope will not be delayed. The extremely large telescope has a mirror with a diameter of 39 meters. Currently, the largest telescopes have a maximum of ten-meter mirrors. A budget of one billion euros is estimated for the first phase of construction.

What causes these rings to appear and the star to turn into a disk? The answer to this question lies in the wave nature of light. When light passes through a telescope, it always experiences “distortions” caused by its design and optical system. Not a single most remarkable telescope in the world is able to reproduce the image of a star in the form of a point, since this contradicts the fundamental laws of physics. Laws that cannot be broken.

The accuracy of image reproduction produced by a telescope depends on its aperture - the diameter of the lens. The larger it is, the smaller the angular dimensions of the diffraction pattern and its central disk become. This is why telescopes with larger diameters can separate closer binary stars and allow us to see more detail on planets.

Let's conduct one experiment with which you can find out what the diffraction pattern of an almost ideal lens looks like. This image will become the standard with which you will subsequently compare the actual diffraction patterns of the instruments being tested. For the experiment to be successful, we will need a telescope with intact and fairly well-adjusted optics.

First of all, take a sheet of cardboard or thick paper and cut a round hole with a diameter of 2.5-5 cm in it. For telescopes with a focal length of the lens less than 750 mm, a hole of 2.5-3 cm is suitable; for a larger focal length of the lens, cut a hole with a diameter of 5 cm.

The resulting sheet of cardboard must be secured in front of the lens so that the hole, if you have a refractor, is in the center, and if you have a reflector, it is slightly on the edge, so that the incoming light passes the secondary mirror and the stretch marks of its attachment to the pipe.

Point the telescope at a bright star (such as Vega or Capella) that is currently high above the horizon, and set the magnification to 20 to 40 times the lens diameter in centimeters. Looking through the eyepiece, you will see a diffraction pattern - a spot of light surrounded, depending on the calmness of the atmosphere, by one or more concentric rings.

Now begin to slowly defocus the image of the star. At the same time, you will see expanding rings originating in the center of the light spot, just as waves diverge from a stone thrown into water. Defocus the image until you see 4-6 of these rings. Notice that the light is distributed more or less evenly across the rings.

Having memorized the type of diffraction pattern, begin to move the eyepiece in the opposite direction.

Once you pass the focal point, you will again see expanding rings of light. Moreover, the picture should be completely similar to the previous one. The image of the star on both sides of the focus should look exactly the same - this is the main indicator of the quality of the optics. High-quality telescopes should produce a similar diffraction pattern on either side of the focus when the aperture is fully open.

LET'S START TESTING

It's time to start testing the optics. This is very easy to do: just open the lens completely by removing our cardboard with a hole. The main task is to compare the appearance of the diffraction pattern given by the telescope lens on both sides of the focus. At this stage it is no longer necessary to clearly see the Airy disk, so the telescope magnification can be reduced to 8-10 times the lens diameter in centimeters.

Point the telescope at one of the bright stars, bringing its image to the center of the field of view. Bring the image out of focus until 4-8 rings are visible. Do not overdo the defocusing, otherwise the sensitivity of the test will be lost. On the other hand, if the star is not sufficiently defocused, then it will be difficult to determine the reasons that generate images of poor quality. Therefore, at this moment it is important to find a “golden mean”.

If you see that the diffraction pattern on either side of the focus does not look the same, then it is very likely that the optics of the telescope you are testing suffer from spherical aberration. Spherical aberration occurs when a mirror or lens is unable to converge incoming parallel rays of light to a single point. As a result, the image never becomes sharp. The following case is possible: in front of the focus (closer to the telescope lens), the rays are concentrated along the edges of the disk, and behind the focus (further from the telescope lens) - towards the center. This leads to the fact that the diffraction pattern on different sides of the focus looks different. Spherical aberration is often found in reflectors whose main mirror is poorly parabolized.

Refractor lenses, in addition to spherical aberration, also suffer from chromatic aberration, when rays of different wavelengths converge at different points. In common two-lens achromats, the orange-red and bluish-green rays converge at a slightly different point than the yellow and dark red rays. Even further away from them is the focal point for the violet rays. Fortunately, the human eye is not very sensitive to dark red and violet rays. Although, if you have observed bright planets through a large refractor, you have probably noticed a violet halo generated by chromatic aberration surrounding images of bright planets in front of the focus.

When observing a white star, for example Spica, chromatic aberration will give the following picture: in front of the focus (when about three rings are visible), the disk acquires a greenish-yellow hue, possibly with a red border. When extending the eyepiece, as the rings begin to expand again after passing the focal point, a faint red dot will appear in the center of the picture. As you move the eyepiece further out, you will again see the greenish-yellow disk, but without the red border, and a blurry purple spot will appear in the center of the picture.

Please note another possible optical error. If the color does not appear evenly, but looks like an elongated stripe in the form of a small rainbow, this may be a signal that one of the lens components is poorly centered or tilted to the optical axis. However, be careful - a similar picture can be created by the atmosphere acting like a prism if you observe the star below 45° above the horizon.

To avoid the influence of color distortions on the test results, it is recommended to use a yellow filter. This is also useful when checking a reflector, the eyepiece of which can introduce color distortions.

DON'T BLAME THE TELESCOPE

The quality of a telescope's optics is not always the main culprit for poor images. Therefore, before sinning on optics, make sure that the influence of all other factors is absent or minimized.

Atmospheric turbulence. On a night with a turbulent atmosphere, the image of the star trembles and blurs, making any optical research impossible. It is best to postpone testing the telescope until the next time when observing conditions are more favorable.

When the atmosphere is turbulent, the diffraction rings take on jagged, jagged edges with wandering spiky projections.

Air flows inside the telescope tube. Slowly rising currents of warm air inside your telescope tube can create distortions that masquerade as optical defects. In this case, the diffraction pattern, as a rule, has an elongated sector on one side or, conversely, a flat sector. To eliminate the influence of air flows that usually appear when removing a tool from a warm room, you need to wait some time so that the air temperature inside the pipe becomes equal to the ambient temperature.

Updrafts of air inside a pipe are a common but temporary problem.

Eyepiece. To test a telescope by stars, you will need a high quality eyepiece, at least a symmetrical or orthoscopic system. If a telescope test shows poor results, and even more importantly, if someone else's telescope with your eyepiece shows the same results, then suspicion should fall on the eyepiece.

Gpaza. If you are farsighted or nearsighted, it is best to remove your glasses for the test. However, if your eyes have astigmatism, then you should leave the glasses.

Telescope adjustment. Telescopes whose optics are poorly aligned will perform poorly when tested. To eliminate this drawback, telescopes are equipped with special adjustment screws that allow all system components to be aligned to the same optical axis. Alignment methods are usually described in the instructions for the telescope (see also the following article “How to align the optics of a reflecting telescope”).

If you see the same asymmetry of the rings on both sides of the focus, this is a sure sign that the telescope optics need to be adjusted

Pinched optics. Optics that are not properly mounted in the frame can cause very unusual distortions in the diffraction pattern. Most of the reflectors I tested with the main mirror pinched gave diffraction patterns of a tri- or hexagonal shape. This drawback can be eliminated by slightly loosening the screws securing the mirror to the frame.

Most often, a similar picture can be observed in a reflecting telescope, the main mirror of which is strongly compressed in the frame.

OPTICAL DEFECTS

So, we come to the most important question: does the optics of this telescope have any defects and how severe are they? Errors in optical surfaces caused by various reasons, when mixed, affect the appearance of the diffraction pattern, which may differ from the illustrations given here, which show the “pure” effect of various optical defects. More often than not, however, the influence of one of the shortcomings significantly prevails over the others, making the test scores quite unambiguous.

Spherical aberration

Above we have already considered this type of distortion, caused by the inability of a mirror or lens to bring parallel incoming rays of light to one point. As a result of spherical aberration, a dark area forms in the center of the diffraction pattern on one side of the focus. However, there is one important note to make here: be careful not to confuse spherical aberration with a shadow from the secondary mirror. The fact is that in telescopes that have a lens darkened by a secondary mirror (reflectors, meniscus telescopes), when the star is defocused, an expanding dark area appears in the center of the light spot. But unlike spherical aberration, this dark spot appears equally both in front and behind the focus.

Zone errors

Zonal errors are small depressions or low tubercles located in the form of rings on the optical surface. Optical parts made on machine tools often suffer from this drawback. In some cases, zonal errors lead to a noticeable loss of image quality. To detect the presence of this defect, you should defocus the star image a little more than for other tests. The presence of one or more weak rings in the diffraction pattern on one side of the focus will indicate the presence of zonal errors.

“Gaps” in the diffraction pattern caused by zonal errors are best seen with a highly defocused image.

Edge blockage

A special case of a zonal error is an edge collapse. It is most often caused by excessive pressure on the mirror or lens during polishing. A collapsed edge is a serious defect in optics, since a large portion of the mirror or lens seems to be out of the game.

In reflectors, edge rollover reveals its presence during testing by blurring the edge of the central disk when the eyepiece is moved closer to the lens. On the other side of the focus, the diffraction pattern turns out to be undistorted, since the roll of the edge has almost no effect here. On the contrary, a refractor has a central disk that has blurred, jagged edges when the eyepiece is behind the focus. But in a refractor, the edges of the lenses are usually “hidden” in the mounts, so the rollover of the edges in telescopes of this type affects the image quality much less than in reflectors.

When the edge of the main mirror collapses, the contrast of the diffraction pattern in front of the focus drops sharply. The postfocal diffraction pattern remains virtually undistorted.

Astigmatism

This deficiency of optical systems manifests itself in the elongation of circular diffraction rings into ellipses, the orientation of which differs by 90° on opposite sides of the focus. Therefore, the easiest way to detect astigmatism in the system is to quickly move the eyepiece in and out, passing the focal point. Moreover, weak astigmatism is easier to notice when the star is only slightly out of focus.

Once you have confirmed that there are traces of astigmatism in the diffraction pattern, do a few more checks. Often astigmatism occurs due to poor alignment of the telescope. Additionally, many people have vision astigmatism without even realizing it. To check whether your eyes are causing astigmatism, try rotating your head to see if the orientation of the diffraction ellipses changes as you rotate your head. If the orientation changes, then the eyes are to blame. Also check whether astigmatism is caused by the eyepiece by rotating the eyepiece clockwise and counterclockwise. If the ellipses also begin to rotate, then the eyepiece is to blame.

Astigmatism can also be a symptom of improperly mounted optics. If you find astigmatism in the Newtonian system reflector, then try to slightly loosen the clamps of the main and diagonal mirrors in the frame. This is unlikely to be possible with refractors, so the presence of astigmatism in this type of telescope is the reason for filing claims against the manufacturer for incorrectly installing the lenses in the frame.

Astigmatism in Newtonian system reflectors can occur due to the fact that the surface of the diagonal mirror has deviations from the plane. This can be verified by turning the main mirror 45°. See if the orientation of the ellipses has changed by the same angle. If not, then the problem lies in a poorly made secondary mirror or poor alignment of the telescope.

The semimajor axes of ellipses caused by astigmatism rotate 90° as they pass through the focal plane.

Surface roughness

Another common problem with optical surfaces is a network of bumps or depressions (ripples) that appear after rough processing with a polishing machine. In the star test, this deficiency manifests itself in a sharp decrease in the contrast between the diffraction rings, as well as in the appearance of pointed protrusions. However, do not confuse them with diffraction by diagonal mirror extensions, the projections of which are located at equal angles (usually 60° or 90°). The type of diffraction pattern caused by the surface roughness of the optics is very similar to the diffraction pattern created by atmospheric disturbances. But there is one important difference - atmospheric distortions move all the time, then disappearing, then appearing again, but optical errors remain in place.

The type of diffraction pattern caused by the surface roughness of the optics is very similar to the pattern created by atmospheric disturbances. But there is one important difference - atmospheric distortions move all the time, disappearing and reappearing, while optical errors remain in place.

WHAT TO DO, IF…

Almost all telescopes detect more or less noticeable deviations from the ideal diffraction pattern during the star test. And it's not because they are all bad tools. It's just that this method is extremely sensitive to even the smallest optical errors. It is more sensitive than the Foucault or Ronchi test. So before you judge a tool, think about this.

Let's say the worst has already happened - your instrument does not pass the star test. Don't rush to get rid of this telescope right away. It is possible that you made a mistake about something. Although the optics testing techniques described here are fairly simple, they do require some experience. Try to consult with one of your more experienced comrades. Try to test someone else's telescope (again, don't rush into categorical statements if you think you've discovered some problems with your friend's telescope - not everyone may like such “good” news).

Finally, ask yourself, how good should my telescope be? Of course, we all want top-notch equipment, but can you really expect excellent images from an inexpensive spotting scope? I have met many amateur astronomers who took great pleasure in observing the sky with telescopes that had serious optical defects. Others could leave tools whose quality was approaching perfection for a long time to gather dust in the pantry. Therefore, here I would like to repeat one old truth: the best telescope is not the one that shows ideal optical characteristics, but the one that you use most often during observations.

Translation by S. Aksyonov

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If you decide to buy a telescope, then you first need to understand what it is, what types there are, and which option is better to choose. This is what we will try to help you figure out.

If you decide to buy a telescope, then you first need to understand what it is, what types there are, and which option is better to choose. This is what we will try to help you figure out.

What is a telescope and why is it needed?
A telescope is a device that allows you to observe various celestial objects that are very distant from the observation point. Most often they are used to observe celestial bodies, but sometimes terrestrial objects are also examined with their help. Previously, they were very expensive, and only astronomers and ufologists could afford them. Today, devices of this kind are much more affordable, and ordinary people can afford them. For example, the Astrologer store can help you buy them.

Optical telescopes
Different telescopes can operate in different ranges of the electromagnetic spectrum. The most common optical telescope. Almost all amateur telescopes today are optical. Such devices work with light. There are also radio telescopes, neutrino telescopes, gravitational telescopes, X-ray telescopes and gamma telescopes. However, all this applies to scientific equipment, which is not used in everyday life.

Types of telescopes
Optical telescopes, both professional and amateur, are divided into three types. The main criterion here is the telescope lens, or rather the principle by which it works. You can find various types of telescopes on the website www.astronom.ru.

Lens telescope
Lens refractors are called refractors, and they were the very first to be born. Their creator was Galileo Galilei. The advantage of such telescopes is that they require almost no special maintenance; they guarantee good color rendition and clear images. Such options are well suited for studying the Moon, planets, and double stars. It is worth noting that these devices are most suitable for professionals, since they are not so easy to use, and in addition they are quite large in size and high in cost.

Mirror telescope
Mirror reflectors are called reflectors. Their lenses consist only of their mirrors. Like a convex lens, a concave type mirror collects light at a specific point. If an eyepiece is placed at this point, the image can be seen. Among the advantages of such a telescope, the minimum price per unit of device diameter stands out, since large mirrors are much more profitable to produce than large lenses. They are also compact and easy to transport, while providing bright images with little distortion. Of course, DSLRs also have their drawbacks. This is additional time for thermal stabilization, lack of protection from dust and air, which can spoil the image.

Mirror-lens telescopes
They are called catadioptric and can use both lenses and mirrors. The advantage of such a telescope is its versatility, since with their help you can observe planets with the Moon, and deep space objects. They are also very compact and cost-effective. The only point is the complexity of the design, which complicates the independent adjustment of the device.