Post about types of telescopes. The main characteristics of the telescope

In this section, we have 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.

The main characteristics of telescopes:

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

The telescope is more versatile optical instrument than a spotting scope. A wider range of multiplicity 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 objective (aperture). The bigger, the better. A large lens increases the aperture ratio of the telescope and allows you to view distant objects of low luminosity. But with an increase in the diameter of the lens, the dimensions of the telescope also increase, so it is important to understand in what conditions and for observing which objects you want to use it.

How to calculate the magnification (magnification) of a telescope?

Changing the magnification in the 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 resolution 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 more than 1.4 telescope diameters - 84).

Common Mistakes When Choosing a Telescope

The higher the multiplier, the better.
This is far from being the case 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 novice amateur astronomer, you should not chase after a large multiplicity. Observation of distant objects requires a high degree of training, knowledge and skills in astronomy. The moon and planets of the solar system can be observed at magnifications from 20x to 100x.
Buying a reflector or a large refractor for observations from a balcony or city apartment window
Reflectors (mirror telescopes) are very sensitive to atmospheric fluctuations and 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 tube length will exceed 1 meter), so it is not possible to use them in city apartments.
Buying a telescope on an equatorial mount as a first
The equatorial mount is quite difficult to master and requires some training and skill. If you are a novice astronomer, we would recommend purchasing a telescope with an azimuth or 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 of budget optical glass will adversely affect image quality. Conversely, installing a professional eyepiece on an inexpensive device will not lead to the desired result.

Frequently asked Questions

I want a telescope. Which one should I buy?
A telescope is not a thing that can be bought 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 reaches the Earth for years). 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 a child. Which one to buy?
Especially for children, many manufacturers have introduced children's telescopes into their range. This is not a toy, but a full-fledged telescope, usually a long-focus refractor-achromat on an azimuth mount: it is easy to install and set up, it will show the Moon and planets well. Such telescopes are not too powerful, but they are inexpensive, and you will always have time to buy a more serious telescope for a child. Unless, of course, the child is interested in astronomy.
I want to look at the moon.
You will need a telescope "for near space". According to the optical scheme, long-focus refractors are best suited, as well as long-focus reflectors and mirror-lens telescopes. Choose a telescope of these types to your taste, focusing on the price and other parameters you need. By the way, with such telescopes it will be possible to look at not only the Moon, but also the planets of the solar system.
I want to look at distant space: nebulae, stars.
For these purposes, any refractors, short-focus reflectors and mirror-lens telescopes are suitable. Choose 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 mirror-lens telescopes. They are good for ground-based observations, and for the solar system, and for deep space. Many of these telescopes have a simpler mount, have computer aiming, and are a great option for beginners. But such telescopes are more expensive than lens or mirror models. If the price is of decisive importance, you can look at the long-focus refractor. For beginners, it is better to choose an azimuth mount: it is easier to use.
What is a refractor and reflector? Which is better?
Telescopes of various optical schemes will help to visually approach the stars, which are similar in results, but the mechanisms of the device are different and, accordingly, the features of the application are different.
A refractor is a telescope that uses optical glass lenses. Refractors are cheaper, they have a closed pipe (neither dust nor moisture will get into it). But the tube of such a telescope is longer: these are the features of the structure.
The reflector uses a mirror. Such telescopes are more expensive, but they have smaller dimensions (shorter tube). However, the mirror of the telescope may dim over time and the telescope will become "blind".
Any telescope has its pros and cons, but for any task and budget, you can find the perfect 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 more faint objects can be seen and more detail can be seen. 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. Long focal length starts at 8 units, such a telescope will increase more, but the viewing angle will be smaller.
This means that a large magnification is needed to observe the Moon and planets. Aperture (as an important parameter for the amount of light) is important, but these objects are already bright enough. But for galaxies and nebulae, the amount of light and aperture are just more important.
What is the magnification of a telescope?
Telescopes visually magnify an object so much that you can see details on it. The multiplicity will show how much you can visually enlarge something that the observer's gaze is directed at.
The magnification of a telescope is largely limited by its aperture, that is, by the limits 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). Several eyepieces are usually attached to one telescope, and the magnification factor can thus be changed.
What can I see with a telescope?
It depends on the characteristics of the telescope, 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 furrows 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, Mars clouds, star galaxies and nearest 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 the telescope. In fact, it increases the magnification of the telescope several times, increasing the focal length of the lens.
The Barlow lens does work, but its possibilities 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 best?
Telescope mount - the base on which the pipe is fixed. The mount supports the telescope, and its specially designed mount allows you not to fix the telescope rigidly, but also to move it along various trajectories. This is useful, for example, if you need to follow the movement of a celestial body.
The mount is just as important for observations as the main body 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 (easier and easier to set up, but hard to keep a star in view), equatorial (harder to set up, heavier), Dobsonian (a kind of azimuth for floor mounting), GoTo (self-guided telescope mount, you only need to enter a target ).
We do not recommend an equatorial mount for beginners: it is difficult to set up and use. Azimuth for beginners - that's it.
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.
Telescopes Maksutov-Cassegrain due to the design do not have side glare and their focal length is longer. Such models are considered to be more preferable for the study of planets (although this statement is practically disputed). But they will need a little more time for thermal stabilization (starting 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, they will weigh a little less. But they have side glare, shorter focal length, and less contrast.
Why are filters needed?
Filters will be needed for those who want to take a closer look at the object of study and better consider it. As a rule, these are people who have already decided on a goal: near space or far space.
Distinguish between planetary and deep space filters that are optimally suited for studying the target. Planetary filters (for the planets of the solar system) are optimally matched 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, in order to view the earth satellite in all details 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 loss of vision.
Which manufacturer is the best?
From what is presented in our store, we recommend paying attention to Celestron, Levenhuk, Sky-Watcher. There are simple models for beginners, separate additional accessories.
What can you buy with a telescope?
There are options, and they depend on the wishes of the owner.
Filters for planets or deep space - for better results and image quality.
Adapters for astrophotography - for documenting what has been seen through a telescope.
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 schemes of modern eyepieces differ, respectively, the eyepieces themselves are different in price, viewing angle, weight, quality, and most importantly, the focal length (and the final magnification of the telescope depends on it).
Of course, before such purchases, it is worth clarifying whether the add-on is suitable for the telescope.
Where should you look with a telescope?
Ideally, to work with a telescope, you need a place with a minimum of illumination (urban illumination by lanterns, illuminated advertising, the light of residential buildings). If there is no known safe place outside the city, you can find a place within the city, but in a rather dimly lit place. Clear weather is required for any sightings. Deep space is recommended to be observed 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 something further than the moon.

Main criteria for choosing a telescope

Optical design. Telescopes are mirror (reflectors), lens (refractors) and mirror-lens.
Lens diameter (aperture). The larger the diameter, the greater the luminosity of the telescope and its resolving power. The more distant and dim objects can be seen in it. On the other hand, the diameter greatly affects the dimensions and weight of the telescope (especially the lens one). It is important to remember that the maximum useful magnification of a telescope cannot physically exceed 1.4 of its diameter. Those. with a diameter of 70 mm, the maximum useful magnification of such a telescope will be ~98x.
Focal length is how far the telescope can focus. Long focal length (long focal length telescopes) means higher magnification but smaller field of view and aperture ratio. Suitable for detailed viewing of small distant objects. Short focal length (short focus telescopes) means low magnification but large field of view. Suitable for observing extended objects such as galaxies and for astrophotography.
mount is a method of attaching a telescope to a tripod. Azimuthal (AZ) - freely rotates in two planes like a photo tripod. Equatorial (EQ) is a more complex mount that adjusts to the celestial pole and allows you to find celestial objects, knowing their hour angle. The Dobson mount (Dob) is a variation of the azimuthal mount, but more suitable for astroobservations and allows you to install larger telescopes on it. Automated - computerized mount for automatic targeting of celestial objects, uses GPS.

Pros and cons of optical circuits

Long-focus refractors-achromats (lens optical system)

Short-focus refractors-achromats (lens optical system)

Long focus reflectors (mirror optical system)

Short focus reflectors (mirror optical system)

Mirror-lens optical system (catadioptric)

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

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

What can be seen with a telescope?

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

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

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

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

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

An attribute of the childhood of many generations of our fellow citizens is an inquisitive astronomer with the same pointed hat and telescope. Someone grew up, and someone still remained a romantic, fond of endless space and stars, in search of planets inhabited by brothers in mind. For such professionals, many models of these devices are produced annually, the types of which we will consider in the article.

So, their main types are:

lens (known since the time of Galileo, refractors);
mirror (they are also reflectors);
catadioptric, which are combined mirror-lens devices.

We will assume that before you buy a telescope, you have already chosen a list of objects for study that you are interested in. Therefore, in the following, we will focus on designs and technical characteristics, leaving aside the question of their applicability.

The lens "eyes of astronomers" are made on the basis of biconvex lenses that collect reflection from the observed objects at a certain focus. The lens refracts light in a certain way, therefore, because of this property, such a device is also known as a refractor. Its history is rich in the names of designers. Known refractor:

Galileo (biconvex lens - objective and biconcave - eyepiece);
Kepler;
achromatic (the most optically perfect).

Its advantages are the simplicity and reliability of the design, excellent contrast and thermal stabilization, unloaded adjustments, the ability to observe any astronomical objects. The disadvantages include the high specific cost of an inch of aperture compared to other types of models, high weight and size indicators, the inability to observe relatively distant objects of the solar system.

In reflectors, instead of lenses, concave, convex mirrors are used, which allow using a lens eyepiece at the focal point to see an image that is clean from chromatic and spherical aberrations. Newton, Gregory, Cassegrain, Ritchie-Chretien had a hand in the idea of developing and manufacturing this type of telescope ... As a result, the model created by Isaac Newton is better known to contemporaries in practice.

It is worth buying a mirror telescope because of:

more than competitive cost in comparison with catadioptrics and refractors;
relatively small weight and size indicators;
the possibility of observing distant nebulous astronomical objects;
high image quality (without certain noise, good brightness, etc.)

Purchasing barriers may include:

loss of contrast due to mirror configuration;
slow thermal stabilization;
exposed to direct exposure to air, dust, moisture open design;
the constant need for adjustment or collimation, especially after moving the device to another place.

catadioptric- optical devices that incorporate the best features of refractors and reflectors. The greatest demand on the market is for such telescopes built according to several schemes. Their names are given in accordance with the names of the inventors - Schmidt-Cassegrain and Maksutov-Cassegrain. Both options are thought out to the maximum, they implement all sorts of methods of protection against optical distortions, the influence of third-party factors - humidity, temperature ...

You can buy a catadioptric telescope, taking into account its following positive features:

excellent versatility in applicability;
better aberration correction;
minimizing the influence of third-party factors on the image;
lower cost of large apertures compared to competitors.

The disadvantages include:

long process of thermal stabilization;
practical impossibility of self-adjustment;
high cost in the segment of equipment of medium and low "vigilance", i.e. observation of nearby objects.

The sky beckons us when we look at its open spaces. What is hidden behind the clouds, and what is in its impenetrable darkness? Of course, we were able to get some idea of these questions with the help of a telescope. Undoubtedly, this is a unique device that gave us a magnificent picture of space. And undoubtedly, it brought our understanding of the heavenly space closer.

It is known that the first telescope was created by Galileo Galilei. Although few people know that he used the early discoveries of other scientists. For example, the invention of the telescope for navigation.
In addition, glass craftsmen have already created glasses. In addition, lenses were used. And the effect of refraction and magnification of glass has been more or less studied.

Galileo's first telescope

Of course, Galileo achieved a significant result in the study of this area. In addition, he collected and improved all the developments. And as a result, he developed and introduced the world's first telescope. In truth, it only had a threefold increase. But it was distinguished by high image quality at that time.

By the way, it was Galileo who called his developed object a telescope.
In the future, the scientist did not stop there. He improved the device up to twenty times the image magnification.
It is important that Galileo not only developed the telescope. Moreover, he was the first to use it for space exploration. In addition, he made a lot of astronomical discoveries.

Telescope characteristics

The telescope consists of a tube that stands on a special mount. It is equipped with axes for aiming at the observed object.
In addition, the optical device has an eyepiece and a lens. Moreover, the rear plane of the lens is perpendicular to the optical axis, and is connected to the front surface of the eyepiece. Which, by the way, is similar to the objective in relation to the optical axis.

It is worth noting that a special device is used for focusing.
The main characteristics of telescopes are magnification and resolution.
Image magnification depends on the focal length of the eyepiece and the object.
Resolution is related to the refraction of light. Thus, the size of the observed object is limited by the resolution of the telescope.

Types of telescopes in astronomy

The varieties of telescopes are associated with different construction methods. More precisely, the use of various tools as a lens. In addition, it matters for what purpose the device is needed.
Today, there are several main types of telescopes in astronomy. Depending on the light-harvesting component, they are lens, mirror and combined.

Lens telescopes (diopter)

In other words, they are called refractors. These are the very first telescopes. In them, light is collected by a lens, which is bounded by a sphere on both sides. Therefore, it is considered biconvex. In addition, the lens is a lens.
Interestingly, you can use not just a lens, but a whole system of them.

It is worth noting that convex lenses refract light rays and bring them into focus. And in it, in turn, an image is built. An eyepiece is used to view it.
What is important, the lens is set so that the focus and the eyepiece coincide.
By the way, Galileo invented the refractor. But modern devices consist of two lenses. One of them collects light, and the other scatters. That allows to reduce deviations and errors.

Mirror telescopes (cataptric)

They are also called reflectors. Unlike the lens type, their lens is a concave mirror. It collects starlight at one point and reflects it to the eyepiece. In this case, the errors are minimal, and the decomposition of light into rays is completely absent. But the use of a reflector limits the field of view of the observer.
Interestingly, mirror telescopes are the most common in the world. Because their development is much easier than, for example, lens devices.

Catadioptric telescopes (combined)

These are mirror lenses. They use both lenses and mirrors to produce images.

In turn, they were divided into two subspecies:
1) Schmidt-Cassegrain telescopes - they have a diaphragm installed in the very center of the curvature of the mirror. This eliminates spherical disturbances and deviations. But the field of view and image quality increase.
2) Maksutov-Cassegrain telescopes - a plano-convex lens is installed in the region of the focal plane. As a result, field curvature and spherical deflection are prevented.

It should be noted that in modern astronomy, it is the combined type of instruments that is most often used. By mixing two different elements to collect light, they produce better data.

Such devices are capable of receiving only one wave of signals. Antennas transmit signals and process them into images.
Radio telescopes are used by astronomers for scientific research.

Infrared telescope models

They are very similar in design to optical mirror telescopes. The principle of obtaining an image is almost the same. The rays are reflected by the lens and are collected at one point. Next, a special device measures the heat and photographs the result.

Modern telescopes

A telescope is an optical instrument for observation. It was invented almost half a century ago. During this time, scientists changed and improved the device. Indeed, many new models have been created. Unlike the first ones, they have an increased quality and an increase in the image.

In our age of technology, computer telescopes are used. Accordingly, they are equipped with special programs. What is important, the modern prototype takes into account that each person's perception of the eyes is different. For high accuracy, the image is transmitted to the monitor. Thus, the image is perceived as it really is. In addition, this method of observation eliminates any distortion.

In addition, scientists of our generation use not one device at the same time, but several. Moreover, unique cameras are connected to the telescope, which transmit information to a computer. This allows you to get clear and accurate information. Which, of course, are used to study and.

Interestingly, now telescopes are not just instruments for observation. But also devices for measuring distances between space objects. For this function, spectrographs are connected to them. And the interaction of these devices provides specific data.

Other classification

There are also other types of telescopes. But they are used for their own purpose. For example, X-ray and gamma-ray telescopes. Or ultraviolet devices that filter the picture without processing and exposure.
In addition, devices can be divided into professional and amateur. The former are used by scientists and astronomers. Obviously, the latter are suitable for home use.

How to choose a telescope for astronomy lovers

Choosing a telescope for astronomy enthusiasts is based on what you want to observe. In principle, the types and characteristics of devices are described above. You just need to choose which one you like best. It is better, in my opinion, to dwell on a lens or a combined form. But the choice, of course, is yours.

According to the Internet, the best amateur telescopes are represented by companies: Celestron, Bresser and Veber.

The telescope has been studying the life of planets for hundreds of years

The creation and development of the telescope, in fact, made it possible to make a huge step in space exploration. Probably everything we know was formed with the help of this device. Although, of course, one should not underestimate the very activities of scientists.
Today we looked at some types of telescopes and their characteristics. Definitely, the progress of technology is visible. And as a result, we learned a lot of interesting things about space objects and space itself. In addition, we can admire the beautiful sky and get to know it thanks to this wonderful invention.

Visually m t \u003d 2 m, 1 + 5 lgD, depends on the diameter D of the lens.

photographic plate m = 5 lgD + klgt – 1 m

t– duration of exposure;

k – 2, 1 – 3, 1 depends on the sensitivity of the photographic plate.

For reflector m before = 2,5 lg

D is the diameter of the objective mirror;

β is the diameter of the star image;

t - exposure time;

k is the quantum yield, equal to the ratio of registered photons to the number of photons that arrived at the receiver;

S is the brightness of the night sky background.

Resolution- the minimum angular distance of two objects at the limit of visibility.rad = 206 265 ʺ

Atmosphere reduces resolution .

In visual observations, the eye is most sensitive to radiation with λ 5500 Ǻ. φ = .

Disadvantages and advantages of reflectors and refractors

lenses and concave mirrors have errors - aberrations.

the lens has chromatic aberration, which is difficult to reduce, mirrors do not have such aberration.

large diameter lenses are more difficult to manufacture than a mirror.

Photographs of telescopes

Figure 40. Telescope - refractor of the Pulkovo Observatory.

Figure 41. The world's largest 6-meter telescope -

reflector

meniscus telescope

This is a mirror-lens telescope. In it, the shortcomings of a spherical mirror are corrected by a thin convex-concave lens of small curvature. This lens is called meniscus.

The path of rays in optical telescopes.

Figure 42. Schemes of the path of rays in telescopes: a) refractor;

b) reflector; c) meniscus telescope.

Telescopes: radio, infrared, x-ray and gamma electromagnetic waves. neutrino telescopes.

radio telescopes.

Main parts: antenna; sensitive radio receiver with amplifier.

The power of cosmic radio emission is very small. A special unit of measurement "Yang" was introduced for it - in honor of the American engineer K. Jansky, who first discovered cosmic radio emission in 1932.

1 Jan = 10 -26

In these units, the spectral flux density is measured, in the radio range, i.e. the amount of energy in a single frequency interval incident on a single area (1m 2), perpendicular to it, in 1 second.

Figure 43. Antenna of the 300-meter radio telescope in Arecibo, located in a bowl-shaped valley

Figure 44. Radio telescope them. Allen

Figure 45. Radio telescope RATAN 600 ( general form and antenna fragment)

All optical can be divided according to the type of the main light-collecting element into lens, mirror and combined - mirror-lens. All systems have their advantages and disadvantages, and when choosing an appropriate system, several factors must be taken into account - the objectives of observations, conditions, requirements for transportability and weight, the 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. 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 at a certain point - focus. Therefore, lens telescopes are often called refractors(from lat. refract- refract).

AT refractor Galileo(created in 1609) two lenses were used to collect as much starlight as possible and allow the human eye to see it. The first lens (lens) is convex, it collects light and focuses it at a certain distance, and the second lens (playing the role of the eyepiece) is concave, it turns the converging beam of light rays back into a parallel one. Galileo's system produces a straight, upside-down image, but suffers greatly from chromatic aberration that spoils the image. Chromatic aberration appears as false coloring 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 not essential 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 the 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 built by the lens mounted on a special tripod).

These difficulties of refractors at one time even the great Newton led to the conclusion that it was impossible to correct the chromatism of refractors. But in the first half of the XVIII century. appeared achromatic refractor.

Among amateur instruments, two-lens achromatic refractors are the most common, but more complex lens systems also exist. Typically, an achromatic refractor lens consists of two lenses of different types of glass, with one converging and the other diverging, and this can significantly reduce spherical and chromatic aberration (image distortion 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 effect of chromatic aberration on the image is reduced to an almost imperceptible value. True, this is achieved through the use of special types of glasses, which are expensive to manufacture and process, and 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, giving ease of use and reliability;

practically no special maintenance is required;

fast thermal stabilization;

excellent for observations of the moon, planets, double stars, especially at large apertures;

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

good color reproduction in achromatic performance and excellent in apochromatic;

the closed pipe excludes the air currents spoiling the image, and protects optics from dust and pollution;

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 in comparison with reflectors or catadioptrics of the same aperture;

price and bulkiness limit the largest practical aperture diameter;

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

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

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

We recommend the Levenhuk Astro A101 60x700 refractor telescope to anyone who wants to learn the basics of astronomy and observations of stars and planets. Also, this telescope will satisfy the higher demands of an experienced observer, since this model gives a very high image quality.

For many people who are passionate about astronomy, it is extremely important to use every free minute for interesting research. However, unfortunately, there is not always 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 refractor telescope
Levenhuk Skyline 80x400 AZ Your ideas about astronomical observations will change: now you can carry your telescope with you in a car, on an airplane, on a train, that is, wherever you go, you can devote time to your hobby everywhere.

The Orion GoScope 70 refractor telescope is a portable achromat that will allow you to study distant celestial bodies with high definition. In fact, this telescope is already fully assembled and ready to go, and placed in a special convenient backpack. You only need to 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 able to collect light at some point. If you place an eyepiece at this point, you can see the image.

One of the first reflectors was a reflecting telescope Gregory(1663), who invented a telescope with a parabolic main mirror. The image that can be observed in 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 fixed in front of the main one and is output to the observer through a hole in the center of the main mirror.

Disappointed in contemporary refractors, I. newton in 1667 he began the development of a reflecting telescope. Newton used a metal primary mirror (glass mirrors coated with silver or aluminum came later) to collect light, and a small flat mirror to deflect the collected light beam at a right angle and output it to the side of the tube into the eyepiece. Thus, we managed to cope with chromatic aberration - instead of lenses, this telescope uses mirrors that equally reflect light from different lengths waves. 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, which is why a Newtonian reflector with a spherical mirror is one of the most affordable types of telescopes, including those for self-production.

Scheme proposed in 1672 by Loren Cassegrain, outwardly 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 less central shielding. The traditional Cassegrain reflector is not technologically advanced in mass production (complex mirror surfaces - parabola, hyperbola), and also has an undercorrected coma aberration, but its modifications remain popular in our time. In particular, in a telescope Richie-Chrétien hyperbolic primary and secondary mirrors are used, which makes it possible to develop large fields of view, free from distortions, and, which is especially valuable, for astrophotography (the famous Hubble orbital telescope was designed according to this scheme). In addition, on the basis of the Cassegrain reflector, popular and technological catadioptric systems were later developed - Schmidt-Cassegrain and Maksutov-Cassegrain.

In our time, a reflector is most often called a telescope made according to Newton's scheme.. Having a small spherical aberration and complete absence chromatism, it is, however, not completely free from aberrations. Not far from the axis, coma (non-isoplanatism) begins to appear - an aberration associated with the uneven increase in different annular aperture zones. Coma leads to the fact that the image of the star looks not like a circle, but like a projection of a cone - a sharp and bright part towards the center of the field of view, a dull and rounded part away from the center. The 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" (aperture-fast) Newtons at the edge of the field of view. To correct coma, special lens correctors are used, which are installed in front of the eyepiece or camera.

As the most affordable do-it-yourself reflector, the Newton is often made on a simple, compact and practical Dobsonian mount and as such is the most portable telescope given the available aperture. Moreover, not only amateurs, but also commercial manufacturers are engaged in the production of "dobsons", and telescopes can have apertures of up to half a meter or more.

Advantages of reflectors:

the lowest cost per unit of aperture diameter in comparison with refractors and catadioptrics - large mirrors are easier to manufacture than large lenses;

relatively compact and transportable (especially in the Dobson 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 little 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;

an open pipe is not protected from dust and thermal currents of air 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 rich experience in such research? In both cases, your reliable assistant will be the Bresser Venus 76/700 Newtonian reflector - 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 nebula in Orion.

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

If you are attracted by the unknown objects located in the depths of outer space, then you, no 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 a great telescope for amateur astronomers who need 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 of the large objects from the NGC and Messier catalog.

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 higher aperture of the 130ST EQ will make deep-sky objects more accessible. Also, the telescope has a shorter tube - only 61cm, while the model 130 EQ has a 83cm tube.

Catadioptric (mirror-lens) telescopes

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

in telescopes Schmidt-Cassegrain (Sh-K) the primary and secondary mirrors are spherical. Spherical aberration is corrected by a full-aperture Schmidt correction plate at the tube inlet. This plate appears flat from the side, but has a complex surface, the manufacture of which is the main difficulty in the manufacture of the system. However, the American companies Meade and Celestron have successfully mastered the production Sh-K systems. Among the residual aberrations of this system, field curvature and coma are the most noticeable, 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. At the same time, there are no stretch marks for attaching the secondary mirror, and a 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, it has spherical mirrors, and a full-aperture lens corrector - a meniscus (convex-concave lens) is engaged in correcting aberrations. Therefore, such telescopes are also called meniscus reflectors. Closed pipe and no stretch marks - also advantages of M-K. Almost all aberrations can be corrected by selecting the system parameters. The exception is the so-called higher-order spherical aberration, 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 block, mechanically fixed on the meniscus, or as an aluminized central section of the back surface of the meniscus. In the first case, a better correction of aberrations is provided, 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 quality of manufacture, the M-K system is able to give a slightly better image than the S-K with similar parameters. But big M-K telescopes require more time for thermal stabilization, tk. a thick meniscus cools much longer than the Schmidt plate, and for M-K, the requirements for the rigidity of the corrector mounting increase, and the entire telescope turns out to be heavier. Therefore, the application for small and medium apertures of the M-K system is traced, and for medium and large apertures - Sh-K.

There are also Schmidt-Newton catadioptric systems and Maksutov-Newton having character traits 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 (the Klevtsov system, "spherical cassegrains," etc.).

Advantages of catadioptric telescopes:

high level of aberration correction;

universality - well suited for observations of planets and the moon, and for objects of deep space;

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

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

larger apertures are significantly cheaper than comparable refractors.

Disadvantages of catadioptric telescopes:

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

greater cost than reflectors of equal aperture;

the complexity of the design, which makes it difficult to independently adjust the tool.

Levenhuk SkyMatic 105 GT MAK is an excellent auto-guided telescope, small in size and weight, but with high resolution and high quality image. 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 able to show compact globular clusters and planetary nebulae.

Every astronomer, whether a novice or a more experienced amateur, knows what excitement 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 is seriously spoiled, in particular, if the telescope is "caught" heavy and bulky. The lion's share of time in this case is taken up by carrying, assembling and setting up. 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 valuable observing time on anything else.

Vixen VMC110L telescope on Sphinx SXD mount - 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 mount with computer guidance Sphinx SXD. In addition to a real computer planetarium in a control panel with a large color screen, it has a periodic error correction function, a polar finder is the main thing that is necessary for the most accurate pointing of the telescope at the photographed object.