It's safe to say that everyone has dreamed of taking a closer look at the stars. You can use binoculars or a spotting scope to admire the bright night sky, but you are unlikely to be able to see anything in detail through these devices. Here you will need more serious equipment - a telescope. To have such a miracle of optical technology at home, you need to pay a large sum, which not all lovers of beauty can afford. But don't despair. You can make a telescope with your own hands, and for this, no matter how absurd it may sound, you don’t have to be a great astronomer and designer. If only there was a desire and an irresistible craving for the unknown.

Why should you try making a telescope?

We can definitely say that astronomy is a very complex science. And it requires a lot of effort from the person doing it. A situation may occur that you purchase an expensive telescope, and the science of the Universe will disappoint you, or you simply realize that this is not your thing at all.

In order to figure out what’s what, it’s enough to make a telescope for an amateur. Observing the sky through such a device will allow you to see many times more than through binoculars, and you will also be able to figure out whether this activity is interesting to you. If you are passionate about studying the night sky, then, of course, you cannot do without a professional apparatus.

What can you see with a homemade telescope?

Descriptions of how to make a telescope can be found in many textbooks and books. Such a device will allow you to clearly see the lunar craters. With it you can see Jupiter and even make out its four main satellites. The rings of Saturn, familiar to us from the pages of textbooks, can also be seen using a telescope made by ourselves. In addition, many more celestial bodies can be seen with your own eyes, for example, Venus, a large number of stars, clusters, nebulae.

A little about the telescope design

The main parts of our unit are its lens and eyepiece. With the help of the first part, the light emitted by celestial bodies is collected. How distant bodies can be seen, as well as the magnification of the device, depends on the diameter of the lens. The second member of the tandem, the eyepiece, is designed to enlarge the resulting image so that our eye can admire the beauty of the stars.

Now about the two most common types of optical devices - refractors and reflectors. The first type has a lens made of a lens system, and the second has a mirror lens. Lenses for a telescope, unlike a reflector mirror, can be found quite easily in specialized stores. Buying a mirror for a reflector will not be cheap, and making one yourself will be impossible for many. Therefore, as has already become clear, we will be assembling a refractor, and not a reflecting telescope. Let's finish the theoretical excursion with the concept of telescope magnification. It is equal to the ratio of the focal lengths of the lens and eyepiece.

How to make a telescope? We select materials

In order to start assembling the device, you need to stock up on a 1-diopter lens or its blank. By the way, such a lens will have a focal length of one meter. The diameter of the blanks will be about seventy millimeters. It should also be noted that it is better not to choose spectacle lenses for a telescope, since they generally have a concave-convex shape and are poorly suited for a telescope, although if you have them on hand, you can use them. It is recommended to use long-focal lenses with a biconvex shape.

As an eyepiece, you can take a regular magnifying glass with a thirty-millimeter diameter. If it is possible to get an eyepiece from the microscope, then it is certainly worth taking advantage of. It is also perfect for a telescope.

What should we make the housing for our future optical assistant from? Two pipes of different diameters made of cardboard or thick paper are perfect. One (the shorter one) will be inserted into the second, with a larger diameter and longer. A pipe with a smaller diameter should be made twenty centimeters long - this will ultimately be the eyepiece unit, and it is recommended to make the main one a meter long. If you don’t have the necessary blanks at hand, it doesn’t matter, the body can be made from an unnecessary roll of wallpaper. To do this, the wallpaper is wound in several layers to create the required thickness and rigidity and glued. How to make the diameter of the inner tube depends on what kind of lens we use.

Telescope stand

A very important point in creating your own telescope is preparing a special stand for it. Without it, it will be almost impossible to use it. There is an option to install the telescope on a camera tripod, which is equipped with a moving head, as well as fasteners that will allow you to fix different positions of the body.

Telescope assembly

The lens for the lens is fixed in a small tube with its convex outward. It is recommended to fasten it using a frame, which is a ring similar in diameter to the lens itself. Directly behind the lens, further along the pipe, it is necessary to equip a diaphragm in the form of a disk with a thirty-millimeter hole exactly in the middle. The purpose of the aperture is to eliminate image distortion caused by the use of a single lens. Also, installing it will affect the reduction of light that the lens receives. The telescope lens itself is mounted near the main tube.

Naturally, the eyepiece assembly cannot do without the eyepiece itself. First you need to prepare fastenings for it. They are made in the form of a cardboard cylinder and are similar in diameter to an eyepiece. The fastening is installed inside the pipe using two disks. They are the same diameter as the cylinder and have holes in the middle.

Setting up the device at home

The image must be focused using the distance from the lens to the eyepiece. To do this, the eyepiece assembly moves in the main tube. Since the pipes must be well pressed together, the required position will be securely fixed. It is convenient to perform the tuning process on large bright bodies, for example, the Moon; a neighboring house will also work. When assembling, it is very important to ensure that the lens and eyepiece are parallel and their centers are on the same straight line.

Another way to make a telescope with your own hands is to change the size of the aperture. By varying its diameter, you can achieve the optimal picture. Using optical lenses of 0.6 diopters, which have a focal length of approximately two meters, you can increase the aperture and make the zoom much closer on our telescope, but you should understand that the body will also increase.

Watch out - Sun!

By the standards of the Universe, our Sun is far from the brightest star. However, for us it is a very important source of life. Naturally, having a telescope at their disposal, many will want to take a closer look at it. But you need to know that this is very dangerous. After all, sunlight, passing through the optical systems we have built, can be focused to such an extent that it will be able to burn through even thick paper. What can we say about the delicate retina of our eyes?

Therefore, you need to remember a very important rule: you cannot look at the Sun through zooming devices, especially a home telescope, without special protective equipment. Such means are considered to be light filters and a method of projecting an image onto a screen.

What if you couldn’t assemble a telescope with your own hands, but you really want to look at the stars?

If suddenly, for some reason, assembling a homemade telescope is impossible, then do not despair. You can find a telescope in a store for a reasonable price. The question immediately arises: “Where are they sold?” Such equipment can be found in specialized astro-device stores. If there is nothing like this in your city, then you should visit a photographic equipment store or find another store that sells telescopes.

If you are lucky - there is a specialized store in your city, and even with professional consultants, then this is the place for you. Before going, it is recommended to look at an overview of telescopes. First, you will understand the characteristics of optical devices. Secondly, it will be more difficult to deceive you and slip you a low-quality product. Then you will definitely not be disappointed in your purchase.

A few words about buying a telescope through the World Wide Web. This type of shopping is becoming very popular nowadays, and it is possible that you will use it. It’s very convenient: you look for the device you need, and then order it. However, you may come across the following nuisance: after a long selection, it may turn out that the product is no longer in stock. A much more unpleasant problem is the delivery of goods. It is no secret that a telescope is a very fragile thing, so only fragments can be delivered to you.

It is possible to purchase a telescope by hand. This option will allow you to save a lot of money, but you should be well prepared so as not to buy a broken item. A good place to find a potential seller is astronomer forums.

Price per telescope

Let's look at some price categories:

About five thousand rubles. Such a device will correspond to the characteristics of a telescope made with your own hands at home.

Up to ten thousand rubles. This device will certainly be more suitable for high-quality observation of the night sky. The mechanical part of the body and equipment will be quite poor, and you may have to spend money on some spare parts: eyepieces, filters, etc.

From twenty to one hundred thousand rubles. This category includes professional and semi-professional telescopes. Surely a beginner will have no need for a mirror camera with an astronomical cost. This is simply, as they say, a waste of money.

Conclusion

As a result, we got acquainted with important information about how to make a simple telescope with your own hands, and some of the nuances of buying a new device for observing the stars. In addition to the method that we have considered, there are others, but this is a topic for another article. Whether you've built a telescope at home or purchased a new one, astronomy will take you into the unknown and provide experiences you've never experienced before.

Telescope- the dream of many, because there are so many stars in the universe that you want to look at each one. Store prices for this device are a little steep for ordinary people, so there is an option to make a telescope with your own hands.

How to make a telescope at home?

For the simplest telescope we need:

Lenses, 2 pcs.;
- thick paper, several sheets;
- glue;
- magnifying glass.

Telescope diagram.

There are two types of telescopes - refractors and reflectors. We will make a refracting telescope, since lenses for it can be bought at any pharmacy. A spectacle lens is required, diameter - 5 cm, diopters +0.5-1. For the eyepiece we will take a magnifying glass with a focal length of 2 cm.

Let's get started!

How to make the main tube for a telescope with your own hands?

From a sheet of thick paper, make a pipe with an approximate diameter of 5 cm. Then, straighten the sheet and paint the inside with black. You can use gouache paints. Rewind into a tube and secure the position using glue.

The length of our pipe should be about 2 meters.

How to make an eyepiece tube for a telescope?

We make this pipe in the same way as the main one. Length - 20 cm. Don't forget, this pipe will be put on the main one, so the diameter should be a little larger.

Once you glue the two pipes together, all that remains is to insert the lenses. Install them as shown in the diagram. Fix them well so that they are not damaged during use.

VIDEO. How to make a telescope?

Eyeglass lenses are a good material for a quality telescope. Before you buy a good telescope, you can make it yourself using inexpensive and affordable means. If you or your child want to get interested in astronomical observations, then building a homemade telescope will help you study both the theory of optical devices and the practice of observation.

Despite the fact that a refracting telescope built from spectacle glasses will not show you much in the sky, the experience and knowledge gained will be priceless. Afterwards, if you are interested in telescope construction, you can build a more advanced reflecting telescope, for example Newton’s system (see other sections of our website).

There are three types of optical telescopes: refractors (a lens system as a lens), reflectors (a lens - a mirror), and catadioptric (mirror-lens). All modern largest telescopes are reflectors, their advantage is the absence of chromatism and the possible large size of the lens, because the larger the diameter of the lens (its aperture), the higher its resolution, and the more light is collected, and therefore the fainter astronomical objects are visible through the telescope , the higher their contrast, and the greater the magnifications can be applied.

Refractors are used where high precision and contrast are required or in small telescopes. And now about the simplest refractor, with a magnification of up to 50 times, with which you can see: the largest craters and mountains of the Moon, Saturn with its rings (like a ball with a ring, not a “dumpling”!), bright satellites and the disk of Jupiter, some stars invisible to the naked eye.

Any telescope consists of a lens and an eyepiece; the lens builds a magnified image of the object that is viewed, then through the eyepiece. The distance between the lens and the eyepiece is equal to the sum of their focal lengths (F), and the magnification of the telescope is equal to Fob./Fok. In my case it is approximately 1000/23 = 43 times, i.e. 1.72D with an aperture of 25 mm.

1 - eyepiece; 2 - main pipe; 3 - focusing tube; 4 - diaphragm; 5 - tape that secures the lens to the third tube, which can be easily removed, for example, to replace the diaphragm; 6 - lens.

As a lens, let's take a blank lens for glasses (can be bought at any "Optics") with a power of 1 diopter, which corresponds to a focal length of 1 m. Eyepiece - I used the same achromatic coated gluing as for the microscope, I think for such a simple device - this is a good option. As a body, I used three tubes made of thick paper, the first about a meter, the second ~20 cm. The short one is inserted into the long one.

The lens - the lens is attached to the third tube with the convex side facing outwards, a disk is installed immediately behind it - a diaphragm with a hole in the center with a diameter of 25-30 mm - this is necessary, because a single lens, and even a meniscus, is a very bad lens and for obtaining of tolerable quality, you have to sacrifice its diameter. The eyepiece is in the first tube. Focusing is done by changing the distance between the lens and the eyepiece, moving or extending the second tube, it is convenient to focus on the Moon. The lens and eyepiece must be parallel to each other and their centers must be strictly on the same line; the diameter of the tube can be taken, for example, 10 mm larger than the diameter of the aperture hole. In general, when making a case, everyone is free to do as they wish.

A few notes:
- do not install another lens after the first one in the lens, as advised on some sites - this will only cause light loss and deterioration in quality;
- also do not install the diaphragm deep in the pipe - this is not necessary;
- it’s worth experimenting with the diameter of the diaphragm opening and choosing the optimal one;
- you can also take a lens of 0.5 diopters (focal length 2 m) - this will increase the aperture opening and increase the magnification, but the length of the tube will become 2 meters, which may be inconvenient.
A single lens is suitable for the lens, the focal length of which is F = 0.5-1 m (1-2 diopters). It's not difficult to get; it is sold in an optical store that sells glasses lenses. Such a lens has a whole bunch of aberrations: chromatism, spherical aberration. Their influence can be reduced by using lens aperture, that is, reducing the entrance aperture to 20 mm. What's the easiest way to do this? Cut a ring out of cardboard equal to the diameter of the pipe and cut the same entrance hole (20 mm) inside, and then place it in front of the lens almost close to the lens.

It is even possible to assemble a lens from two lenses in which the chromatic aberration that appears as a result of light dispersion will be partially corrected. To eliminate it, take 2 lenses of different shapes and materials - collecting and diverging - with different dispersion coefficients. A simple option: buy 2 spectacle lenses made of polycarbonate and glass. In a glass lens the dispersion coefficient will be 58-59, and in polycarbonate it will be 32-42. the ratio is approximately 2:3, then we take the focal lengths of the lenses with the same ratio, say +3 and -2 diopters. We add these values ​​and get a lens with a focal length of +1 diopter. We fold the lenses tightly; the collective should be the first to the lens. If it is a single lens, then it should have the convex side towards the object.

How to make a telescope without an eyepiece?! The eyepiece is the second important part of the telescope; we would be nowhere without it. It is made from a magnifying glass with a focal distance of 4 cm. Although for the eyepiece it is better to use 2 plano-convex lenses (Ramsden eyepiece), setting them at a distance of 0.7f. The ideal option is to get the eyepiece from ready-made instruments (microscope, binoculars). How to determine the magnification size of a telescope? Divide the focal length of the lens (for example, F=100cm) by the focal length of the eyepiece (for example, f=5cm), you get 20 times the magnification of the telescope.

Then we need 2 tubes. Insert the lens into one, and the eyepiece into the other; Then we insert the first tube into the second. Which tubes should I use? You can make them yourself. Take a sheet of whatman paper or wallpaper, but be sure to have a thick sheet. Roll the tube to fit the diameter of the lens. Then you fold another sheet of thick paper and place the eyepiece (!) tightly into it. Then insert these tubes tightly into one another. If a gap appears, wrap the inner tube in several layers of paper until the gap disappears.

Now your telescope is ready. How to make a telescope for astronomical observations? You simply blacken the inside of each pipe. Since we are making a telescope for the first time, we will use a simple method of blackening. Just paint the inside of the pipes with black paint.The effect of the first telescope created independently will be stunning. Surprise your family with your design skills!
Often the geometric center of the lens does not coincide with the optical one, so if you have the opportunity to have the lens sharpened by a specialist, do not neglect it. But in any case, an unground spectacle lens blank will do. The diameter of the lens is not of great importance for our telescope. Because spectacle lenses are highly susceptible to various obberations, especially the edges of the lens, then we will aperture the lens with a diaphragm of about 30 mm in diameter. But to observe different objects in the sky, the aperture diameter is selected empirically and can vary from 10 mm to 30 mm.

For an eyepiece, of course, it is better to use an eyepiece from a microscope, level or binoculars. But in this example I used a lens from a point-and-shoot camera. The focal length of my eyepiece is 2.5 cm. In general, any positive lens of small diameter (10-30mm) with a short focus (20-50mm) is suitable as an eyepiece.

Determining the focal length of the eyepiece yourself is easy. To do this, point the eyepiece at the Sun and place a flat screen behind it. We will zoom in and out of the screen until we get the smallest and brightest image of the Sun. The distance between the center of the eyepiece and the image is the focal length of the eyepiece.

Telescope made from spectacle glasses

What is needed to build a telescope from spectacle glasses. The simplest refracting telescope.

To build a telescope, you will need spectacle glass with a power of 1 diopter (focal length 1 m), which is a meniscus (convex-concave lens) with a diameter of 60 - 80 mm, and can be purchased in stores selling and making glasses. It is necessary to pay attention to the fact that the lens must have a positive optical power, i.e., be “converging”, in contrast to “scattering” glasses, which cannot build a real image of the object. Most of us know what a positive lens is, since we all used a magnifying glass for burning in childhood. In this case, the rays of the Sun are focused at a distance from the lens equal to the focal distance. The spectacle glass will serve as the telescope lens. Such a telescope is called a refractor from the word "refraction", i.e. "refraction". In the lens of a refracting telescope, light rays coming from the object of observation are refracted, as a result of which they are collected in the focal plane, where they are viewed by the observer through the eyepiece, i.e., through a magnifying glass of one design or another. In our case, the eyepiece can be a simple magnifying glass with a focal length of 20 - 70 mm, a camera lens, an eyepiece from binoculars, a spotting scope, a microscope, etc.

In addition to the lens and eyepiece, you will need several sheets of whatman paper, glue (PVA, carpentry, epoxy), a small amount of thick and thin cardboard. To make a tripod, you will need slats with a cross section of approximately 25x15 mm, 5 mm plywood, cuttings of an inch board, several small screws, three long and one short M6 bolts with wing nuts, glue.

If you cannot get a lens of 1 diopter, you can use another one, taking into account that the focal length of the lens will be equal to:

F (m) =1 m / optical power in diopters.

For example, for a 0.75 diopter lens:

F = 1 m / 0.75 = 1.33 m.

You just need to take into account that a telescope that is too long will be inconvenient to use, and a short-focus lens will produce an image of unsatisfactory quality. For these reasons, it is advisable to use spectacle glass with a focus of 0.6 - 1.5 m.

Helpful Hint: Eyeglass lenses usually have a dot mark near the center that indicates the optical center of the lens. It can differ significantly from the geometric center; this is taken into account when making glasses (when grinding glass). It is advisable to choose glass in which the optical center differs from the geometric one by a small amount.

Where to start? Frame, tube, eyepiece assembly.

It is best to start by making a lens frame (see drawing, item 1), the diameter of which, and, consequently, the diameter of the pipe, will depend on the size of the purchased spectacle glass. The frame will be a tube glued from whatman paper in several layers. The inner diameter of the frame should be equal to the diameter of our lens, and the length should be 70 - 80 mm. The lens is fixed with two paper or cardboard rings, which are tightly inserted inside the frame, clamping the glass on both sides. The frame must be sufficiently rigid.

Then it is necessary to glue together the main tube of the telescope (item 2) from several layers of whatman paper. This can be done by winding the sheets onto a ready-made frame and liberally coating the inner surface of the paper with glue. In this case, you need to make sure that the paper does not warp. The length of the tube should be slightly (150 - 200 mm) less than the focal length of the lens. The movable tube (item 3) is used for focusing, i.e., for aligning the focal planes of the lens and eyepiece. It should move easily "on friction", but not dangle. We glue it together from whatman paper in the same way as the main tube of our telescope.

The eyepiece frame, the design of which will depend on what we use for this purpose, can be inserted directly into the movable tube, but it is better, especially if the diameter of the eyepiece is small, to make a simple focusing unit. The basis of the assembly will be a ring of plywood (cut with a jigsaw and drill a hole) or two to three layers of thick cardboard. The unit operates “on friction”, and its design is clear from the drawing (item 4). The surface of the fixed tube of the eyepiece assembly can be covered with velvet or cloth to reduce friction, the movable one can be selected or machined from metal, or it can be glued together from several layers of not very thick, but dense, smooth paper. It needs to be given sufficient rigidity.

By moving the telescope's movable tube, the focal planes of the lens and eyepiece are roughly aligned (the same tube can be used with different lenses), and the eyepiece assembly allows for precise focusing.

Telescope test. Its main characteristics.

Now a few words about testing and setting up the telescope and its main characteristics. First of all, I’ll tell you about the magnification with which we will work. The magnification of a telescope is equal to the focal length of the objective divided by the focal length of the eyepiece. From this it is clear that by using different eyepieces, we can obtain different magnifications with the same lens. For example, for an eyepiece with a focal length of 50 mm (normal camera lens):

1000 mm / 50 mm = 20 times,

and for an eyepiece from a microscope with a focal length of 10 mm:

1000 mm / 10 mm = 100 times.

It may seem that by using long-focus glasses and short-focus eyepieces one can achieve very high magnification, however, after experimenting with a telescope made of spectacle glasses, we will very soon see that this is not the case. The imperfection of our lens imposes significant limitations. In practice, we will be able to use the constructed instrument with 20 - 50x magnification. This is enough to see much of what adorns the night sky but is inaccessible to the naked eye, such as bright nebulae, the ring of Saturn, the disk and moons of Jupiter, not to mention breathtaking panoramas of the Moon.

So, our telescope is ready, the glue has dried, the inner surfaces of the tube and frames are blackened with ink, and we can begin the first tests. Having aligned the focal planes of the lens and eyepiece, and resting the tube for stability on a window sill, window frame or other object, we will try to “focus” by moving the focusing tube with the eyepiece. Most likely, even with the best focusing, the image will be clouded with haze. This happens because only the central part of the spectacle glass produces an undistorted image. To build refractor telescopes with sufficiently large diameters, complex lenses are used in which these distortions, called aberrations, are corrected. It's okay, covering the edges of our lens with an opaque screen, we will achieve a good image. Such a screen is called a diaphragm (see devil, item 5). It makes sense to make several apertures according to the number of eyepieces, since at low magnifications the aberrations are less noticeable, and at higher magnifications they are more noticeable. The diaphragm is made in the form of a cardboard circle with a 10 - 30 mm hole in the middle, painted black and inserted into the lens frame in front of the spectacle glass. At magnifications of 10 - 20 times, you can use a 30mm aperture - this will allow you to see more faint objects (stars and nebulae); when observing the Moon with a magnification of 50 - 100 times, the effective lens aperture will have to be reduced to 15 - 10 mm. In all cases, the magnification and diameter of the aperture will need to be determined experimentally.

Here we come to another important parameter of the telescope - the diameter of the lens. This parameter is the main one and determines such characteristics as the penetrating force and resolution of the instrument. The first characteristic indicates the ability of the telescope to show faint objects and is expressed in stellar magnitudes. The second is the ability to separate closely spaced stars or features on the disks of planets and is expressed in angular quantities - in seconds and fractions of a second of arc. For example, we can say that the angular size of the visible disk of the Moon is about 30 minutes, and the human eye has a resolution of 1 - 2 minutes. Our telescope can have a resolution of about 10 arc seconds, i.e., at least 6 - 10 times higher than the naked eye. The penetrating power of the instrument is proportional to the square of the diameter of the lens, and if we take the pupil size of the human eye to be 7 mm, and the diameter of the telescope entrance aperture to be 20 mm, then our simplest refractor will allow us to observe stars and other bodies about 8 times fainter than with the naked eye . Those wishing to become more familiar with these and other concepts of geometric and physical optics, operating principles and features of various telescope systems are referred to the list of references at the end of this article.

Observations with a telescope.

Everyone probably knows that the most important instrument, the main tool of an astronomer, is the telescope. But what is the main advantage of a telescope over the naked eye? Not everyone knows this.

It is commonly believed that the main property of a telescope is to magnify images of celestial bodies. When approaching a telescope, schoolchildren usually ask: “How many times does it magnify?” In fact, the power of a telescope is determined not by the magnification it provides, but by the diameter of the lens. After all, the larger the diameter of the lens, the larger its area, and therefore the greater the amount of light that the lens collects. Even a school telescope with a lens diameter of only 80 mm collects about 250 times more light than the eye. This is understandable: the diameter of the pupil (5 mm) is 16 times smaller than the diameter of the school telescope, and 162 = 25. Therefore, through a school telescope we will see stars that are 250 times fainter than those visible to the naked eye. It must be remembered that stars, even in the most powerful telescope, appear to be luminous points, therefore the term “magnification” is not applicable to their observations.

Another thing is the Sun, Moon, planets, nebulae and other so-called extended celestial bodies. Thanks to the combination in the optical system of a telescope of a lens and a special complex magnifying glass - an eyepiece, it is possible to obtain enlarged images of these luminaries. Let's see how this happens.

A telescope lens is a system of lenses whose task is to construct a real image of the luminary. This image, obtained at the main focus of the lens, can be taken on the screen, photographed by placing a photographic plate here, or viewed through an eyepiece. The distance from the lens or eyepiece to the main focus is called the focal length. The eyepiece has its own focal length, usually many times smaller than the lens. The magnification of a telescope is equal to the ratio of the focal lengths of the lens and eyepiece.

It would seem that one should achieve the greatest possible magnification of the telescope in order to examine the smallest details on the Moon, Mars and other planets. In fact, the ability to examine certain small details (the resolving power of the telescope) is again determined not by magnification. and the diameter of the lens. To find out what the smallest details can be discerned in a given telescope, you need to divide 120 by the diameter of the lens, expressed in millimeters. We will obtain the apparent dimensions of the smallest discernible features in arcseconds. Let us recall that 1" arc is 1/3600°. This is the angle at which the thickness of an ordinary match is visible from a distance of 400 m. At the distance of the Moon, 1" arc corresponds to the linear size of the part of 2 km, at the distance of Mars (during the period of great opposition) - 300 km. Such details can be discerned in a telescope with a lens of 120 mm or more.

Of course, higher magnifications allow you to better see the fine details of the surface of the Moon or planets. But they also have negative sides. At high magnifications, the image becomes paler and less clear, as the amount of light collected by the lens is distributed over a larger area of ​​the image. In addition, at high magnifications, image jitter caused by atmospheric fluctuations increases, as well as distortions associated with imperfections in the telescope optics (aberrations). Therefore, it is better to choose not the highest magnification, but one at which the light can be seen most clearly through the telescope.

Telescopes come in various types. An amateur astronomer usually has to deal with two of them: a refractor and a reflector. A refractor - "refracting" - is the oldest type of telescope. Its lens consists of lenses that refract the rays falling on them.

In the USSR, two types of refracting telescopes are produced for schools. Large model (see picture) with an objective lens diameter of 80 mm, a focal length of 800 mm and three eyepieces giving magnification of 28, 40 and 80 times. The telescope is mounted on a so-called equatorial installation, which allows you to monitor the star for a long time, rotating the telescope around only one axis - the polar axis (directed towards the North Star). The inclination of the polar axis to the horizon must be equal to the geographic latitude of the place, which is determined from the map. The declination axis runs perpendicular to the polar axis. Rotating the tube around both axes, we point the telescope at the luminary, secure it with clamping screws and, watching the luminary through the eyepiece, slowly turn the telescope around the polar axis using a micrometer key.

Diagram of a homemade refracting telescope made from spectacle glasses:
1 - main tube, 2 - eyepiece tube, 3 - lens, A - lens frame, 5 - eyepiece, 6 - eyepiece frame, 7 - diaphragm.

A small model of a school refracting telescope (MSR) (see figure) has a lens with a diameter of 60 mm, a focal length of 600 mm. The eyepieces provide 30x and 60x magnification. Unlike the large model, the small one has an azimuthal installation. In it, the telescope tube can rotate around two axes: vertical and horizontal. To monitor the star, the telescope has to be rotated simultaneously around both axes, which is very inconvenient (how to avoid this is described in the “Handbook for an Amateur Astronomy” by P. G. Kulikovsky, “Science”, 1961, p. 246). After all, the daily path of a star across the sky is usually located at an angle to the horizon plane, and this angle changes during the day. Both telescopes come with various additional accessories: a solar screen, a zenith prism, dark glasses and light filters, etc. Often, an astronomy enthusiast does not have the opportunity to purchase a factory telescope. In this case, we can offer two options for a homemade telescope: for beginner amateurs - a refractor made from spectacle glasses, for more experienced ones - a reflector. Making a homemade refractor is accessible to any schoolchild.

First of all, you need to purchase a lens and eyepiece. For the lens, you can use a simple biconvex lens of 1 diopter (its focal length is 1 m). Such lenses are available in optical stores and pharmacies. Two lenses for glasses (“meniscus”) of +0.5 diopters each, located with their convex sides outward at a distance of 30 mm from one another, replace a lens of 1 diopter. Between them you need to place a diaphragm with a hole with a diameter of about 30 mm. Attachment lenses for a camera, for example, the “Amateur” type, are also suitable. A lens of 1 diopter can be replaced by lenses of 0.75 or 1.25 diopters (their focal lengths are 133 and 80 cm). The lens must certainly be round and have a large diameter (up to 50 mm). For the eyepiece, you can take a strong magnifying glass of small diameter, an eyepiece from a microscope (including a school type), from an old theodolite, level or binoculars.

To determine what magnification our telescope will give, we measure the focal length of the eyepiece. To do this, on a clear day, point the eyepiece at the Sun and place a sheet of white paper behind it. We will zoom in and out of the sheet until we get the smallest and brightest image of the Sun (to prevent the paper from catching fire, cover the eyepiece with an illuminated film or plate). The distance between the center of the eyepiece and the image is the focal length of the eyepiece. By dividing the focal length of the lens (it is equal to 100 cm divided by the number of diopters of the spectacle lens) by the focal length of the eyepiece, we obtain the magnification of the telescope.

Typically, you can get 20-50x magnification with a homemade refractor. The telescope tube can be made from paper. Take several sheets of large format paper and a round piece of wood with a diameter 2-3 mm larger than the objective lens. Wrap the blank with paper several times until the pipe is of sufficient strength and thickness. When winding the paper, coat each layer with glue - regular office glue, casein glue, or a paste made from potato or wholemeal wheat flour. Cover the outer surface of the pipe with light enamel or oil paint (you can use varnish), and black out the inside with ink to avoid harmful reflections of light from the walls of the pipe. It is better to do this before gluing the pipe. The pipe can also be made from sheet metal, duralumin and other materials. In the same way, a retractable tube of smaller diameter for the eyepiece is made. Its inner diameter depends on the outer diameter of the eyepiece frame. The main tube (1) is made ten centimeters shorter than the focal length of the lens; the length of the eyepiece tube (2) is about 40 cm. To bring the telescope to focus (“for clear vision”), the eyepiece tube must move in and out tightly, with friction. Stars in a telescope, when set to focus, appear as bright points rather than blurry disks. The objective lens (3) is inserted into the front end of the tube using a frame (4) consisting of two cardboard rings with a cut and two short paper tubes of slightly smaller diameter than the lens. Using these tubes, the lens is tightly clamped between the rings.

To make observation more convenient, you need to make a tripod for the telescope. The easiest way is to make a wooden azimuth tripod, on which the pipe rotates around two axes: vertical and horizontal. However, on such a tripod it is impossible to point the telescope at the sky near the zenith. This inconvenience can be eliminated. You just need to slightly change the design of the tripod. The pipe at the other end of the horizontal axis must be balanced with a load. To avoid having to support the pipe with your hand all the time, make a locking screw, or even better, two: for the vertical and horizontal axes.

With the help of the refractor you made, you will be able to observe the mountains on the Moon, the rings of Saturn, the phases of Venus, the disk of Jupiter and its 4 satellites, double stars, some star clusters - the Pleiades, the Manger. Observe sunspots by projecting an image of the Sun onto a screen - a sheet of white paper, protecting it from the direct rays of the Sun with a piece of cardboard with a hole in the middle, placed on a tube. For complex observations this tool is not sufficient.