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Do-it-yourself spyglass at home. Newtonian telescope from what is at hand

Do you suddenly want to make a telescope with your own hands? Nothing strange. Yes, nowadays it is not difficult to buy almost any optical device, and not so expensive. But sometimes a person is attacked by a thirst for creativity: he wants to figure out what laws of nature the principle of operation of a device is based on, he wants to design such a device from start to finish and experience the joy of creativity.

DIY spyglass

So, you get down to business. First of all, you will learn that the simplest telescope consists of two biconvex lenses - the objective and the eyepiece, and that the magnification of the telescope is obtained by the formula K = F / f (the ratio of the focal lengths of the lens (F) and the eyepiece (f)).

Armed with this knowledge, you go digging through boxes of various junk, in the attic, garage, shed, etc. with a clearly defined goal - to find more different lenses. These can be glasses from glasses (preferably round ones), watch magnifiers, lenses from old cameras, etc. Having collected a supply of lenses, start measuring. You need to choose a lens with a larger focal length F and an eyepiece with a smaller focal length f.

Measuring focal length is very simple. The lens is directed at some light source (a light bulb in the room, a lantern on the street, the sun in the sky or just a lit window), a white screen is placed behind the lens (a sheet of paper is possible, but cardboard is better) and moves relative to the lens until It will not produce a sharp image of the observed light source (inverted and reduced).

After this, all that remains is to measure the distance from the lens to the screen with a ruler. This is the focal length. You are unlikely to cope with the described measurement procedure alone - you will need a third hand. You'll have to call an assistant for help.

Once you have selected your lens and eyepiece, you begin constructing the optical system to magnify the image. You take the lens in one hand, the eyepiece in the other, and through both lenses you look at some distant object (not the sun - you can easily be left without an eye!). By mutually moving the lens and eyepiece (trying to keep their axes on the same line), you achieve a clear image.

The resulting image will be enlarged, but still upside down. What you are now holding in your hands, trying to maintain the achieved relative position of the lenses, is the desired optical system. All that remains is to fix this system, for example, by placing it inside a pipe. This will be the spyglass.

But don't rush into assembly. Having made a telescope, you will not be satisfied with the image “upside down”. This problem is solved simply by a wrapping system obtained by adding one or two lenses identical to the eyepiece.

You can obtain a wraparound system with one coaxial additional lens by placing it at a distance of approximately 2f from the eyepiece (the distance is determined by selection).

It is interesting to note that with this version of the reversing system, it is possible to obtain greater magnification by smoothly moving the additional lens away from the eyepiece. However, you won’t be able to get a strong magnification if you don’t have a very high-quality lens (for example, glass from glasses). The phenomenon of so-called “chromatic aberration” interferes, when the image is painted in rainbow shades.

This problem is solved in “purchased” optics by composing a lens from several lenses with different refractive indices. But you don’t care about these details: your task is to understand the circuit diagram of the device and build the simplest working model according to this scheme (without spending a penny).

You can obtain a wraparound system with two coaxial additional lenses by positioning them so that the eyepiece and these two lenses are spaced from each other at equal distances f.

Now you have an idea of ​​the telescope design and know the focal lengths of the lenses, so you begin to assemble the optical device. The simplest thing is to twist pipes (tubes) from sheets of whatman paper, securing them with rubber bands “for money”, and fix the lenses inside the tubes with plasticine. The inside of the pipes must be painted with matte black paint to prevent external exposure.

The result seems to be something primitive, but as a zero option it is very convenient: it’s easy to remake, change something. When this zero option exists, it can be improved for as long as desired (at least replace the Whatman paper with more decent material).

A factory-made telescope is quite expensive, so it is advisable to buy it if you are seriously interested in astronomy. And amateurs can try to assemble a telescope with their own hands.

As you know, there are two types of telescopes:

  • Reflex. In these devices, the role of light-collecting elements is performed by mirrors.
  • Refractory– equipped with an optical lens system.

DIY refracting telescope

The design of a refracting telescope is quite simple. At one end of the device there is a lens - a lens that collects and focuses light rays. At the other end there is an eyepiece - a lens that allows you to view the image that comes from the lens. The lens is placed in a main tube called the tube, and the eyepiece is placed in a smaller tube called the eyepiece assembly.

An ordinary telescope made from a magnifying glass

  1. Making the main pipe. Take a sheet of thick paper and roll it into a tube using a flat stick or a suitable pipe with a diameter of 5 cm. The paper inside should be painted black and not shiny. We make the pipe 1.9 meters long.
  2. Making an eyepiece tube. It should be put on the end of the main one. We roll it up from a sheet of paper 25 cm long and glue it. The inner diameter of the eyepiece tube must match the outer diameter of the main tube so that it moves effortlessly along it.
  3. Working with lenses. We make two lids from thick paper. We will place the first one where the lens will be, and we will attach the second one to the end of the eyepiece tube. In the middle of each cap we will make a hole with a diameter slightly smaller than the diameter of the lenses. We install the lenses with their convex side outward.

To take interesting photographs of the starry sky, you can attach a webcam to a telescope.

Telescope from binoculars

From ordinary eight-power binoculars you can build a telescope that provides magnification of over 100 times. Pipes can be glued together from whatman paper. Lenses are suitable from old filmoscopes or similar in magnification. We use the calculation of a simple telescope, and select the length of the device and the distance between the eyepiece lenses experimentally.

There is no need to disassemble the binoculars - the tubes are put directly on it. For ease of use, you can make a tripod. Such a telescope from binoculars allows you to see mountains and craters on the surface of the Moon, satellites of Jupiter, etc.

Conclusions

Making a homemade telescope at home is not particularly difficult. Even a high school student can do this kind of work. For a child, a device with a magnification of 30–100 times will be sufficient.

However, there are home craftsmen who can independently assemble a three-hundred-power high-quality telescope. Such skills come with experience and can be useful to those who are seriously interested in astronomy.

How does a telescope work?

Many people think that a telescope is just a big magnifying glass that magnifies everything, but in fact, a telescope is built like an eyeball. Its primary task is to collect and focus light.

As you know, light not only falls on objects, but also reflects from them. We are able to see objects because our eyes catch the light reflected from them. By the way, this is why we cannot see in complete darkness. The objective lens works in the same way, but it is more powerful, and therefore can collect much more light from distant objects. But the eyepiece is already designed to enlarge the resulting image.

Making Galileo’s telescope is not at all difficult - and even easier than it was for him, because the 17th century physicist did not have tape, PVA glue and other modern conveniences! Let's start with the most troublesome part: finding the lenses.

If you don't know how many diopters are in the lens, you can measure them yourself. You will need a ruler and a light source (for example, a flashlight or table lamp). Place the ruler so that its edge touches the wall - it will serve as a screen. Point the light directly at the lens. Do you see how it refracts the beam? Move the lens parallel to the ruler until the light on the screen converges to a point. The distance from the wall at which the lens ends up is called the focal distance. The number of diopters is calculated using the following formula:

For example, if there is 50 cm between the lens and the screen, that is, 1:2 m, then the optical power is 1:(1:2) - 2 diopters.

Assembling a telescope

1. As a lens, let’s take an ordinary magnifying glass of +2 diopters with a diameter of 100 mm - this can be found in a stationery store or even in your desk drawer. For the eyepiece, you will need to acquire a negative lens of –20 diopters with a diameter of 25–50 mm - sold in any optician. As an optical tube - this is the base of our telescope on which the lenses are attached - round boxes of chips, plastic pipes or simply thick sheets of paper rolled into a cylinder are suitable.

Selecting the magnification

Is it necessary to take exactly these lenses? Not at all! We have selected parameters that do not require a particularly long optical tube, but provide significant magnification. If you want to change it, select lenses according to the formula:

Our telescope has the following parameters: F = 0.5 m, f = 0.05 m, therefore, its magnification is 0.5 / 0.05 = 10 times.

Let's make the diameter of the hole a couple of millimeters larger than the diameter of the objective lens to make it easier to insert it. The length of the tube should be equal to the focal length of the lens - tape several cylinders together if necessary. In our case it is 50 cm.

2. Roll the paper into a cylinder. Using glue, attach the objective lens to the end of the optical tube with the convex side inward.

Advice:The darker the inside of the optical tube, the higher the image contrast. Paint it black or use dark paper.

3. We make a holder for a small lens - an eyepiece. This can be a plastic lid or a cardboard circle with a hole of the desired size.

4. Glue the lens holder to the other edge of the optical tube. The telescope is ready! Decorate to your liking.

A little history

Johann Liepershey

Did you know that the telescope was not invented by Galileo? He was “only” the first to decide to point it to heaven. In fact, a telescope is an ordinary telescope, like those used by sailors and travelers. Its invention is usually credited to the Dutchman Johann Liepershuy, who applied for a patent in 1608. Galileo assembled a copy of this device for himself a year later.

The design of the first telescope was very simple: two lenses mounted in a hollow tube. A lens is a large lens directed towards the object you want to look at (that's why it's a lens). And the lens you look directly into is called the eyepiece.

In the 17th century, lens telescopes ruled the show (they are also refractors, since they work due to refraction - refraction), but in the 18th century they were replaced by the invention of another great physicist - Isaac Newton. He replaced the objective lens with a concave mirror to avoid image error. Such telescopes are called reflectors.

Observing stars and other astronomical bodies in the sky is a very entertaining process. The planets of the solar system, satellites, constellations, “shooting stars” - all this is only a small part of the vast and completely unknown Universe. The most clearly visible is the Moon, the closest cosmic body to us, not counting man-made artificial satellites of the Earth. However, even the Moon is quite difficult to see in detail with the naked eye. For this purpose, mankind has invented a special device - a telescope, which allows you to “bring closer” the observed object and study it in more detail. Let's try to figure out how to make a simple telescope with your own hands.

All optical telescopes can be divided into two groups: refractor telescopes, which use lenses that refract and thereby collect light, and reflecting telescopes, which use mirrors as such an element. It is easier to make a refracting telescope with your own hands, since this requires collecting lenses, which are not difficult to find, unlike special collecting mirrors. We will make such a telescope with 50x magnification, for which we will need: thick paper (Whatman paper), cardboard, black paint, glue and two collecting lenses.

First, let's look at the structure of a simple refracting telescope. Its main part is the lens - a biconvex lens located in the front of the telescope and collecting radiation. Its main characteristics are: lens diameter (aperture) , the larger the aperture, the more radiation the telescope collects, that is, the greater its resolution, and, as a result, higher magnifications can be used; focal length of the lens. Another important part of a telescope is the eyepiece. The magnification of a telescope is calculated as a value equal to the ratio of the focal length of the lens to the focal length of the eyepiece ¸ and is expressed in multiples:

.

In addition, there is such a thing as the maximum useful magnification of a telescope, which is equal to twice the diameter of the lens , expressed in millimeters. It makes no sense to make a telescope with higher magnification, since most likely it will not be possible to see new details, and the overall brightness of the image will significantly decrease. Thus, if you need to make a telescope with 50x magnification, then the lens diameter must be at least 25 mm. But a small diameter reduces resolution, so for a 50x telescope it is advisable to use a lens with a diameter of 60 mm.

The minimum useful magnification of a telescope is determined by the diameter of its eyepiece , which should not exceed the diameter of the fully opened pupil of the observer’s eye, otherwise not all the light collected by the telescope will enter the eye and will be lost. The maximum pupil diameter of the observer's eye is usually 5-7 mm, so the minimum usable magnification is 10x (aperture times 0.15).

We proceed directly to the manufacture of the telescope. It will not be possible to make a telescope from large-sized Whatman paper, since Whatman paper does not have sufficient rigidity, which will lead to problems with adjusting the telescope. The optimal size is approximately 1m. Therefore, the focal length of the lens should also be about 1 m, which corresponds to an optical power of +1 diopter. For the lens, you need to make a pipe from whatman paper with a length of 60-65 cm and a diameter corresponding to the diameter of the objective lens (6 cm). The inside of the tube should be painted black before gluing to prevent excess radiation from entering the eyepiece. The lens can be secured in the lens tube using two toothed rims cut out of cardboard.

For the eyepiece, you need to make a tube 50-55 cm long. The lens and eyepiece tubes are also connected to each other using cardboard rims, which allow the eyepiece tube to move relative to the lens tube using little force. To provide a telescope with 50x magnification, the eyepiece lens must have a focal length of 2-3 cm.

The resulting telescope has one drawback - it gives an inverted image. To correct this, you will need another converging lens that has the same focal length as the eyepiece lens. An additional lens must be installed in the eyepiece tube.

When making a telescope, it should also be taken into account that in telescopes with high magnification, various diffraction phenomena are more pronounced, which significantly impairs visibility. This magnification is commonly used to observe features on the disks of planets and the Moon, as well as when observing double stars. Therefore, to reduce this effect, you need a diaphragm (a black plate with a hole 2–3 cm in diameter), which is placed in the place where the rays from the lens converge into focus. After this improvement, the image will become less bright, but clearer.

Using the proposed method, we suggest you solve the problem:

What should be the main parameters of a telescope with 100x magnification?

Many people consider a telescope to be a very complex device that cannot be made independently at home. This is true of modern devices with a very complex design, but making a simple telescope with your own hands is possible. In this article you will learn how to make a telescope in just a couple of hours.

Following the instructions, you can make a telescope with a magnification of 30, 50 or 100 times. All three variants have the same design and differ only in the objective lens and unfolded length.

You will need:

  • Whatman;
  • Glue;
  • Black ink or paint;
  • Two optical lenses.

If this is your first time assembling such devices, then first it is better to try to make a telescope with 50x magnification.

Lens

From a sheet of whatman paper we roll up a pipe 60-65 cm long. The diameter should be made slightly larger than the diameter of the objective lens. When using a standard spectacle lens, the diameter of the tube will be about 6 cm. Then unfold the sheet and paint the inside with black ink. Thus, the inner surface of the telescope will be black, this will eliminate the possibility of outside light (not from the object being observed).

Once the dimensions, diameter and one side of the sheet have been determined, you can roll the sheet and secure it with glue. An objective lens of +1 diopter should be secured at the end of the pipe using two cardboard rims with teeth (shown in the figure).

1 - objective lens,
2 - eyepiece lens,
3 - lens mount,
4 - tube mount for eyepiece lenses,
5 - additional lens for inverting the image,
6 - diaphragm

Eyepiece

The next step in making a telescope with your own hands is to create an eyepiece.
An eyepiece lens, for example, can be pulled out of a broken binocular. The focal length (f) of the lens should be 3 - 4 cm. This distance is determined as follows: direct light from a distant source (for example, the sun) onto the lens, move the lens away from the screen on which you are projecting the beam. The distance between the lens and the screen at which the light beam is focused into a small point and will be the focal length (f).

Roll a piece of paper into a tube of such diameter that the eyepiece fits tightly into it. If the lens has a metal frame, then no additional fastenings are needed.

The finished tube with eyepiece is secured in a large tube using two cardboard circles with holes in the center. The eyepiece tube should move freely, but with little effort.

The homemade telescope is ready. Only it has a small disadvantage - an inverted image. When observing celestial objects, this is not a disadvantage at all, but if you observe terrain objects, you will experience certain inconveniences. To flip the image, you need to install another lens with a focus of 3–4 cm into the eyepiece tube.

Telescope with 30x magnification no different from the one described above, except for the lens of + 2 diopters and length (about 70 cm, when extended).

Telescope with 100x magnification, will be about two meters long and will require a + 0.5 diopter lens. Such a homemade telescope will allow you to see “seas”, craters, plains filled with lava, and mountain ranges near the Moon. You can also find Mars and Venus in the sky, their size will be about a large pea. And if your vision is sharp, then among a large number of stars you can find Jupiter.

The image of such a powerful telescope with a small lens diameter may be spoiled by rainbow coloring. This is caused by the phenomenon of diffraction. This effect can be partially reduced using a diaphragm (a black plate with a hole 2–3 cm in diameter). The aperture is set at the point where the rays from the lens come into focus. This location is determined using the screen.

After this modification, the image will become clearer, but will lose a little brightness.

If you are assembling a two-meter telescope from whatman paper, you should know that it will bend under the weight of the lens, throwing off the settings. To maintain the geometry of the pipe, wooden slats should be attached on both sides.

This is how you can make a telescope with your own hands. Not the most powerful, but suitable for sparking interest in astronomy.

Interesting and fascinating observations for you.