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How to make an optical device at home. How to assemble a telescope with your own hands: a budget solution

Sometimes you find all sorts of rubbish in your bins. In dresser drawers in the country, in chests in the attic, among things under an old sofa. Here are grandma's glasses, here is a folding magnifying glass, here is a damaged peephole from the front door, and here are a bunch of lenses from disassembled cameras and overhead projectors. It’s a shame to throw it away, and all this optics sits idle, just taking up space.
If you have the desire and time, then try to make a useful thing out of this trash, for example, a spyglass. Do you want to say that you’ve already tried it, but the formulas in the help books turned out to be painfully complicated? Let's try again, using simplified technology. And everything will work out for you.
Instead of guessing by eye what will happen, we will try to do everything further according to science. Lenses are magnifying and minimizing. Let's divide all the available lenses into two piles. In one group there are magnifying ones, in the other group there are diminutive ones. The disassembled peephole from the door has both magnifying and minimizing lenses. Such small lenses. They will be useful to us too.
Now we will test all magnifying lenses. To do this, you need a long ruler and, of course, a piece of paper for notes. It would be nice if the sun was still shining outside the window. With the sun, the results would be more accurate, but a burning light bulb will do. We test lenses as follows:
-Measure the focal length of the magnifying lens. We place the lens between the sun and the piece of paper, and moving the piece of paper away from the lens or the lens away from the piece of paper, we find the smallest point of convergence of the rays. This will be the focus length. We measure it (focus) on all lenses in millimeters and write down the results, so that later we don’t have to worry about determining the suitability of the lens.
So that everything continues to be scientific, we remember a simple formula. If 1000 millimeters (one meter) is divided by the focal length of the lens in millimeters, we get the lens power in diopters. And if we know the diopters of the lenses (from an optics store), then dividing the meter by diopters we get the focal length. Diopters on lenses and magnifying glasses are indicated by a multiplication symbol immediately after the number. 7x; 5x; 2.5x; etc.
Such testing will not work with miniature lenses. But they are also designated in dioptres and also have a focus according to dioptres. But the focus will already be negative, but not at all imaginary, quite real, and we will now be convinced of this.
Let's take the longest focal length magnifying lens in our kit and combine it with the strongest reducing lens. The total focal length of both lenses will immediately decrease. Now let's try to look through both lenses assembled, diminutive to ourselves.
Now we slowly move the magnifying lens away from the diminutive lens, and in the end we may get a slightly enlarged image of the objects outside the window.
The mandatory condition here must be the following. The focus of the diminutive (or negative) lens must be smaller than the magnifying (or positive) lens.
Let's introduce new concepts. The positive lens, also known as the front lens, is also called the objective lens, and the negative or rear lens, the one closer to the eye, is called the eyepiece. The power of the telescope is equal to the focal length of the lens divided by the focal length of the eyepiece. If the division results in a number greater than one, then the telescope will show something; if it is less than one, then you will not see anything through the telescope.
Instead of a negative lens, short-focus positive lenses can be used in eyepieces, but the image will already be inverted and the telescope will be slightly longer.
By the way, the length of the telescope is equal to the sum of the focal lengths of the lens and eyepiece. If the eyepiece is a positive lens, then the focus of the eyepiece is added to the focus of the lens. If the eyepiece is made of a negative lens, then plus to minus is equal to minus and from the focus of the lens, the focus of the eyepiece is already subtracted.
This means the basic concepts and formulas are as follows:
-Lens focal length and diopter.
-Magnification of the telescope (the focus of the lens is divided by the focus of the eyepiece).
-The length of the telescope (the sum of the focal points of the lens and eyepiece).
THAT'S THE COMPLEXITY!!!
Now a little more technology. Remember, probably, that telescopes are made folding, from two, three or more parts - elbows. These knees are made not only for convenience, but also for specific adjustment of the distance from the lens to the eyepiece. Therefore, the maximum length of the telescope is slightly greater than the sum of the focuses, and the moving parts of the telescope allow you to adjust the distance between the lenses. Plus and minus to the theoretical pipe length.
The lens and eyepiece must be on the same (optical) axis. Therefore, there should be no looseness of the pipe elbows relative to each other.
The inner surface of the tubes must be painted matte (not shiny) black, or the inner surface of the tube can be covered with black (painted) paper.
It is desirable that the internal cavity of the telescope be sealed, then the pipe will not sweat inside.
And the last two tips:
-don’t get carried away with large magnifications.
-if you want to make a homemade telescope, then my explanations will probably not be enough for you, read special literature.
If you don’t understand what’s what in one book, take another, third, fourth, and in some book you will still get the answer to your question. If it happens that you don’t find the answer in books (or on the Internet), then Congratulations! You have reached a level where the answer is already expected from YOU.
I found a very interesting article on the Internet on the same topic:
http://herman12.narod.ru/Index.html
A good addition to my article is offered by the author from prozy.ru Kotovsky:
So that even such a small amount of work does not go to waste, we should not forget about the diameter of the lens, on which the exit pupil of the device depends, calculated as the diameter of the lens divided by the magnification of the tube.
For a telescope, the exit pupil can be about a millimeter. This means that from a lens with a diameter of 50 mm you can squeeze (by choosing a suitable eyepiece) 50x magnification. At higher magnification, the image will deteriorate due to diffraction and lose brightness.
For a “terrestrial” tube, the exit pupil must be at least 2.5 mm (preferably larger. The BI-8 army binoculars have 4 mm). Those. for “terrestrial” use, you should not squeeze more than 15-20x magnification from a 50 mm lens. Otherwise, the picture will darken and blur.
It follows from this that lenses with a diameter of less than 20 mm are not suitable for the lens. Perhaps 2-3x magnification is enough for you.
In general, a lens made from spectacle lenses is not comme il faut: meniscus distortions due to convex-concave. There must be a duplex lens, or even a triplex if it is short-focus. You can't just find a good lens among the trash. Perhaps there’s a “photo gun” lens lying around (super!), a ship’s collimator or an artillery rangefinder :)
About eyepieces. For a Galilean tube (an eyepiece with a diverging lens), you should use a diaphragm (a circle with a hole) with a diameter equal to the calculated size of the exit pupil. Otherwise, when the pupil moves away from the optical axis, there will be severe distortion. For a Kepler tube (converging eyepiece, the image is inverted), single-lens eyepieces produce large distortions. You need at least a two-lens Huygens or Ramsden eyepiece. Better prepared - from a microscope. As a last resort, you can use a camera lens (don't forget to fully open the blade aperture!)
About the quality of lenses. Everything from the door peepholes goes into the trash! From the remaining ones, choose lenses with anti-reflective coating (characteristic purple reflection). The absence of clearing is allowed on surfaces facing outward (toward the eye and the object of observation). The best lenses are from optical instruments: film cameras, microscopes, binoculars, photo enlargers, slide projectors - at worst. Don’t rush to disassemble finished eyepieces and objectives made from several lenses! It is better to use the whole thing - everything is selected in the best possible way.
And one more thing. At high magnifications (>20) it is difficult to do without a tripod. The picture is dancing - you can’t make out anything.
You should not try to make the pipe shorter. The longer the focal length of the lens (more precisely, its ratio to the diameter), the lower the requirements for the quality of all optics. This is why in the old days telescopes were much longer than modern binoculars.

I made the best homemade trumpet this way: a long time ago in Salavat I bought a cheap children's toy - a plastic spyglass (Galileo). She had 5x magnification. But she had a duplex lens with a diameter of almost 50 mm! (Apparently, substandard from the defense industry).
Much later, I purchased an inexpensive Chinese 8x monocular with a 21mm lens. There is a powerful eyepiece and a compact wrapping system on prisms with a “roof”.
I "crossed" them! I removed the eyepiece from the toy and the lens from the monocular. Folded it, stapled it. The inside of the toy was previously covered with black velvet paper. Got a powerful 20x compact pipe of high quality.

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?

Winter is a good time to watch the sky. In winter you can see many stars and planets, as well as the Milky Way. The Milky Way is very beautiful (visible only in a clear sky). It is visible to the naked eye. In a clear sky, excluding artificial satellites visible in the sky, the ISS (International Space Station) can be seen with the naked eye. It appears as a moving high intensity light source, similar to Venus. The author of this homemade product observed all this with his own eyes and after that decided to purchase a telescope, but discovered that it was a very expensive pleasure. So he decided to make a simple home telescope. To make it you will need PVC pipes and lenses.

Step 1: Theory

A telescope is used to see a distant object that is not visible to the naked eye. The telescope zooms in on a specific area. The field of view is reduced and focused on a small part, resulting in a more detailed viewing experience.

The main components are a large objective lens and a small eyepiece. The lens has a large diameter, which increases the ability to collect light. More light means a clearer image, and there is a long focal length for a magnifying effect. The eyepiece has a smaller diameter and shorter focal length (to provide high magnification). The lenses are convex.
The lens converts a parallel beam of light from infinity (at a far distance) to a single point. The eyepiece diverges from convergent light because our eye needs parallel rays (our eye has a convex lens). Using this arrangement we get an inverted image. For sky viewing, inversion is not a problem. The scaling effect (increase) is determined by the given equation:

magnification = focal length (lens) / focal length (eyepiece)

A telescope works by refracting light rays. It has chromatic fraying problems caused by different colors being focused at different points, causing bright objects to appear rainbow-colored. This problem is reduced in a reflecting telescope. It uses mirrors, so refraction does not work. But a reflecting telescope is difficult to build, so we will create a refracting telescope.

This telescope does not have higher magnification. It is made more for educational purposes, so it has disadvantages.

Step 2: Required Materials and Tools


Convex lens 8.5 cm diameter

Lens with focal length 27 cm

Eyepiece from an old binocular, diameter 3.5 cm, length 5 cm, focal length 2 cm

PVC pipe with a diameter of 100 mm and a length of 25 cm

PVC pipe with a diameter of 50 mm and a length of 8 cm

PVC reducer (adapter) from 100 mm to 50 mm - 1 pc.

PVC plug, diameter 50 mm - 1 pc.

Screws (as many as needed)

Basic tools and materials are shown in the figure.

Step 3: Preparing Materials




To assemble a homemade product, you first need to prepare all the necessary materials:

Lens parts

1. Cut a piece of PVC pipe with a diameter of 100 mm and a length of 17.5 cm using a hacksaw blade.
2. Cut a piece of PVC pipe with a diameter of 100 mm and a length of 2 cm using a hacksaw blade.
3. Cut 3 pieces 2 cm long.
4. Peel and trim edges using a small knife.

Eyepiece parts

1. Take 8 cm PVC pipe.
2. Peel and trim edges using a small knife.
3. Take a 5cm end cap and drill a hole in the center using a drill press or alternative method.
4. The hole size is 2.8 cm (using the diameter of the binocular eyepiece).

Step 4: Fixing the Lens





First you need to fix the lens in a PVC pipe. The lens has a smaller diameter than PVC pipe. Therefore, to reduce the diameter, it is necessary to place a 2 cm long piece of PVC into the pipe. The lens is placed 2 cm inside the tube to reduce glare from side lights entering the telescope.

1. First, cut PVC into a small width and remove a part to secure this piece inside the PVC pipe (2 cm inside from the edge).

2. Then another piece of PVC is cut and some part is removed to fit the first piece placed.

3. Make sure the piece is 2cm away from all positions, and then secure it with screws (screws do not go inside the PVC pipe).

4. Then place the lens and secure it using other small pieces of PVC and screws. This is shown in the photo.
5. Then attach the gearbox to it. Use screws to secure the structure if it becomes loose. Make sure the screws do not penetrate the PVC.

6. Be guided by photographs if it is not very clear. The images are taken step by step.

Step 5: Fixing the Eyepiece



1. Attach the eyepiece to the hole in the end cap using screws and metal strips.

2. Make sure the screws do not penetrate inside the eyepiece.

3. All actions are shown in the photo.

4. Connect a PVC adapter (reducer) with a diameter of 100/50 cm to the end cover and secure it with a screw.

Step 6: Assembling the Telescope






Make sure that the 100 cm pipe moves freely inside the gearbox.
If necessary, sand the surface of the PVC pipe.
The movement of the PVC pipe in the gearbox is used to accurately focus the telescope.

To adjust the focus, look at a distant object through the telescope and find a clear image. The sharp image point is the focus point. Secure this position with a screw to secure the telescope at its focus point.

Step 7: Tips for Selecting Lenses

It is difficult to find a person on the whole earth who is not at least a little interested in astronomy. This, naturally, requires the presence of a certain tool that would allow us to take a closer look at the mysteries of the starry sky. If you have a telescope or binoculars, then this is enough to admire the beauty of the starry sky. But even if there is strong interest, such devices cannot satisfy the request. Something more powerful is needed, that is, a telescope. But how to create it? Considering the question: “do it yourself?” and this article is dedicated to.

Introductory information

Purchasing a factory-made telescope will be quite expensive. Therefore, its purchase is appropriate in cases where there is a desire to engage in astronomy at least at an amateur level. But first, in order to gain basic knowledge and skills, and also to understand whether this science really seems like what most people think about it, it would be useful to create a homemade home telescope with your own hands. In many children's encyclopedias and various popular science publications you can find a description of the process of making a simple device that allows you to see craters on the Moon, the disk of Jupiter along with its four satellites, the rings and Saturn itself, the crescent of Venus, individual bright and large star clusters and nebulae. It should be noted that the weak point of such devices is the image quality, which cannot compete with factory-made devices.

A little theory

Before you start creating a telescope with your own hands at home, it’s worth understanding how this device works.

The two minimum required optical components are a lens and an eyepiece. The first one is designed to collect light. Its diameter determines what maximum magnification the finished device will have, and how faintly visible objects can be observed. An eyepiece is needed to magnify the image that is formed by the lens and to transmit the image to the human eye.

Deciding on the type

Depending on the device, there are different telescopes. The two most common types are reflectors and refractors. In the first case, a mirror acts as a lens, in the second, a lens system. At home, creating everything in the required quality for a reflector is quite problematic, due to the difficulty and precision of the manufacturing process. Whereas refractor lenses are easy to purchase at an optical store. As you can see, the difference between them is purely in design.

First try

The ratio of the focal length from the lens to the eyepiece is used to determine the magnification value. The scheme discussed below will provide an improvement in visual properties by approximately 50 times.

Initially, you need to stock up on a blank lens for glasses, the power of which is one diopter. This corresponds to a focal length of one meter. Usually their diameter is about 7 centimeters. This is exactly what the lens needs. It should be noted here that if you are interested in how to make a telescope with your own hands from glasses lenses, then you should admit that they are poorly suited for such non-targeted use. But you can use them if you wish. If you have a long-focus biconvex lens, then it is better to use it. Although a magnifying glass from a magnifying glass with a diameter of 3 centimeters or a lens from a microscope is also suitable for the role of an eyepiece.

For the body, you need to make two pipes from thick paper. The first (representing the main part) will be one meter long. A twenty-centimeter pipe is created for the eyepiece assembly. The short one is inserted into the long one. To make the body, you can use a wide sheet of whatman paper or a roll of wallpaper, roll it into a pipe in several layers and glue it with PVA. The number of layers is selected manually. It is necessary to achieve the effect of rigidity of the future device. In this case, the internal diameter of the main part must be equal to the size of the selected lens.

But that's not all

If the only question is how to make a telescope with your own hands at home, then you can get by solely with the above.

But for a better result, you cannot do without some nuances.

So, the lens must be mounted in the first pipe with the convex side outward using a frame. For this purpose, rings of comparable diameter and a thickness of a centimeter are suitable. Immediately after the lens, you need to install a disk - the diaphragm. Its specific difference is the presence in the center of a hole with a diameter of 2.5-3 centimeters. This must be done to reduce image distortion that is formed by a single lens. True, this approach reduces the amount of light that the lens collects. To improve the result, the lens should be installed as close to the edge of the pipe as possible. Then it’s the turn of the eyepiece. Where should I place it? It must be installed in the eyepiece assembly as close to the edge as possible. In this case, a cardboard mount would be ideal for the eyepiece. It is better to make the device in the form of a cylinder, the diameter of which is equal to the size of the selected lens. It is installed inside the pipe thanks to two fasteners (for example, disks). In this case, it is necessary to ensure that its diameter is commensurate with both the lens and the eyepiece unit.

Preparing the Telescope for Use

The device is focused by changing the distance between the lens and the eyepiece. This is achieved, in a mechanical sense, by ensuring the movement of the eyepiece unit located in the main tube. To fix the position, it is best to use friction. It should be noted that it is more convenient to focus on large and bright objects, such as nearby buildings, the Moon, bright stars (but not the Sun).

When creating a telescope, it should be taken into account that the lens and eyepiece should be parallel to each other, and their centers should be located on the same line. During the preparation stage, you can experiment with the diameter of the aperture hole in order to find the optimal one. For example, if you select a lens of 0.6 diopters and set the focal length to 1.7 meters (1/0.6), this will allow you to achieve greater magnification. True, you will have to work on the aperture hole. Namely, increase its size.

And after completing work on the first device, remember one simple truth: through a telescope you can look at the Sun only twice - first with your right eye, then with your left. Such a dangerous activity instantly damages your eyesight, so it is better not to engage in it.

Subtotal

It should be noted that the resulting design will be imperfect. Namely, it will give an inverted image. To correct this, it is necessary to use another converging lens, with the same focal length as the eyepiece. It is installed in a pipe near it. It would seem that now there should be no questions about how to make a telescope with your own hands with magnification. But this is far from the only correct approach.

You can use other schematic options, using glasses or telephoto lenses as a basis. This is a very broad field in which there are both completely green beginners and professional astronomers. Therefore, if a certain question or misunderstanding of something arises, do not be shy, calmly ask the question of interest. For this purpose today there are thematic circles, websites, forums, etc. After all, you just have to plunge into the world of astronomy - and numerous treasures of the starry sky will open to your eyes. In general, the practical information considered should be enough to create a simple device. If you want to design and implement something more complex, then you cannot do without high-quality theoretical training.

Required knowledge

You should always remember that the main characteristics are the size of the lens, eyepiece and focal length. This is alpha and omega, without which it is impossible to create a telescope. But at the same time, there are a large number of small moments that can significantly affect the final result. For example, the maximum usable magnification of a telescope. The value of this parameter is equal to twice the lens diameter (in millimeters). It makes no sense to make a device with high magnification, since, most likely, you will not be able to see new details. But the overall brightness of the image will suffer. Therefore, for devices with a fifty-fold magnification, it is not recommended to use lenses less than 2.5 centimeters. It should be noted that the option proposed above has indicators of 7 and 3 cm, which is well suited for a telescope with a quality of 50x. You can also take a 4-cm lens as an objective, but in this case the resolution of the optical device will decrease. Therefore, it is better to use the recommended values.

Experimenting with design

The option when a main pipe of one meter is created and an additional one of twenty centimeters is built into it is not all. The design can be adjusted to create other forms of telescopes. For example, a tube of 60-65 centimeters is used for the lens, and another one enters it at 10-15 cm for the eyepiece, the length of which is 50-55 cm.

Back to theory

The minimum usable magnification for a telescope depends on the diameter of the eyepiece. There is one very important nuance here! Its size should not exceed the diameter of the observer's fully dilated pupil. Otherwise, not all the light collected by the telescope will reach the eye: it will be lost, deteriorating the quality of the device. Thus, the maximum diameter of the pupil of the eye in an ordinary person does not exceed five to seven millimeters. Therefore, to find the minimum useful magnification, take 10x (aperture multiplied by 0.15). This interesting word, aperture, means an opening similar to a diaphragm, only slightly refined and advanced. This device is used in complex devices to obtain high-quality results. But this is for those who want to make a telescope with their own hands at home with serious characteristics for a more thorough study of the starry sky.

Conclusion

Well, this is the minimum that everyone needs to know in order to create their own device for studying the starry sky. It doesn’t matter what the first step is - you assemble a reflector telescope with your own hands or a refractor. The main thing is that if this is of interest, then you need to act in this direction - study, master new knowledge, practice, discover something new for yourself or even for the whole world - do not stop, and luck favors those who are purposeful.

But be aware that when making devices with higher magnification, diffraction phenomena will become more pronounced. This will lead to poor visibility. And finally, the task: what basic parameters should a telescope providing 1,000x magnification have?

The second part will show you how to design and build a pipe for this crafts.

The general view of the telescope is a symbiosis of ideas drawn from various forums that are devoted to the manufacture of various telescopic homemade and an optician for them.

When making this project, I was not trying to achieve maximum mobility by reducing weight. Instead, homemade was developed as a stationary telescope, which will be located in the attic. It was decided to build it entirely from wood. The advantage of this design is the closed housing, which will protect the optics from dust, and the massive weight will make it more stable in the wind.

Step 1: Choose a design

The design is almost entirely up to you. But there are several rules that should be followed:

  • The curvature of the primary mirror dictates the length of the tube.
  • Select a focuser before making the body.
  • Decide what the telescope will be used for: visual observation or astrophotography.

In my case it was easy to calculate the curvature of the mirror, since I did it with your own hands. If you bought a primary mirror, it probably came with some information (diameter and focal ratio). To get the "focal center", multiply the diameter by the focal ratio (often called F/D):

"Coordinate center" = Diameterx Focus attitude

In my case, F = 7.93 x 4.75 = 37.67 inches (95.68 cm). This is the distance from the mirror in which a clear image is reproduced. You can’t put your head in front of the mirror every time to block the light coming from the star, can you? This is why it is necessary to use a secondary mirror (called an elliptical) oriented at 45 degrees to reflect the light to the side.

The distance between this mirror and your eye will depend on the size of your focuser. If you choose a low profile focuser, the distance will be minimal and you will need a smaller mirror. If you choose a higher focuser, the distance will be greater and the elliptical mirror will need to be larger, thereby reducing the amount of light that is reflected from the main mirror.

The last thing you need to decide is what you want to use this telescope for: visual observation or astrophotography. For visual observation, we mount an alt-azimuth and a small elliptical mirror. For photography, you'll need a precision mount to cancel out the Earth's rotation, a 5cm focuser, and an oversized elliptical mirror to prevent vignetting on the image.

Step 4: Partitions and Boards

Now that you have made sure that all the boards fit together and the sizes are correct, we can begin gluing the partitions to the boards.

We glue the boards (one at a time) onto the partitions. This will ensure a more even filling of the tube. You can adjust the other boards to fit into the gaps (by sanding the edges with a plane and sandpaper).

Step 5: Smooth the Pipe

Now that the tube is glued, you need to treat the boards to make the surface smoother. You can use a plane and 120, 220, 400 and 600 grit sandpaper to get the wood as smooth as possible.

If you notice that some of the boards don't fit perfectly, make small wood inserts using wood glue and wood dust. Mix them together and cover the cracks with this mixture. Let dry and sand the glued areas.

Step 6: Focuser Hole

To place the Focuser you need to correctly calculate the positions. Let's use the site to find the distance between the optical axis of the focuser and the end of the tube.

Once you have measured the distance, use a bit larger in diameter than the focuser and drill a hole in the center on one side. Position the Focuser and mark the position of the screws with a pencil, then remove the Focuser. Now drill 4 holes in each corner.

You can see that my focal point was slightly larger than the width of the board, so I had to add 2 wedges on both sides to create a flat surface.

Step 7: Mirror Honeycomb

Step 12: Rocker Arm

The moving “wheels” are 1.2 times larger than the mirror.

The rocker is constructed from walnut and maple. Teflon pads make the telescope move smoother.

The sides of the rocker are mounted on round bases. Cut-out handles (on each side) help with transport.

Step 13: Wheel Azimuth

In order to rotate the tool from left to right, we need to add a vertical axis.


The base is made of plywood, mounted on 3 hockey pucks (reduces vibration). There is a central rod and 3 Teflon gaskets.

Step 14: Finished Telescope

You will need to find the center of gravity.

You will also need an eyepiece. The shorter the focal length, the higher the magnification. To calculate, use the formula:

Magnification = telescope focal length / eyepiece focal length

My 11mm eyepiece gives me 86x magnification.

To prevent dust from accumulating on the primary mirror, you will need a cap on the front end of the tube. A simple piece of plywood with a handle will be a great solution.

Thank you for your attention!