Typically, when you buy a telescope, you get simple but necessary accessories without which it cannot function: eyepieces, a Barlow lens, a wrapping prism or diagonal mirror and a finder. Typically, most amateur telescopes are equipped with such accessories.

But everything can always be done only with complete accessories, or not all necessary accessories are included in the kit. As a rule, expensive telescope models are equipped with only one eyepiece and require the purchase of the necessary set.

Eyepieces

An eyepiece is an element of the optical system necessary to change magnification. It is impossible to observe through a telescope without an eyepiece. To calculate the magnification of a telescope, you need to divide the focal length of the telescope by the focal length of the eyepiece. For example, the focal length of the telescope is 700 mm, and the focal length of the eyepiece is 10 mm, in this case, the magnification will be 70 times.

Eyepieces come in different classes and optical designs. Eyepieces can vary in viewing angle, and can be divided into simple, wide-angle and ultra-wide-angle. Also, a zoom eyepiece with variable focal length and magnification is very convenient.

Adjustment eyepieces and laser collimators will be useful to owners of mirror telescopes, because... Such telescopes require re-adjustment after almost every transportation. Only in this case will the reflecting telescope use its potential

When choosing an eyepiece, pay attention to the mounting diameter; it must match the mounting diameter of the focuser. Standard sizes: 0.96", 1.25", 2".

Barlow lenses

A Barlow lens is another popular telescope accessory. A Barlow lens is a diverging lens or several lenses that increases the focal length of the telescope several times, and accordingly, allows you to make the magnification of the telescope several times greater.

The Barlow lens is used only in conjunction with the eyepiece; the Barlow lens cannot be used separately.

Light filters

A light filter is also an important, and sometimes even necessary, accessory for observing through a telescope. Light filters for telescopes can be divided into several types: solar filters, color planetary filters, narrow-band filters for observing and photographing nebulae.

Solar filters are used to safely observe the solar disk. Under no circumstances do we recommend observing the Sun through a telescope that is not equipped with a special filter. By using special filters such as Seymour Solar and Baader AstroSolar, observations of the Sun become absolutely safe, because... solar filters cut off 99.999% of visible radiation from the sun. To observe the Sun safely, you must place a solar filter on the telescope lens. That is, the inner diameter of the solar filter must be equal to the outer diameter of the telescope tube. It is not safe to observe through an ocular solar filter as the sun's rays cause heat and can cause the filter to crack! Observing the Sun can cause heating and damage to the filter placed on the eyepiece.

The most budget-friendly option for a solar filter is to make a filter according to the diameter of the telescope using a special solar film. This film is also completely safe and provides a rich contrast image. Depending on the film manufacturer, the color of the solar disk when observed may vary (Seymour Solar – bright orange, Bader AstroSolar – white). Also, there is a difference between visual and photographic film. Suitable for safe visual observations only visual film.

Another option is ready-made glass solar filters, designed for a specific diameter of the telescope tube.

Color filters are used mainly for visual observations of planets. Such filters make the image of planets more contrast and highlight details on their surface. Color filters include a lunar filter of neutral gray or green color, which dims the brightness of the Moon, making observations more comfortable. Color filters are sold individually or in sets.

Colored filters for observing planets

Color filters They are 1.25" and 2" in diameter, threaded, and screw into the eyepiece barrel.

The red filter is used for daytime observations of Venus, observations of the polar caps on the surface of Mars, and blue clouds on Jupiter. The orange filter will be very useful for observing the Moon, for daytime observations of Mercury, detailing the details of the surface of Mars, belts, festoons on Jupiter. Yellow filter - enhances the contrast of the surface of Venus, enhances the visibility of seas and clouds on Mars, belts on Jupiter. Green – increases the contrast of details on the Moon, improves the contrast of details on Venus, useful for observing storms and the polar caps of Mars. Blue-blue - very useful for

Special narrow-band filters are filters that cut off certain regions of wavelengths, leaving a narrow bandwidth of radiation? making the image more contrast. Such filters are used both for visual observations and for astrophotography of deep space objects emitting in a certain spectrum.

In our store you can buy ready-made sets of accessories for telescopes.

In addition to the accessories listed, you may also need the following accessories:

• T2 adapter ring for shooting through a telescope at direct focus
• Special astronomical camera
• Smartphone holder for photographing through the eyepiece phone for photographing through the eyepiece
• Telescope case
• Laser collimator for telescope alignment
• Other accessories

Telescope.

A telescope is an instrument designed to observe celestial bodies.

Before the telescope came along, the spotting scope was invented, created by the Dutch master John Lippershey in 1808. But the first who guessed to point the telescope into the sky was G. Galileo. In 1609, he “turned” the spotting scope into a telescope, and this telescope became a spotting scope with 3x magnification. In the same year, Galileo built a telescope with 8x magnification. Later, Galileo was able to create a telescope that gave a magnification of 32x. Galileo called the invention "perspicillum" (directly translated into Russian - "glass"). The term "telescope" was coined in 1611 by the Greek mathematician Giovanni Demisiani..

There are different types of telescopes:
1. gamma telescopes;
2. radio telescopes;
3. X-ray telescopes;
4. optical telescopes.

1. Gamma-ray telescopes.
These are telescopes that use gamma waves to explore space. Astronomical gamma rays appear in
studies of astronomical objects with a short wavelength of the electromagnetic spectrum. Most gamma ray sources are actually gamma ray burst sources, which emit only gamma rays for a short period of time ranging from a few milliseconds to a thousand seconds before dissipating into space. Gamma-ray telescopes study pulsars, neutron stars and black hole candidates in active galactic nuclei.

2. Radio telescopes
Their purpose is to receive radio emissions from celestial objects and study their characteristics: coordinates, radiation intensity, etc. In order to receive a clear signal from objects, radio telescopes should preferably be located far from the main populated areas in order to minimize electromagnetic interference from broadcast radio stations, television, radars and other emitting devices. Placing a radio observatory in a valley or lowland can protect it even better from the influence of man-made electromagnetic noise. There are amateur astronomers who use radio telescopes. Most often these are telescopes made by hand.

3. X-ray telescopes.
Designed for observing distant objects in the X-ray spectrum. To operate properly, they must be raised above the Earth's atmosphere, which is opaque to X-rays. Therefore, telescopes are placed in Earth orbits.

4. Optical telescopes.
What is an optical telescope? This is a pipe mounted on a mount, which is equipped with various axes to point the pipe at the object of observation. The telescope has a lens and an eyepiece. The rear focal plane of the lens is aligned with the front focal plane of the eyepiece. Instead of an eyepiece, photographic film or a matrix radiation receiver can be placed in the focal plane of the lens. In this case, the telescope lens, from an optical point of view, is a photographic lens. The telescope is focused using a focusing device.

According to their optical design, telescopes of this type are divided into:

• Lens (refractors) - an optical telescope that uses a system to collect light
  lenses The operation of such telescopes is due to the phenomenon of refraction (refraction). Refractors contain two main components: a lens objective and an eyepiece.
• Mirror (reflector) - an optical telescope that uses mirrors as light-collecting elements.
• Mirror-lens telescopes (catadioptric) are a telescope in which the image is formed by a complex lens containing both mirrors and lenses.

> Types of telescopes

All optical telescopes are grouped according to the type of light-gathering element into mirror, lens and combined. Each type of telescope has its own advantages and disadvantages, therefore, when choosing optics, you need to take into account the following factors: conditions and purposes of observation, requirements for weight and mobility, price, level of aberration. Let us characterize the most popular types of telescopes.

Refractors (lens telescopes)

Refractors These are the first telescopes invented by man. In such a telescope, a biconvex lens, which acts as an objective, is responsible for collecting light. Its action is based on the main property of convex lenses - the refraction of light rays and their collection at focus. Hence the name - refractors (from the Latin refract - to refract).

It was created in 1609. It used two lenses to collect the maximum amount of starlight. The first lens, which acted as a lens, was convex and served to collect and focus light at a certain distance. The second lens, playing the role of an eyepiece, was concave and was used to transform the converging light beam into a parallel one. Using the Galilean system, it is possible to obtain a direct, non-inverted image, the quality of which is greatly affected by chromatic aberration. The effect of chromatic aberration can be seen as false coloration of details and edges of an object.

The Kepler refractor is a more advanced system that was created in 1611. Here, a convex lens was used as an eyepiece, in which the front focus was combined with the rear focus of the objective lens. As a result, the final image was upside down, which is not important for astronomical research. The main advantage of the new system is the ability to install a measuring grid inside the pipe at the focal point.

This design was also characterized by chromatic aberration, but the effect could be neutralized by increasing the focal length. That is why telescopes of that time had a huge focal length with a tube of the appropriate size, which caused serious difficulties when conducting astronomical research.

At the beginning of the 18th century, it appeared, which is still popular today. The lens of this device is made of two lenses made from different types of glass. One lens is converging, the second is diverging. This structure can significantly reduce chromatic and spherical aberration. And the telescope body remains very compact. Today, apochromatic refractors have been created in which the influence of chromatic aberration is reduced to the possible minimum.

Advantages of refractors:

• Simple design, ease of operation, reliability;
• Fast thermal stabilization;
• Undemanding to professional service;
• Ideal for exploring planets, the Moon, double stars;
• Excellent color rendering in apochromatic version, good in achromatic version;
• System without central shielding from diagonal or secondary mirror. Hence the high contrast of the image;
• No air flow in the pipe, protecting the optics from dirt and dust;
• One-piece lens design that does not require adjustments by the astronomer.

Disadvantages of refractors:

• High price;
• Large weight and dimensions;
• Small practical aperture diameter;
• Limitations in the study of dim and small objects in deep space.

Name of mirror telescopes - reflectors comes from the Latin word reflectio - to reflect. This device is a telescope with a lens, which serves as a concave mirror. Its task is to collect starlight at a single point. By placing the eyepiece at this point, you can see the image.

One of the first reflectors ( Gregory telescope) was invented in 1663. This telescope with a parabolic mirror was completely free from chromatic and spherical aberrations. The light collected by the mirror was reflected from a small oval mirror, which was fixed in front of the main one, in which there was a small hole for the output of the light beam.

Newton was completely disappointed in refracting telescopes, so one of his main developments was a reflecting telescope, created on the basis of a metal primary mirror. It reflected light of different wavelengths equally, and the spherical shape of the mirror made the device more accessible even for self-production.

In 1672, astronomer Laurent Cassegrain proposed a design for a telescope that looked like Gregory's famous reflector. But the improved model had several serious differences, the main one being a convex hyperbolic secondary mirror, which made the telescope more compact and minimized central shielding. However, the traditional Cassegrain reflector turned out to be low-tech for mass production. Mirrors with complex surfaces and uncorrected coma aberration are the main reasons for this unpopularity. However, modifications of this telescope are used today all over the world. For example, the Ritchie-Chretien telescope and a lot of optical instruments based on the system Schmidt-Cassegrain and Maksutov-Cassegrain.

Today, the name “reflector” is commonly understood as a Newtonian telescope. Its main characteristics are a small spherical aberration, the absence of any chromatism, as well as non-isoplanatism - a manifestation of coma close to the axis, which is associated with the inequality of individual annular zones of the aperture. Because of this, the star in a telescope does not look like a circle, but like some kind of projection of a cone. At the same time, its blunt round part is turned from the center to the side, and the sharp part is turned, on the contrary, towards the center. To correct the coma effect, lens correctors are used, which should be fixed in front of the camera or eyepiece.

“Newtons” are often performed on a Dobsonian mount, which is practical and compact in size. This makes the telescope a very portable device, despite the size of the aperture.

Advantages of reflectors:

Affordable price;

• Mobility and compactness;
• High efficiency when observing dim objects in deep space: nebulae, galaxies, star clusters;

Maximum brightness and clarity of images with minimal distortion.

Chromatic aberration is reduced to zero.

Disadvantages of reflectors:

• Stretch of the secondary mirror, central shielding. Hence the low contrast of the image;
• Thermal stabilization of a large glass mirror takes a long time;
• An open pipe without protection from heat and dust. Hence the low image quality;
• Regular collimation and alignment are required and may be lost during use or transport.

Catadioptric telescopes use both mirrors and lenses to correct aberration and construct an image. Two types of such telescopes are in greatest demand today: Schmidt-Cassegrain and Maksutov-Cassegrain.

Instrument design Schmidt-Cassegrain(SHK) consists of spherical primary and secondary mirrors. In this case, spherical aberration is corrected by a full-aperture Schmidt plate, which is installed at the entrance to the pipe. However, some residual aberrations remain here in the form of coma and field curvature. Their correction is possible using lens correctors, which are especially relevant in astrophotography.

The main advantages of devices of this type relate to minimal weight and a short tube while maintaining an impressive aperture diameter and focal length. At the same time, these models are not characterized by stretching of the secondary mirror mounting, and the special design of the pipe prevents the penetration of air and dust inside.

System development Maksutov-Cassegrain(MK) belongs to the Soviet optical engineer D. Maksutov. The design of such a telescope is equipped with spherical mirrors, and a full-aperture lens corrector, the role of which is a convex-concave lens - a meniscus, is responsible for correcting aberrations. That is why such optical equipment is often called a meniscus reflector.

The advantages of MC include the ability to correct almost any aberration by selecting the main parameters. The only exception is higher order spherical aberration. All this makes the scheme popular among manufacturers and astronomy enthusiasts.

Indeed, all other things being equal, the MK system gives better and clearer images than the ShK scheme. However, larger MK telescopes have a longer period of thermal stabilization, since a thick meniscus loses temperature much more slowly. In addition, MKs are more sensitive to the rigidity of the corrector mount, so the telescope design is heavier. This is associated with the high popularity of MK systems with small and medium apertures and ShK systems with medium and large apertures.

Telescope structure

In the 20th century, astronomy made many steps in studying our Universe, but these steps would have been impossible without the use of such complex instruments as telescopes, the history of which goes back hundreds of years. The evolution of the telescope took place in several stages, and I will try to talk about them.

Since ancient times, humanity has been yearning to find out what is there in the sky, beyond the Earth and invisible to the human eye. The greatest scientists of antiquity, such as Leonardo da Vinci, Galileo Galilei, attempted to create a device that would allow one to look into the depths of space and lift the veil of mystery of the Universe. Since then, many discoveries have occurred in the field of astronomy and astrophysics. Every person knows what a telescope is, but not everyone knows how long ago and by whom the first telescope was invented, and how it was designed.

A telescope is a device designed to observe celestial bodies.

In particular, a telescope refers to an optical telescopic system not necessarily used for astronomical purposes.

There are telescopes for all ranges of the electromagnetic spectrum:

b optical telescopes

b radio telescopes

b x-ray telescopes

gamma-ray telescopes

Optical telescopes

A telescope is a tube (solid, frame or truss) mounted on a mount equipped with axes for pointing at and tracking an object of observation. A visual telescope has a lens and an eyepiece. The rear focal plane of the lens is aligned with the front focal plane of the eyepiece. Instead of an eyepiece, photographic film or a matrix radiation receiver can be placed in the focal plane of the lens. In this case, the telescope lens, from an optical point of view, is a photographic lens. The telescope is focused using a focuser (focused device). telescope space astronomy

According to their optical design, most telescopes are divided into:

b Lens (refractors or diopter) - a lens or lens system is used as a lens.

b Mirror (reflector or catoptric) - a concave mirror is used as a lens.

b Mirror-lens telescopes (catadioptric) - a spherical mirror is used as a lens, and a lens, lens system or meniscus serves to compensate for aberrations.

How to choose a good optical instrument?

As soon as a person establishes visual contact with space, he seeks an opportunity to look at everything that he sees much closer, to examine as many details as possible. This is what a telescope is designed for, how to choose it correctly?

Nowadays, so many different designs and models have been created that the buyer is at a loss for a long time - not knowing where to start buying. To begin with, of course, you should decide what you want to see in it and under what conditions you will observe it all. It is imperative to evaluate the living conditions in order to allocate a place for it, and material capabilities, that is, the funds that you can afford to pay for it. However, for the same amount you can buy two different tools.

Types of telescopes

In order to see the galaxy and nebulae, the largest aperture is needed. The usual dimensions of refractor rulers, for some reason, end at around 150 mm. Newtonian telescopes are most suitable for these purposes.

Photographs of planets are most often used using catadioptric telescopes, but they will be unsuitable for photographing a weakly extended object due to the small aperture.

Refractors are very suitable for observing star fields and double stars. You can also use them to view the moon and planets.

Conclusion

The mistake many buyers make is wanting to buy one telescope once and for all. You need to understand that each tool is intended for different objects, performs its role and will reveal to you different secrets of our universe. Of course, the enjoyment of your excursion through space will largely depend on you, and not on the telescope. Using even inexpensive tools, you can make your research interesting and unforgettable.

Video guide that describes in detail how to choose a telescope