Telescope is a visual optical instrument used to observe distant objects. It can enlarge the small opening angle of distant objects according to a certain proportion, so that they have a larger opening angle in the image space, and make the objects that were invisible or unclear to the naked eye become clear. Therefore, the telescope is an indispensable tool in astronomy and ground observation. It is an optical system that makes the incident parallel beams pass through the objective lens and eyepiece and still exit in parallel. According to the principle of telescope, it is generally divided into three types.

An instrument for observing distant objects by collecting electromagnetic waves. In daily life, telescopes mainly refer to optical telescopes. But in modern astronomy, astronomical telescopes include radio telescopes, infrared telescopes, X-ray telescopes and gamma-ray telescopes. In recent years, the concept of astronomical telescope has been further extended to gravitational waves, cosmic rays, dark matter and other fields.

In our daily life, an optical telescope is usually a cylindrical optical instrument, which focuses light through the refraction of a lens, or through the reflection of concave mirror, or through magnifying an eyepiece. Optical telescopes in daily life are also called "thousand-mile mirrors". It mainly includes amateur astronomical telescopes, theater telescopes and military binoculars.

[Edit this paragraph] Introduction

The commonly used binoculars need to add a prism system in order to reduce the volume and flip the inverted image. Prism system can be divided into Bohan prism system and Paul prism system according to different forms. The principles and applications of the two systems are similar.

Small hand-held telescope for personal use should not use too large magnification, which is generally 3 ~ 12 times. If the magnification is too large, the image definition becomes worse and the jitter is serious. Telescopes larger than 12 times are generally fixed by tripod or other means.

A telescope that uses a lens-cutting mirror is called a refractive telescope. Even if the lens barrel is lengthened and the lens is machined accurately, the chromatic aberration cannot be eliminated. Newton once thought that the chromatic aberration of refractive telescope was hopeless, but it turned out to be too pessimistic. 1668, he invented the reflective telescope, which solved the problem of chromatic aberration. The first reflective telescope was very small. The aperture of the mirror in the telescope was only 2.5 cm, but the profit and loss of Jupiter's satellite and Venus could be clearly seen. 1672, Newton made a larger reflecting telescope and gave it to the Royal Society, which is still kept in the library of the Royal Society. 1733, an Englishman Hal made the first achromatic refraction telescope. 1758, the same telescope was made in Boland, London. He made convex lenses and concave lenses from glasses with different refractive indexes to offset the colored edges they formed. However, it is not easy to make a big shot. At present, the largest refracting telescope in the world has a diameter of 102 cm and is installed at the Addis Observatory. 1793, William Herschel of England made a reflective telescope. The reflector has a diameter of 1 30cm, is made of copper-tin alloy and weighs1ton. The reflecting telescope made in william parsons, England in 1845, the diameter of the reflector is1.82m .. 19 17, and the Hooke telescope was built at Mount Wilson Observatory in California, USA. Its primary mirror aperture is 100 inch. It was with this telescope that Edwin Hubble discovered the amazing fact that the universe is expanding. 1930, BernhardSchmidt, Germany, combines the advantages of refractive telescope and reflecting telescope (refractive telescope has small aberration but chromatic aberration, and the larger the size, the more expensive it is; Reflective telescope has no chromatic aberration, and its cost is low. The reflector can be made large, but there is chromatic aberration), and the first folding reflective telescope is made.

history

The idea of Hubble Space Telescope can be traced back to 1946. This telescope was designed, built and launched in A.D. 1970, and cost 2 billion dollars. NASA Marshall Space Flight Center is responsible for the design, development and construction of Hubble Space Telescope. NASA Goddard Space Flight Center is responsible for scientific equipment and ground control. Perkin Elmer is in charge of making the lens. Lockheed is responsible for building telescope mirrors.

Refraction telescope is a kind of telescope with lens cutting mirror. There are two kinds: galileo telescope with concave lens as eyepiece; Kepler telescope with convex lens as eyepiece. Because the chromatic aberration and spherical aberration of Dan Toujing objective lens are quite serious, modern refractive telescopes generally use two or more lens groups. Among them, the double-lens objective lens is the most widely used. It consists of a convex lens made of crown glass and a concave lens made of flint glass, which are very close. It can completely eliminate the position chromatic aberration of two specific wavelengths and weaken the position chromatic aberration of other wavelengths.

When certain design conditions are met, spherical aberration and coma can also be eliminated. Due to the influence of aberration such as residual chromatic aberration, the relative aperture of the dual-lens objective is relatively small, generally115-1/20, and rarely larger than 1/7, so the available field of view is not large. A double-lens objective with a diameter less than 8 cm can glue two lenses together, which is called a double-glued objective, and a double-separated objective with a certain gap is called a double-glued objective. In order to increase the relative aperture and field of view, a multi-lens objective group can be used. For galileo telescope, the structure is very simple and the light energy loss is less. The lens barrel is short and light. And it is still a positive image, but the magnification is small and the field of vision is narrow. It is generally used for theater mirrors and toy telescopes. For Kepler telescope, it is necessary to add a prism group or lens group behind the objective lens to rotate the image, so that the eyes can observe the positive image. Refractive telescopes generally adopt Kepler structure. Because the imaging quality of refractive telescope is better than that of reflective telescope, it has a large field of view and is convenient to use and maintain. Most small and medium-sized astronomical telescopes and many special instruments use refractive systems, but the manufacture of large refractive telescopes is much more difficult than that in reflecting telescope. Because it is difficult to smelt high-quality lenses with large caliber, and there is a problem of glass absorbing light, large-caliber telescopes all adopt reflection type.

(The following is a detailed introduction)

galileo telescope

The objective lens is a convergent lens and the eyepiece is a telescope with a divergent lens. The real image formed by the refraction of light through the objective lens is in the focus behind the eyepiece (near the back of the human objective lens). This image is a virtual image to the eyepiece, so it is refracted by the eyepiece to form an enlarged upright virtual image. The magnification of galileo telescope is equal to the ratio of the focal length of the objective lens to the focal length of the eyepiece. Its advantage is that the lens barrel is short and can stand upright, but the field of vision is relatively small. A device that juxtaposes two galileo telescope with low magnification and uses a bolt button in the middle to adjust its definition is called a "drama viewing mirror"; Because it is easy to carry, it is often used to watch performances. The telescope invented by Galileo plays an important role in the history of human understanding of nature. It consists of a concave lens (eyepiece) and a convex lens (objective lens). Its advantage is simple structure, which can directly form an upright image.

Kepler telescope

This principle consists of two convex lenses. Because there is a real image between the two, the reticle is easy to install and has excellent performance, so at present, military telescopes, small astronomical telescopes and other professional telescopes all adopt this structure. But the imaging of this structure is inverted, so an upright system should be added in the middle.

There are two types of imaging systems: prism imaging system and lens imaging system. Our common typical binoculars with wide front and narrow back adopt a double right-angle prism imaging system. The advantage of this system is that the optical axis is folded twice at the same time, which greatly reduces the volume and weight of the telescope. It is expensive to use a complex set of lenses to invert the image. The Russian 20×50 three-section telescope not only adopts a well-designed lens upright system.

A large telescope for astronomical observation outside the earth's atmosphere. Because it avoids the influence of the atmosphere and will not be distorted by gravity, it can greatly improve the observation ability and resolution, and even make some optical telescopes observe near infrared and near ultraviolet at the same time. However, there are many new strict requirements in manufacturing, for example, the mirror machining accuracy should be within 0.0 1 micron, and all components and mechanical structures should be able to withstand the vibration and overweight during launch, but they should be as light as possible to reduce the launch cost. The first space telescope, also known as Hubble telescope, was put into orbit 600 kilometers above the ground by the American space shuttle Discovery on April 24th, 1990. Its overall shape is cylindrical, with a length of 13m and a diameter of 4m. The front end is a telescope, and the back half is an auxiliary instrument, with a total weight of about11t. The telescope has an effective aperture of 2.4 meters and a focal length of 57.6 meters. The observation wavelength ranges from ultraviolet 120 nm to infrared 1200 nm, and the cost is1500 million USD. The resolution of the original design is 0.005, which is 100 times that of the ground telescope. However, due to a small negligence in manufacturing, it was not until the last day that there was a big spherical error in the instrument, which seriously affected the observation quality. 19931February 2 ~ 13, the American space shuttle Endeavour carried seven astronauts, successfully replaced 1 1 components for Hubble, completed the repair work, and created the history of human repairing large spacecraft in space. The successfully repaired Hubble telescope will continue to provide information on the depth of the universe for 10 years. 199 1 In April, the United States launched the second space telescope, which is a device for observing gamma rays. Total weight 17 ton, power consumption 1.52 watt, signal transmission rate 17000 bit/s, carrying four groups of detectors, with angular resolution of 5'~ 65438. Its service life is about 2 years.

Gemini telescope

Gemini telescope is an international equipment led by the United States (50% in the United States, 25% in Britain, 5% in Canada, 5% in Chile, 2.5% in Argentina and 2.5% in Brazil), which is implemented by the Astronomical Union of American Universities (AURA). It consists of two 8-meter telescopes, one in the northern hemisphere and the other in the southern hemisphere, for all-day systematic observation. The primary mirror is controlled by active optics, the secondary mirror is quickly corrected by tilting mirror, and the infrared region will approach the diffraction limit through adaptive optical system.

solar telescope

Corona is a thin and weak outer atmosphere around the sun, and its structure is complex. It can only be appreciated in a short time when the total solar eclipse occurs, because the light in the sky is always scattered or diffused into the telescope from all directions.

1930, the first corona instrument developed by French astronomer Leo was born. This instrument can effectively block the sun and scatter very little light, so it can successfully take photos of the corona on any day when the sun shines. Since then, the world observation corona has gradually appeared.

The coronagraph is just a kind of solar telescope. Since the 20th century, due to the need of practical observation, various solar telescopes have appeared, such as chromosphere telescope, solar tower, combined solar telescope and vacuum solar telescope.

Infrared telescope

An infrared telescope that receives infrared radiation from celestial bodies. The shape and structure are similar to those of optical mirrors, and some of them can be used for infrared observation and optical observation. The terminal equipment of infrared observation is completely different from optical observation, which requires modulation technology to suppress background interference and interference method to improve its resolution. Infrared observation imaging is also very different from optical imaging. Because there are only seven narrow infrared "windows" in the earth's atmosphere, infrared telescopes are often placed on high mountains. Most of the better ground-based infrared telescopes in the world are installed in Monaque, which is the research center of infrared astronomy in the world. Keck telescope, built in 199 1, is the largest infrared telescope. Its aperture is 10 meter, which can be used for both optical and infrared purposes. In addition, infrared telescopes can be installed on high-altitude balloons. The maximum aperture of the infrared telescope on the balloon is 1 m, but the effect is comparable to that of some infrared telescopes with larger aperture on the ground.

Instant replay

Instant replay-high performance digital imaging telescope.

It was rated as one of the "100 scientific and technological innovations" by mainstream scientific and technological media. Because of its simple structure and clear imaging, it can achieve the effect of super telephoto with a small body length, and with advanced digital functions, it can achieve clearer camera and video recording functions, which greatly broadens the application field of the telescope and can be widely used in reconnaissance, bird watching, electric power, wildlife protection and so on.

The digital telescope also has the functions of taking photos, video recording and image transmission. Long-term observation of traditional telescopes may cause eye discomfort, but users of digital telescopes can easily zoom in through the LCD screen. If the display screen is too small to meet the requirements, they can directly connect to the TV or mp4 through the TV interface, or even directly connect to the computer through the usb cable to realize online recording or image transmission. Of course, the smoothness and color of video are far less than natural colors. Even so, as a high-end telescope, digital telescope also provides comfortable direct observation function!

Digital telescope has the function of taking pictures, which can save many unforgettable moments in life. In the United States, this product is widely favored by sports coaches, scouts, bird hunters, wildlife observers, hunting enthusiasts and any photographer and cameraman. In China, the best remote control shooting equipment in this field is watchto series, especially WT-20A series and 30B series. At present, many domestic public security, military police and wildlife protection have taken advantage of the digital telescope and applied it to their work, especially the public security department, which can conveniently take photos and collect evidence remotely.

Digital camera with built-in 5/kloc-0.0 million pixel coms sensor. It can quickly and simply switch from static high-resolution photos (2594* 1786) to 30-second continuous photography. This will ensure that you get the best results. Photos and videos are stored in memory or sd card, and can be viewed, deleted, watched on TV or downloaded to the computer without installing other software. At present, the magnification of the main popular optical parts is 35 times and 60 times, and can be switched between high magnification and low magnification! Windows 2000, XP, or Mac do not require drivers. Windows 98/98SE needs to install drivers).

Maksutov telescope

China entry sign Sutov telescope

Foreign entry Maksutov telescope

Author Yang Shijie

1940 At the beginning of the year, Maksutov, a Soviet optician, invented a folding reflecting telescope, hence its name. Bowers, a Dutch optician, also independently invented a similar system almost at the same time, so it is sometimes called Maksutov-Bowers system.

The optical system of Maksutov telescope is similar to Schmidt telescope, which consists of a concave spherical reflector and a lens added in front to correct spherical aberration. The corrective lens is spherical, and the radius of curvature of its two surfaces is not much different, but it has considerable curvature and thickness. The lens is meniscus, so this system is sometimes called meniscus system. Proper selection of the radius of curvature and thickness on both sides of the lens can make the meniscus lens produce enough spherical aberration to compensate the concave spherical mirror and meet the achromatic condition. By properly adjusting the distance between the meniscus lens and the spherical mirror in the whole system, coma can be corrected: the astigmatism of the optical system of the Maksutov telescope is very small, but the field curvature is relatively large, so a curved negative conforming to the focal plane must be used. The central part of the second surface of the meniscus lens can be ground into a spherical surface with a longer radius of curvature (or a cemented lens) to form a Maksutov-Casglin system with a required relative aperture, or the central part of the meniscus lens can be directly aluminized to form a Maksutov-Casglin system. The main advantages of Maksutov telescope are: all surfaces in the system are spherical and easy to manufacture; Under the same aperture and focal length, the length of the lens barrel is shorter than that of Schmidt telescope. The disadvantages are: compared with the same type of Schmidt telescope, the field of view is slightly smaller; The thickness of the meniscus lens is relatively large, generally about110 of the aperture, which limits the increase of the aperture.

At present, the largest Maksutov telescope is located at the Toumani Observatory in Abbas, Soviet Union. The aperture of meniscus lens is 70cm, the diameter of spherical mirror is 98cm, and the focal length is 2 10cm.

[Edit this paragraph] Common parameters

1. Magnification: Generally, the ratio of the eyepiece viewing angle to the incident angle of the objective lens is used as the index of telescope magnification, but it is usually calculated by the ratio of the focal length of the objective lens to the focal length of the eyepiece, indicating the degree of magnification of the telescope on the scene. For example, a telescope with a magnification of 100 times indicates the effect of observing the scene at a distance of 100 meters from the observer without using a telescope.

2. The field of view indicates the visible scene range of the product at 1000m, such as 126m/ 1000m, which means that the telescope can observe the field of view at a distance of 1000m from the observer.

3. Diameter of entrance pupil

4. Pupil diameter

Step 5 solve

6. The dusk coefficient is published by Zeiss Optical Company in Germany. It reflects the observation efficiency of telescopes with different calibers and magnifications in dark light. Calculation method: the product of telescope magnification and aperture is square.

Step 7 show the distance

8. Parallelism of optical axis

9, like to tilt

[Edit this paragraph] Most telescope

The largest telescope

The size of a telescope is mainly measured by its aperture. In order to study and observe celestial bodies more carefully and look for darker celestial bodies, people have been trying to improve the caliber of telescopes for many years. But different telescopes have different requirements for aperture. At present, the largest reflecting telescope in the world is the 6-meter telescope built by the Soviet Union 1975. The 5m reflecting telescope, which surpasses the Paloma Mountain Observatory in the United States, has been called "the best in the world" for 30 years. Its rotating parts total 800 tons, which is 200 tons heavier than that of the United States. 1978, an American multi-mirror telescope with a combined diameter of 4.5m was put into trial operation. This telescope consists of six identical Ka seglin telescopes, each with a diameter of1.8m.. The six telescopes are arranged in a hexagonal shape around the central axis, and the six beams will converge to a six-sided combiner through a flat mirror, and then the six beams will converge to the same focus. Multi-mirror telescope has the advantages of large aperture, short lens barrel, small floor space and low cost. At present, the largest optical telescope is Keck telescope, with a diameter of 10 meter.

At present, the largest refracting telescope in the world is the Schmidt telescope installed at the Taudenberg Observatory in Germany, with a calibration aperture of 1.35m and a primary mirror aperture of 2 m ... The refracting telescope in Germany also surpasses the largest Schmidt telescope in the United States. On the telescope, the two "world firsts" of the United States were taken away one after another.

The earliest telescope

The earliest telescope in the world was made by Italian scientist Galileo in 1609. Therefore, it is also called galileo telescope. This is a refracting telescope. He used a convex crop mirror and a concave mirror as eyepieces, so he observed a positive image. When talking about the world's first telescope, Galileo said: "Now thanks to the telescope, we have been able to make the celestial body thirty or forty times closer to us than Aristotle, so we can distinguish many things that Aristotle did not see on the celestial body; If nothing else, he will never see these sunspots in the solar system. Therefore, we should be more sure about celestial bodies and the sun than Aristotle. "

[Edit this paragraph] English abbreviations related to telescopes

The models of English letters sometimes have different meanings in different telescope brands. Generally speaking, the following contents are easy to identify:

(1) CF: central focus

(2) ZCF: a traditional Poirot prism with left-right expansion and central focusing.

(3) ZWCF: one more "super wide angle" (W) than item (2)

(4) CR: Camouflaged rubber shell

(5) BR: black rubber shock-proof shell

(6) BCF: black, central focus

(7) BCR: black camouflage rubber shell

(8) Infrared: light aluminum shell

(9) IF: Focus the left and right eyes respectively.

(10) WP: nitrogen-filled waterproof type.

(1 1) RA: with rubber shock protection.

(12) D: German prism, roof prism (straight cylinder)

(13) HP: high eye point

(14) SP: ultra-high resolution

(15) ED: ultra-low chromatic aberration lens

(16) AS: aspheric lens

(17) Zoom: A zoom lens with variable magnification.

(18) WF: wide-angle view.

[Edit this paragraph] How to choose a telescope?

At present, there are many kinds of telescopes sold in the domestic market, which is dizzying. But in general, it can be divided into the following aspects: according to different producing areas, there are foreign countries (Japan, the United States, Germany, etc. ) and domestic (Guangdong, Zhejiang, Sichuan, etc. ); According to different brands, there are Xianlifu, Baolong, Debao, Sakura, Kengo, Golden Triangle and so on. , according to different uses, zoom lens, waterproof lens, night vision goggles; According to different magnifications, there are low magnifications (2-5 times, more common in toy products), medium magnifications (7- 10 times) and high magnifications (15-70 times).

When people buy binoculars, there are often several Arabic numerals on the price list. So what technical parameters do these figures explain? Give an example in the next interview. For example, it is marked with 10× 50 mm5, indicating that the magnification is 10, the diameter of the objective lens is 50 mm, and the field of view is 5 degrees (that is, the field of view at 1000 is 87.4m). Some people may think that the greater the number of technical parameters, the better, but it is not. Magnification is inversely proportional to the width of the field of view, that is, the larger the magnification, the smaller the width of the field of view, which is not conducive to search. The larger the diameter of the objective lens and the light input, the stronger the resolution when the light is insufficient, but this will inevitably lead to an increase in the size of the telescope, which is not conducive to carrying. Speaking of this, you may feel at a loss, but as long as you can learn from each other's strengths, you can also buy a telescope that is satisfactory. Here I give you some suggestions for your reference when purchasing telescopes:

First, if you want to travel at sea or by the sea, please don't forget to buy a waterproof telescope (debao offshore series 7×50mm waterproof telescope made in America is especially recommended).

Second, if you want to go sightseeing, you can buy a small telescope with zoom function.

Third, if you plan to hunt in dangerous areas that you can see from a distance but can't explore at close range, buy a high-powered telescope.

Fourth, if you want to hunt or travel for a long time, you'd better buy a zoom telescope. Now explain its usage. Because the zoom telescope can be gradually adjusted from low magnification to high magnification, it should be roughly searched with low magnification and large field of view before carefully observed with high magnification and small field of view.

[Edit this paragraph] Maintenance of the telescope

1. Ensure that the telescope is stored in a ventilated, dry and clean place to prevent mildew. If possible, put desiccant around the telescope and change it frequently.

2. The residual dirty spots or stains on the lens should be gently wiped with professional mirror cloth to avoid scratching the mirror surface. If it is necessary to clean the mirror surface, dip a little alcohol with absorbent cotton, wipe it from the center of the mirror surface to the edge of the mirror surface in one direction, and constantly replace the absorbent cotton ball until it is clean.

Telescope is a kind of precision instrument. Don't slam, weigh or do other violent actions on the telescope.

4. Non-professionals should not try to disassemble the telescope by themselves and clean the inside of the telescope.

High end telescope