Infrared ray is one of the many invisible rays in the sun's rays, which was discovered by German scientist Huxley in 1800. Also called infrared thermal radiation. He used a prism to decompose sunlight, and placed thermometers at the positions of various colored bands, trying to measure the thermal effects of various colors of light. The thermometer located outside the red light has the fastest temperature rise. Therefore, it is concluded that there must be invisible light, that is, infrared light, besides red light in the solar spectrum. It can also be used as a transmission medium. In the solar spectrum, the wavelength of infrared light is greater than that of visible light, and the wavelength is 0.75 ~ 1000 micron ... The infrared light can be divided into three parts, namely the near infrared light with the wavelength of 0.75 ~ 1.50μ m; Mid-infrared, the wavelength is between 1.50 ~ 6.0μ m; Far infrared ray, whose wavelength is between 6.0 ~ 1000 μ m, is an electromagnetic wave whose wavelength is between microwave and visible light, and whose wavelength is between 770nm ~ 1mm, which is outside the red light in the spectrum. It has a strong thermal effect and is easily absorbed by objects, and is usually used as a heat source. The ability to penetrate clouds is stronger than visible light. It is widely used in communication, detection, medical treatment and military fields. Commonly known as infrared light. The real infrared night vision instrument is photomultiplier tube imaging, which is completely different from the principle of telescope. It can't be used in the daytime, it is expensive and needs power to work.
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Multiplication:
Each telescope is marked with main parameters, such as 7×35, which means that the mirror surface is 7 times and the objective lens is 35mm. Generally, below 6 times is low power, 6- 10 times is medium power, and above 10 times is high power. Many people always think that the higher the multiple, the better. Some manufacturers also use false high magnification to attract consumers. In fact, the reasonable magnification of the telescope is related to the aperture and observation mode of the telescope: the larger the aperture, the higher the magnification, and the fixed observation with tripod can be higher than the handheld observation. If you buy hand-held binoculars, 7- 10 times is enough, and at most it is not more than 12 times. Otherwise, the higher the magnification, the smaller and darker the observation field of view will be, and the observation effect will be reduced, especially the jitter caused by high magnification will be greatly increased, making the observed scenery unstable and difficult to observe normally. Although there are many kinds of telescopes in the world, including American and Russian, most of them are 6- 10 times. Some world-famous brands such as Zeiss and Nikon also produce telescopes with medium magnification, because clear and stable imaging is the most important.
Caliber:
The larger the aperture, the greater the viewing field and brightness, which is conducive to observation in dim light. However, the larger the aperture, the larger the volume and the higher the cost. Generally, it can be selected between 30-50mm as needed.
Vision:
The field of view refers to the observable field of view at a kilometer, such as 1000/93m, which means that the telescope can observe a range of 93m wide at a kilometer, and it can also be converted into "degrees" and expressed as 5 30'. The comparison of the size of the field of view must be carried out under the condition of similar caliber and the same multiple. The key to the size of the field of view lies in the design of the eyepiece part of the prism system. General famous factories and advanced varieties of military telescopes all adopt wide-angle and large-field design, which will give people a feeling of being broad, comfortable and relaxed.
Coating:
The function of lens coating is to reduce reflection, increase transmittance and improve observation brightness. Different coating colors have nothing to do with quality. The lighter the coating, the smaller the reflection, the better. But in recent years, all kinds of red and yellow telescopes with strong reflectivity have appeared in various markets, which are very attractive to consumers. Is this kind of telescope with red and bright objective a night vision telescope? This explanation is "infrared, sub-infrared, ruby coating, gold coating, all-weather night vision telescope" and so on. In fact, when light penetrates the glass, it will inevitably cause some reflection and reduce the brightness. After the red film is coated, the brightness will be reduced even more because of the serious reflection. This kind of telescope is usually used to reduce the brightness when the sunlight is strong and dazzling in the snow. This coating reflection loses a lot of light, making the color colder and darker, and the clarity decreases. What's more, some people even call this kind of red film telescope "night vision" and "infrared night vision telescope" to deceive consumers. In fact, it's true.
Materials:
In order to reduce the cost, most ordinary telescopes on the market use plastic lens barrels, and only a few advanced products and military models use all-metal structures, which are expensive, but their durability is unparalleled. The military ranging telescope is equipped with dense bit lines in the right eyepiece for ranging, and the distance between targets can be roughly determined by calculation. However, for sightseeing, the secret passage line is a bit remote. Moreover, the ranging telescope is a bit troublesome because the left and right eyepieces are focused separately. Unless it is particularly necessary, it is not necessary to choose a ranging telescope. Some so-called "autofocus telescopes" actually fix the focus at tens of meters away and use the limited depth of field to achieve certain clarity, thus canceling the focusing mechanism and reducing the cost. At present, no real autofocus telescope has been seen.
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This is mainly related to the performance of the telescope, weather conditions and target size. When the weather is fine, the 8×40 civil binoculars can clearly see the bugs on the telephone poles 100 meters away, the faces of outsiders hundreds of meters away, and the vehicles driving dozens of kilometers away. At night, you can also see the dense craters on the moon, four satellites of Jupiter, cluster nebulae and so on. Friends who are interested in astronomy can try it. In fact, an excellent telescope will often bring you more fun and uses than you.
Edit this paragraph to distinguish between true and false.
In recent years, a large number of plastic shells, camouflage, gray and other colors have appeared in various markets, using ordinary lenses and prisms, plating red films, green films and yellow films, and designing with a small field of view. Some have compasses and coordinate lines, and the mirror body is printed with Russian, Russian * * * party emblem, cannon red star and so on. Marked dozens or even thousands of times, it claims to be able to see the "twilight" of dozens or hundreds of kilometers. The real Russian telescope can only be seen in the border trade zone, and there are not many deliveries. Russian telescope is characterized by its traditional appearance, solid and durable all-metal structure (a small amount of engineering plastics is used for civil use to reduce the cost), serial number engraved on the mirror body, high-quality composite achromatic optical lens, high-quality light blue, light purple and light yellow antireflection film, K4 advanced prism material, wide-angle and wide-field design, real magnification and excellent optical quality, which fully embodies the superb optical level of the former Soviet Union.
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Take several binoculars with the same magnification, the same caliber and different brands, pick up the binoculars, face the bright place, about 30 cm away from the eyes, and you can see two bright circles, called the exit pupil. If the exit pupil of these binoculars is the same, the magnification is the same; if they are different, there is something wrong with the magnification. The larger the magnification, the smaller the bright circle will be, so for a telescope like 10×50, the circle at the eyepiece must be much smaller than a telescope like 7×50. This is because the exit pupil diameter = aperture/magnification. Reminder: When comparing telescopes, be sure to compare them with telescopes with the same magnification.
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According to personal preference and usage, it is more practical to buy a telescope between 7 times and 12 times. If it is used for reconnaissance or navigation, it is ideal to buy a 20×60 or 30×60 telescope, but it needs to be fixed with a tripod.