Six factors affecting telescope performance
Owning a telescope with excellent performance is the wish of every travel enthusiast. At present, there is a wide variety of telescopes on the market, and the quality is uneven, and there are few articles about telescope knowledge, which makes many people feel unable to start.
Regarding the magnification: the main parameters are marked on each telescope. For example, 7x35 means that the mirror is 7 times and the objective lens diameter is 35mm. Generally, 6 times or less is low magnification, 6-10 times is medium magnification, and 10 times or more is high magnification. Many people always think that the higher the multiplier, the better. Some manufacturers also use false high magnifications to attract consumers. In fact, the reasonable multiplier of a telescope is related to the telescope's aperture and observation method: the larger the aperture, the higher the multiplier can be. , The fixed observation with a tripod can be higher than the handheld observation. If you buy hand-held observation binoculars, the range of 7-10 times is sufficient, and the maximum should not exceed 12 times. Otherwise, the higher the multiple, the smaller and darker the observation field will be, and the observation effect will decrease, especially when it is brought by high magnification. The jitter is also greatly increased, making the observed scene unable to stabilize and difficult to observe normally. Although many countries in the world, such as the United States and Russia, have many types of telescopes equipped with troops, most of them are based on 6-10 times. Some world famous brands such as Zeiss, Nikon and other telescopes also use medium magnification. This is because a clear and stable telescope. The imaging is the most important.
Regarding the caliber: the larger the caliber, the greater the field of view and brightness, which is conducive to observation under dim light, but the larger the caliber, the greater the volume and weight, and the higher the cost. Generally, it can be between 30-50mm according to needs. Optional.
Regarding the field of view: the field of view refers to the field of view observable at a kilometer, such as 1000/93M, which means that the telescope can observe a wide range of 93 meters at a kilometer, and it can also be converted into "degrees" to represent 5 °30'. The comparison of the field of view must be carried out under the conditions of similar aperture and the same multiple. The key to the size of the field of view is the design of the eyepiece part of the prism system. The high-end varieties and military telescopes of general famous manufacturers adopt the wide-angle and large-field design. The large field of view telescope will give people a wide, comfortable and relaxed feeling.
About coating: The function of lens coating is to reduce reflection, increase light transmittance, and improve observation brightness. The color of the coating has nothing to do with the quality. The lighter the coating, the less reflective the better. However, in recent years, various red and yellow film binoculars with strong reflections and brilliance have appeared in the market, which is very attractive to consumers. In fact, this poor quality coating The reflection loses a lot of light, makes the colors colder and darker, and reduces the clarity. What is more, some people call this inferior red film telescope "dimable night vision" and "infrared night vision telescope" to deceive consumers. In fact, the real infrared night vision device is a photomultiplier tube imaging, which is completely different from the principle of a telescope. It cannot be used during the day, is expensive and requires a power supply to work.
Structural materials: In order to reduce costs, most ordinary telescopes on the market use plastic lens bodies and barrels. Only a few advanced products and military models use all-metal structures, which are expensive, but their durability is incomparable. Although the appearance of Soviet-made all-metal military telescopes decades ago is very old, all parts are still flexible in operation and excellent in optical performance.
Military range-finding telescopes are equipped with a dense line for range-finding in the right eyepiece, and the distance between targets can be roughly measured by calculation. But for tourism and sightseeing, the dense line is a bit in the way. Moreover, the distance-finder telescope uses the left and right eyepieces to focus separately, which is a bit more troublesome, so if you don't need it, you don't need to buy a distance-finder.
Some so-called "autofocus telescopes" actually fix the focus at a distance of tens of meters, and use a limited depth of field to achieve a certain degree of clarity, thus eliminating the need for inferior telescopes that reduce the cost of the focusing mechanism. The author has not seen the real Automatic focusing telescope.
What the telescope can see: This is mainly related to the performance of the telescope, the weather conditions, and the size of the target. According to the author’s test: With the Russian 8*40 civilian binoculars, you can see the insects and the number of poles at a distance of 100 meters when the weather is fine. The face of a person a hundred meters away, and vehicles traveling tens of kilometers, you can also see dense craters on the moon, four moons of Jupiter, star clusters and nebulae at night. Friends who are interested in astronomy can give it a try. In fact, one The fun and use of a refractor telescopes is often beyond your imagination.
Some advertisements claim that a certain telescope can clearly see a target one meter away from dozens of hundreds of kilometers away. In fact, theoretically speaking, due to the dense atmosphere near the ground and a lot of dust, and more importantly, the earth is curved, it is impossible. A target one meter away from fifty kilometers away was observed horizontally on the ground.
Purchase: Generally speaking, the world-famous brand binoculars are amazing in terms of optical performance, appearance and feel, and packaging. Of course, the price is not cheap. A famous brand 7x50 binoculars is more than one or two thousand yuan. The optical quality of domestic military telescopes is also good, the price is about 1,000 yuan, but it is basically not seen in the market. In addition, the quality of domestic famous-brand civilian telescopes is also acceptable, and the price is more than two to three hundred yuan, which is acceptable to most people.