There are a variety of binoculars on the market. Their appearance, size, price, and use are different. Some are used for viewing scenery, sports competitions, theatrical performances, some are used to observe birds and other animals, and some are used to For fixed-point surveillance (such as forests, electricity, public security, etc.), there are also people who appreciate the magical and beautiful objects in the night sky... If you want to buy a binocular suitable for you, you must know the following knowledge:
What does the number in the telescope model mean?
Binoculars sold on the market are marked with such numbers as "7 ́35", "8 ́50", "15 ́70", etc. The numbers in front of the " ́" symbol represent the magnification (the above three telescopes The magnifications are 7, 8, and 15), and the numbers behind the “ ́” symbol represent the diameter of a single objective (mirror close to the observer) of the binoculars in millimeters (the calibers of the three telescope objectives are respectively 35, 50, 70mm). Analogous numbers appearing in the telescope model also have the same meaning. For example, the models of the above three telescopes have the numbers “0735”, “0850”, and “1570”. There are also some high-end zoom telescopes, their magnification can be continuously changed within a certain range, such as "082450" means that its magnification can be continuously changed from 8 times to 24 times, the objective lens diameter is 50mm; "206078" means that its magnification can be continuously changed from 20 times to 60 times, and the objective lens diameter is 78mm...
Magnification (magnification) and field of view
The telescope's magnification (magnification) is the magnification of the target's angle of view when viewed through the telescope (informally, the ability of the telescope to zoom in on an object. For example, using a 7x telescope to observe an object at 700 meters is equivalent to using Visual observation of an object at a distance of 100 meters. Its value is equal to the ratio of the focal length of the objective lens to the focal length of the eyepiece. In the case where the focal length of the objective lens has been fixed, changing the focal length of the eyepiece can change the magnification of the telescope. The field of view is the size of the range that can be seen through the telescope. The larger the field of view, the wider the scope of observation and the more comfortable it is to feel. The field of view is usually measured in kilometers (observable width in meters) or converted into angles. The size of the field of view is inversely proportional to the magnification. The larger the magnification, the smaller the field of view.
Is the magnification bigger?
Most people believe that the higher the magnification of the telescope, the better the effect seen, but the fact is the opposite. In the case of the same objective lens diameter, the higher the magnification, the poorer the imaging quality, the more blurred the landscape seen. . If you are using a telescope to view scenery, performances, competitions, etc., it is generally best to use a magnification of 7 to 8 times, because if you look at this low magnification lens, the image will be brighter and more stable, and the field of view will be larger; if If you use 10x or more high magnification observations, you will find that it seems to be getting bigger, but the field of view is getting smaller (if you see the stadium can only see a corner, you can see the stage only see a few actors...). As the image is darkened, the stability becomes worse (dithering is aggravated). Since it is difficult for most people to hold a 10x or more binoculars with their hands for a long time, in practice, you will find it difficult to find a telescope. Find the goal. Most military telescopes in the world are mainly 6 to 10 times. China's military telescopes are mainly 7 and 8 times. It is because clear and stable imaging is very important.
Some dealers are notorious, boasting that their telescopes can magnify dozens or hundreds of times, attracting and deceiving customers with false high rates, and many consumers are deceived. For example, if you don't have a large enough aperture to ensure that the magnification is like a photographic film that doesn't have a high enough resolution guarantee, if their binoculars really can be magnified hundreds of times, then the scene you see will look like a picture. Ordinary film is enlarged to a large stadium. Can you still see clearly? ! I believe that the friend who read this article will never believe the ghosts again.
If you need to observe the details and close-ups of some small-scale scenes (such as bird watching, animals, observing celestial bodies, etc.) or you need to take photos, etc., you must use 10 times more telescopes (in order to clear the image, the aperture must be increased accordingly). , but at this time you must have a solid tripod for binoculars.
Can't see clearly what is the main factor?
The larger the aperture of the telescope (which is roughly equivalent to the diameter of the objective lens), the stronger the ability to collect light and the clearer the image (the more professionally referred to as “resolution” or “resolve power”), The size of the telescope aperture limits the magnification it allows, so if you want to see more clearly, not to increase the magnification, but to increase the aperture. However, for hand-held binoculars, the increase in the aperture of the objective lens will make the telescope bulky, so the diameter of the handheld binoculars should not exceed 60mm, otherwise it can not be stabilized without a tripod. If you are using binoculars often in bright places. It doesn't matter much if the caliber is a bit smaller, but if you want to observe the target in relatively dim light, such as watching a stage with poor lighting, dark animals, or observing celestial bodies, then the larger calibre is important. It will directly affect whether you can see clearly.
Of course, the objects in the telescope are not clear, and in addition to the caliber of light, it is also related to many other factors, such as the materials, shapes, structures, grinding, glueing, coating, installation, and debugging of the lenses, as well as the type and quality of the eyepieces. Therefore, even telescopes with the same calibre can cause great differences in imaging quality due to the above factors. It is often difficult for outsiders to understand and identify these telescopes.
In general, you should choose the caliber, weight, size, quality, price, etc. for your binoculars according to your purpose of use, use of the environment, and economic conditions.