Telescopes are a must-have equipment for outdoor sports enthusiasts, so do you know how to buy outdoor telescopes? Below, I will introduce you to the guide to purchasing and using outdoor telescopes.

How to choose outdoor telescopes

1. PANDA (one of the earliest telescope brands in my country, started in 1936, one of the top ten telescope brands)

2 , Bosma (the only designated telescope brand in the F1 China Division (Shanghai), one of the top ten telescope brands)

3. Tianlang (the popular science astronomical telescope has always ranked first in sales in the country, one of the top ten telescope brands)

4. Phenix (Phoenix Optical Group Co., Ltd., China’s well-known trademark, Chinese famous brand)

5. Canon (1937 Japan, Canon (China) Co., Ltd., top ten Telescope brand)

6. Steiner (founded in Germany in 1947, a famous international, top ten telescope brand)

7. Nikon (founded in 1917 in Japan, Nikon ( China) Co., Ltd., top ten telescope brands)

8. LEICA (Germany in 1849, the world leader in optical manufacturing, top ten telescope brands)

9. Xiguang Telescope (Xiguang Group was founded in 1953, a high-tech national defense optoelectronic enterprise)

10. VISIONKING (VISIONKING was established in 1999, leading the industry at home and abroad) Ranking of the world's top ten telescope brands

1. Cat PANDA (one of the earliest telescope brands in my country, one of the scientific research and production bases for night vision products in the national defense industry, a famous brand, Yunnan North Optoelectronic Instrument Co., Ltd.)

2. Bosma (Professional astronomical telescope/binoculars and other series of optoelectronic instrument product manufacturers, Guangzhou famous trademark, Guangzhou Boguan Optoelectronic Technology Co., Ltd.)

3. Zeiss ZEISS (founded in 1846 in Germany, one of the top ten telescopes Brand, one of the world's leading optical instrument manufacturing companies, Carl Zeiss Optics (China) Co., Ltd.)

4. Canon (founded in Japan in 1937, the world's leading comprehensive manufacturer of imaging and information products Group, Fortune Global 500 company, Canon (China) Co., Ltd.)

5. Nikon (Japan in 1917, a world-famous optical product designer and manufacturer, industry-leading brand, Nikon imaging instrument sales (China) Co., Ltd.)

6. Steiner (In 1947, the world's largest manufacturer of military telescopes and one of the largest and most modern lens production equipment companies, German Steiner Optical Company)

7. Leica (founded in 1907, one of the world’s leaders in optical manufacturing, with a history of 160 years of microscope manufacturing, one of the top ten telescope brands, Leica Camera AG)

8 , Xiguang (affiliated to China Ordnance Industry Group Corporation, a state-controlled listed company, one of the domestic optical glass material production bases, Northern Optoelectronics Co., Ltd.)

9. Tianlang Tianlang (committed to the research and development of astronomical instruments and equipment , manufacturing, sales and astronomical science popularization guidance professional group enterprise, Beijing Sirius Deep Space Optoelectronics Technology Co., Ltd.)

10. NIKULA (China's major telescope exporter integrating product research, development and manufacturing, Top ten telescope brands, Foshan Nanhai Weihong Mold Manufacturing Co., Ltd.) Guide to purchasing and using outdoor telescopes

1. The meaning of the mirror body mark

Take the BAIGISH10X40 telescope mirror as an example: The left mirror shoulder has the words "10 The diameter of the objective lens is 40 mm. The larger the diameter of the objective lens, the brighter the image, but the portability will decrease.

There are also the words "114M/1000M" on the shoulder of the left mirror, which means that at a distance of 1000 meters, the range that can be seen through this telescope is a circle with a diameter of 114 meters. This actually represents the concept of a field of view. Conversion The angle is 6.5 degrees

Some telescopes use xx ft at 1000yds to express the size of the field of view, where ft represents feet and yds represents yards, both of which are imperial units. Taking the Zeiss 7x50 B/GA telescope as an example, its field of view is 390ft at 1000yds

2. BAK4 and BK7 materials

BAK4 and BK7 are the numbers of two different materials of optical glass . The refractive index of these two types of glass is different. BAK4 has a high refractive index. For the porro prism made of BAK4, it can completely reflect 100% of the incident light without considering absorption, while BK7 can only reflect about 83% of the incident light. Therefore, BAK4 has high light efficiency, but it is also expensive. Military telescopes and some high-quality civilian mirrors use BAK4 prisms. The easiest way to determine the material of a prism is to look at the shape of the exit pupil behind the eyepiece.

For roof prisms, because of their special structure, there is no difference between the two materials. The prism material cannot be distinguished from the shape of the exit pupil. Many roof prism telescopes also claim that they use BAK4 material prism, this is basically for commercial considerations and technically makes no sense.

3. The significance of lens coating

When light shines on the surface of the lens, part of the light will be reflected. A typical telescope has more than 10 reflective surfaces. Even if each reflection The surface of the telescope only reflects a few percent of the light. In addition to the absorption of light inside the lens, more than 50% of the light that finally enters the eye may be lost. Not only is the image dim, but the reflected light is reflected multiple times inside the telescope, and part of it enters the eye through the eyepiece. It forms glare, interferes with observation, and also reduces the contrast of imaging.

When a 1/4 wavelength film is coated on the surface of the lens, the transmittance of light of this wavelength can be increased. The more common blue film is the simplest anti-reflection coating. High-end mirrors will use multi-layer films that can increase the transmittance of the entire visible light band.

There are many red-coated telescopes on the market. This kind of mirror is generally only suitable for highly reflective environments such as snow. Daily use will cause problems such as dark images and serious color casts. In addition, in order to reduce costs, some mirrors only coat part of the lens (usually the outer surface of the objective lens and eyepiece). A good mirror will coat all lens surfaces, and a better mirror will coat some lenses with multiple layers of film. , the best mirrors will have multiple layers of coating on all lens surfaces. The easiest way to judge the quality of a mirror's coating is to observe the reflection of the lens. The darker the reflection, the more transparent the lens, and the better the coating.

　4. Nitrogen-filled waterproof and all-metal structure

Many telescopes will highlight the characteristics of nitrogen-filled and waterproof, because this is a typical feature of high-quality telescopes. It means that water vapor and dust cannot enter the interior of the telescope. With the protection of dry nitrogen, the internal lenses will not fog up or grow mold, ensuring the telescope has a long service life and is also suitable for extremely harsh environments. Therefore, general military telescopes, such as the Type 95, are designed to be nitrogen-filled and waterproof. Some civilian mirrors also adopt this design. Don't think that this is a very expensive measure. The 6X18, which only costs more than 100 yuan, also adopts this design.

It should also be emphasized that this design does not directly bring optical improvements, the only improvement is durability. At present, Russian telescopes and domestic regular military telescopes are all metal structures (usually aluminum, old military telescopes often use brass). The advantage of this structure is that it is very durable, without the disadvantages of plastic that will slowly age and be easily deformed. Although it cannot directly bring optical progress, it can ensure that optical parts are always in a precise position, thereby bringing long-term optical stability.

Because of the high cost of metal structures, only military telescopes and high-end civilian mirrors use this structure, while ordinary civilian telescopes often use a mixed structure of metal and plastic

　5. Porro and roo prisms

The image seen through a typical Kepler telescope is upside down, left and right. In order to meet the needs of ground observation, a set of prisms must be added behind the objective lens (which turns the distant target into an inverted real image). The inverted real image is transformed into an upright real image. There are two structures of prisms to achieve image rotation, porro prism and roof prism.

The advantages of the porro prism are simple structure, high light transmittance and good imaging quality, but the telescope is relatively large.

In order to overcome this shortcoming, reverse porro prism image conversion can be used, but it brings new problems. The diameter of the objective lens is too small and is not suitable for use in low-light environments.

The biggest advantage of the roof prism is that after using it, the size of the telescope can be minimized and the weight of the telescope is also reduced. However, the structure of this prism is complex, and the light transmittance is 5% lower than that of the porro prism. It needs to be coated with phase coating, so to make a high-quality roof prism telescope, you need to pay a lot of money.

6. Exit pupil diameter and exit pupil distance

The exit pupil diameter is the size of the spot formed by the image passing through the telescope behind the eyepiece.

This is also an important indicator of the telescope. It represents the imaging brightness that the telescope can achieve. Generally speaking, telescopes with exit pupils between 2.5 mm and 4 mm are more suitable for solar imaging. For daily use, telescopes between 4 mm and 7 mm can still be observed in daytime and low-light environments, while telescopes below 2.5 mm have very low image brightness even during the day, and are difficult to align with the pupil of the human eye, making observation comfortable. Sex sucks. The simple formula for calculating the exit pupil is objective lens diameter/magnification = exit pupil diameter. For example, for a 7X50 telescope, the exit pupil diameter = 50/7 = 7.14 mm. The exit pupil distance refers to the farthest distance between the eye and the eyepiece when the entire field of view can be seen clearly.