Choosing a satisfactory telescope is a very important issue for users, because it determines whether the telescope can meet their personal needs. But beginners often do not have the identification of telescopes and related optical knowledge, especially the current market is full of a large number of inferior telescopes in the reality of the situation, how should beginners buy telescopes?

In view of these confused friends, the author combined their own years of telescope production, sales experience and understanding of the domestic telescope market, organized this article, hoping to be helpful to everyone, especially rookie friends:

 

1. Determine the optical system structure and magnification range of the telescope according to its own use

The ultimate goal of buying a telescope is to be comfortable to use, so determining the main purpose is crucial and is the first step in the purchase, which determines the next steps. It can be imagined that if the main purpose is to watch sports games, then the purchase of PCF structure of the large telescope, the actual use will feel heavy and stupid, can not lift for a long time the wrist is sour, where there is a good mood to watch the game.

In addition, the magnification is not the bigger the better, because it magnifies not only your field of view Angle, but also the shaking of your hands, generally speaking, the most suitable magnification for human eyes on land is 6-12 times, and 6-8 times the best, more than 12 times later due to the field of view Angle and the small diameter of the entrance eye, the shaking of the hand is also multiplied. Hand-held observations are more difficult. This is why most military telescopes are in this magnification range (some sea telescopes have magnifications of 15 to 20 times).

 

2. Pay attention to the difference between nominal parameters and real parameters

You may notice that telescopes generally have at least two parameters like this printed on them: 8X21 131M/1000M, (the latter or printed as a parameter like 393FT/1000YDS, sometimes also printed as a parameter like FILE=7º, but this printing is less common), this is the most critical parameters of a telescope, the former represents the telescope's magnmagnity and light aperture, For example, 8X21 represents the magnification of 8 times, the light aperture is 21mm, and so on, if the printed parameter is 10X50, it represents the magnification of 10 times, and the light aperture is 50mm. So knowing the meaning of this parameter, it is easy for us to determine whether the parameters printed by a telescope are real, for ordinary fixed magnification telescopes commonly on the market, if the magnification is too high, we should be skeptical, and it is necessary to carefully evaluate whether it is real in combination with other parameters (magnification telescopes can reach 15 times, 20 times, 30 times or higher magnification). Such as common 7-15X35, 8-24X50, 10-30X60 and other specifications). The determination of light aperture is relatively simple, generally speaking, it is approximately equivalent to the telescope's objective diameter (in fact, it is 1-2mm smaller, but negligible), such as clearly the telescope's objective diameter is only 20mm, that is, about 2 cm, the telescope is marked as similar to 980x30, 20x50 or even larger parameters, Then it must be a false multiplier no doubt.

Another parameter, that is, similar to 131M/1000M such a parameter, it represents the telescope's field of view Angle, the principle is more complex, and another article describes, here gives the common telescope field of view Angle, different manufacturers of products may be slightly different, but little change, If you see an exaggerated parameter such as 9999M/10000M printed on a telescope, then it must be a (private small workshop) workshop work.

Common telescope models corresponding field of view Angle (this parameter is for reference only, different manufacturers may vary slightly) :

8x21 131m/1000m

10x25 96m/1000m

12x25 80m/1000m

7x35 147m/1000m

7x50 147m/1000m

10x50 122m/1000m

12x50 97m/1000m

 

Third, whether the appearance is beautiful and fine, whether the structural design is reasonable, whether the rotation part of the mechanism is flexible and comfortable, and whether the assembly quality (especially the focusing of the optical axis) is passed.

Regular telescope factory appearance requirements are very high, and from the raw materials and assembly of all aspects of the factors affecting the appearance of the control, the purchase of telescopes should pay attention to whether the appearance is beautiful and fine, such as whether the veneer is smooth, whether the trim is neat (street works generally use poor quality veneer, the use of manual trimming method, limited by the technical level of workers and equipment, The skin is not smooth, uneven and other shortcomings), whether there is damping grease residue and leakage on the outer surface of the telescope, on this basis, pay attention to whether the structural design is reasonable, such as the position of the focusing hand wheel is reasonable, whether the feel is flexible, smooth and comfortable, and whether the visibility compensation of the eyepiece part (generally the right eyepiece) is flexible.

In addition, special attention should be paid to whether the optical axis of the telescope is accurate, the optical axis parallelism of the regular telescope left and right mirror tube is corrected to a certain Angle by special instruments before the factory (divergence ≤35 ', convergence ≤60 '), when the parallelism of the optical axis exceeds this range, it is called the optical axis aberration, which will be judged as seriously unqualified products in the regular factory. The use of the telescope with abnormal optical axis will cause dizziness, eye pain and other adverse reactions, and long-term use will cause serious damage to vision. Therefore, the adjustment of the optical axis is very strictly controlled in the regular factory, and the workers responsible for the adjustment are also the best workers selected from the assembly workers after a long time of special training, and the adjustment of a telescope is also a longer time. On the one hand, the works on the street are limited by the quality of the products (poor quality components, assembly quality and other factors may determine that it is difficult to adjust such telescopes to the standard optical axis), by the equipment (the price of the comparator is high, and a lot of equipment is required due to low productivity), and on the other hand, because in order to increase production, Reduce costs (because poor quality telescopes are not worth the cost if they are adjusted in accordance with the formal adjustment method), use lower inspection standards, and even subjective adjustment methods (The author has seen a factory using adjustment workers facing a white wall adjustment, not equipped with any instruments, The quality of the product is not guaranteed only according to whether the worker feels dizzy subjectively.

 

Fourth, whether the optical components are genuine optical components

The telescope market is uneven, the development of telescope materials is also changing with each new day, before 2000, inferior telescope manufacturers basically used waste defective optical components, and after 2001, there was a new resin lens, the cost is cheaper (it is reported that 0.2 yuan /PCS, the price of normal eyepiece lenses, Even the lowest price of the most common small-size DCF telescopes is 4-5 yuan /PCS), and the optical performance is further reduced.

In the prism section of the identification method of optical components, due to the large volume of the telescope prism, it is difficult to use resin to manufacture, so basically the method of shoplifting is still used. It is also relatively easy to identify, invert the telescope, look from the end of the objective lens to a bright open place, if there is a black broken line inside (relative to the DCF telescope with a ridge prism), or there is a black stain, then this indicates that the telescope is assembled with waste products, black broken lines and black spots are actually broken ridges and broken points of the prism.

Look closely at the eyepiece of the telescope, if it is not light blue but white (actually colorless), indicating that the eyepiece is not coated, why is it not coated? Because it is pressed with plastic resin, it is put in the coating machine before the coating is started during the preheating stage of the coating material is baked and deformed or melted.

However, the eyepiece system of the general telescope has several lenses, and some works use the outermost lens with optical elements, and the inner lens with resin lenses. Heheh! The devil is a foot high, and the road is a foot high. The original resin lens has a congenital deficiency, that is, the quality is not good, especially the color difference and distortion are extremely serious, may wish to pick up the telescope to look at the distant rod object, it is best to be light colored, such as a telephone pole, if you find that the edge of the image of the telephone pole is covered with a rainbow coat, and the edge of the telescope field of view is very fuzzy, it is a fake.

 

Five, whether the accessories are complete,

Any retail optical telescope generally contains the following accessories: lanyard, mirror cloth, desiccant, mirror bag, a packaging box. If these basic configurations are not complete, then it is likely that corners are cut in order to reduce costs, especially PCF telescopes, and workshop works are generally not suitable for packaging color boxes. There are also some bad vendors, under the banner of 10 yuan to send backpacks to customers to kill a knife, the telescope's original leather bag sold to customers again.

 

Resist the temptation of low prices, carefully buy products, and pay attention to whether the performance is consistent with the description

In 1997, an 8X21 DCF telescope, the lowest market price is more than 300 yuan. At present, the lowest price on the market can be more than 10 yuan. Price war is really a trial-and-true weapon in the community, and often some friends are deceived by unscrupulous vendors' low prices and dark lies. It was cheap, but I got a bunch of junk. For example, the market is now common in all kinds of colorful "military telescopes" and "Russian telescopes", the general vendors ask for more than 200 yuan to 80 yuan, is it really cheap? Such products in the voluntary wholesale market only sell more than 20 yuan, and the ability to compress the cost in the street can really play to the extreme, that is, the price of optical wool glass purchased in accordance with the kilogram, and this price is not enough to buy and process such a telescope optical wool glass. So how did this telescope come about? It's simple. Plastic and a little window glass. Therefore, user friends must carefully judge when purchasing telescopes according to the above principles, pay attention to whether the performance of the product is consistent with the description, and do not listen too much to the word of the small trader, so as not to be deceived.

 

The author believes that as long as we grasp the above principles, under normal circumstances, we will be able to buy a satisfactory telescope.

 

This article is spent two nights to sort out, due to their own limited level and time rush, the inadequacies are inevitable, welcome to criticize and correct. At the same time, please also appreciate the author's hard work, reprint is as far as possible to indicate the original author and source, I would like to express my sincere thanks.