How to choose the coating of the telescope? How to remove that coating of the telescope

Here's a little bit of knowledge about optical glass coating:

coated optics

It is the lowest level of anti-reflection coating. It simply means that at least one optical surface is coated with a single layer of anti-reflection coating, usually on the outer surface of both objectives and eyepieces, while the inner lens and prism are not coated.

Fully Coated All lenses and prisms are coated with a single coating, but if an optical plastic lens is used in the eyepiece, the plastic lens may not be coated.

multi-coated

At least one optical surface is coated with multiple layers of anti-reflection coating, and other optical surfaces may be coated with a single layer of film or no coating at all; Typically, only the outer surface of the two objectives and eyepieces is coated with multiple films.

Fully multi-coated: All lenses and prisms are coated with anti-reflection coatings, some manufacturers have multi-layer coatings on all optical surfaces, while others only have multi-layer coatings on some optical surfaces, and the other surfaces are still coated with a single coating.

In China, there are broadband green film, decorative green film, red film and blue film, as well as purple film and yellow film

1. Broadband green film: some places also call anti-reflection green film, which is currently one of the best coatings in China, which will present different color bands at different angles (this is the performance of multi-layer coating), good imaging and high definition, and good color reproduction.

2. Red film: Generally only used on red dots, this is more versatile and has no characteristics.

3. Blue film: It is the most widely used coating method in China, compared with the broadband green film, it is slightly yellow and dark, and the blue film is also layered, some are plated with three layers, some are better with five layers, and the poor one is only one layer.

4. Decorative green film: This is very lacking in morality, the color is very similar to the anti-reflection green film, but the optical performance is not flattering, and the easier way to identify is that the decorative green film is very reflective, and the broadband green film is very light.

If you have other questions, please feel free to ask, if you are satisfied, I hope it will be helpful to you.

When choosing a coating for a telescope, you can choose according to the following principles:

1.Anti-reflection coating (also known as anti-reflective coating): This film is used to reduce the reflected light from the glass surface of the telescope.

It can make it easier for light to pass through the telescope's lenses, improving the telescope's brightness, clarity, and contrast. Anti-reflection coatings are generally applied on the concave surface of the telescope, and some are applied on the convex surface.

2.Anti-reflective film (also known as anti-glare film): This film reduces glare and ghosting on the surface of the telescope's glass, thereby improving the contrast and clarity of the telescope. Anti-reflective films are generally applied on the convex surface of the telescope, but also on the concave surface.

3.Abrasion resistant film (also known as hard coating): This film can increase the hardness and abrasion resistance of the telescope lens, thereby extending the life of the telescope. Abrasion-resistant films are generally applied on the convex surface of the telescope, but also on the concave surface.

4.Anti-fog film (also known as anti-fog film): This film reduces fog and moisture inside the telescope, which improves the clarity and contrast of the telescope. Anti-fog films are generally applied on the concave surface of the telescope, and some are applied on convex surfaces.

5.High Reflective Coating (also known as High Brightness Film): This film increases the reflectivity of the telescope, thereby increasing the brightness and contrast of the telescope. Highly reflective coatings are generally applied on the convex surface of the telescope, but also on the concave surface.

These are the types of coatings commonly used for telescopes, and the specific coating depends on the telescope's usage needs and optical design. When choosing a telescope, you can consider the above information comprehensively.

It's not as simple as you think. It is not advisable to choose a telescope based on the coating, just keep in mind that you should not choose the red coating that claims to be night vision, or the sparkling yellow coating. The rest is fateful.

Generally, broadband coating is good, but it does not mean that broadband coated telescopes are good, you can understand it when you look here.

This stuff is just some very basic and cannot be used as a basis for detailed judgment.

Fully multi-coated: All lenses and prisms are coated with anti-reflection coatings, some manufacturers have multi-layer coatings on all optical surfaces, while others only have multi-layer coatings on some optical surfaces, and the other surfaces are still coated with a single coating.

In China, there are broadband green film, decorative green film, red film and blue film, as well as purple film and yellow film

1. Broadband green film: In some places, it is also called anti-reflection green film, which is currently one of the best coatings in China.

The coating of the telescope can be removed with a sodium hydroxide solution. The coating of the telescope is a protective film, and sodium hydroxide has a strong corrosive alkali, so it can be removed by applying sodium hydroxide solution.

A telescope is an optical instrument that uses a lens or a mirror and other optical devices to observe distant objects, which uses the light refraction through the lens or the light is reflected by the concave mirror to make it enter the small hole and image, and then be seen through a magnifying eyepiece, also known as a clairvoyant.

The history of the development of telescopes.

The first function of the telescope is to magnify the opening angle of distant objects, so that the human eye can see details with smaller angular distances. The second function of the telescope is to feed the beam of light collected by the objective lens that is much thicker than the diameter of the pupil into the human eye, so that the observer can see faint objects that were not previously visible.

In 1608, Hans Liberch, an optical merchant in the Netherlands, stumbled upon the idea that he could see in the distance with two lenses, and he built the first telephoto mirror in human history. In 1609, Galileo Galilei, a native of Florence, Italy, invented the 40x double-mirror telescope, which was the first practical telescope to be put into scientific applications.

Reasons for telescope lens coating and how to identify quality:

Because when the light shines on the surface of the lens of the telescope, part of the light will be reflected, a typical telescope has more than 10 reflective surfaces, even if each reflecting surface only reflects a few percent of the light, plus the absorption of light inside the lens, the light that finally enters the eye may lose more than 50%, not only the imaging is dim, but also the reflected light is reflected many times inside the telescope, and some of them enter the eye through the eyepiece, forming glare, interfering with the observation, and reducing the contrast of the imaging. When the surface of the lens is coated with a 1 4 wavelength film, the light transmittance of this wavelength light can be improved, the more common blue film is the simplest anti-reflection film, and the more high-end mirror will use a multi-layer film, which can improve the light transmittance of the entire visible light band.

There are many red film telescopes on the market**, which are generally only suitable for highly reflective environments such as snow, and daily use will cause problems such as dull imaging and serious color casting. In addition, in order to reduce the cost, some mirrors are only coated on some lenses (usually the outer surface of the objective lens and eyepiece), good mirrors will be coated on all lens surfaces, better mirrors will be coated with multiple layers on the surface of some lenses, and the best mirrors will be coated with multiple layers 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.

Precautions for purchase:

1) The imaging effect of the telescope depends on many factors, and the magnification is only one of many factors, and it is not advisable to blindly pursue the magnification. The possibility of a fake military telescope is extremely high, and regular military telescopes are basically black and expensive.

2) Do not buy binoculars with a wide range of zoom, there are many problems such as small field of view, serious imaging distortion, and easy deviation of the optical axis. You must know that you get what you pay for, and the actual effect of a telescope with the same specifications and parameters may be very different, of course, it will be thousands of miles apart.

3) Try not to buy a red film telescope, it is only suitable for high reflection environments such as ice and snow, and the imaging in the general environment is dim and the color cast is serious.

4) There are never any infrared night vision telescopes, but some size telescopes, such as 7x50, also work well in low-light environments.

Actually, the question you are asking is not a good question, but a basic dividing line.

Red film, basically without any advantages. In addition to being decorative.

Of course, for some unscrupulous vendors, it can be advertised as "night vision" and "infrared" to deceive consumers - this can be said to be a "plus" for them.

Therefore, regular products rarely use red film, so it can be considered that most of the telescopes that use the shiny mirror-like red film and yellow film are inferior products.

Both blue and broadband coatings are regular anti-reflection coatings. But now there is a kind of "false green film", which is made green by some means, and is used to pass off as a broadband film, which has the same properties as the red film. Nothing good.

Basically, blue film is a traditional optical coating. The real broadband film is also good, and the permeability can be improved by less than 1% compared to the blue film, which seems to be the case in my impression, and the difference is not big.

The best film is actually the one with the darkest reflection.

It should be noted that you can't just look at the film, many inferior products nowadays deliberately use green coating on the obvious part of the product - just like using good paint on the outside of furniture made of broken wood to deceive consumers.

Blindly pursuing the so-called "green film" is easy to be fooled.

In short, comprehensive identification is the most important, that is, do not stare at what coating, but look at the system, now there are a lot of counterfeits, counterfeit and inferior accounted for more than 95% of the market, and there are all kinds of false propaganda, such as "night vision", "infrared", "Japanese cherry blossoms", "Russia" and so on, it is recommended that you understand the basic knowledge of basic identification.

Particular attention is paid to the issues related to multiples, military, night vision, etc., that is, the introduction of some common false propaganda. Basically, there is a more familiar understanding of these aspects, and being careful is the most important thing.

In addition, I would like to add that the hand-held one generally does not choose the zoom one.

First of all: the blue coating is an ordinary single-layer coating, because it is a single-layer coating, there are still some residual reflections, so the reflective color is slightly brighter (compared to multi-layer coatings).

Secondly: due to the multi-layer coating, there is very little residual reflection, and the reflective color is dull. Dark green, dark blue, and purple are multi-layer coatings.

In particular, the dark green coating, known as the "broadband anti-reflection coating", can make the light reflectance in a wide area of the visible spectrum (450 650nm) less than the cost of multi-layer coating, and is mostly used in high-end telescopes.

So: the darker the lens reflection, the better the coating performance, and the stronger the lens reflection, the worse the coating performance.

At present, many shoddy telescopes on the market use a highly reflective red coating for their objective lenses, and also claim that they have "infrared night vision function", which is completely nonsense. The light transmittance of this coating is very low, the imaging brightness of the telescope is significantly darker, and the red coating reflects the light of a specific wavelength band, which also causes the telescope imaging color to be blue, which is very unfavorable for observation.

These are two different concepts, the former refers to the coating of a single optical element – such as one of the three split achromatic objectives – with a multi-layer film system, while the latter refers to the coating of every optical surface of every optical element in the entire telescope, if the merchant does not exaggerate the claim.

In fact, the latter is more of a commercial slogan, and it appears mostly in low-grade mirrors. Because the refractive optical surface of an astronomical telescope (such as each surface of each lens of the objective lens and eyepiece) must be coated, an optical surface without an anti-reflection coating will cause a large amount of reflection loss of light and cause stray light and ghost image problems; Most of the total reflection prisms used in the zenith mirrors of astronomical telescopes are uncoated because it is an optional element. Therefore, there is no need to take propaganda such as "full coating" seriously.

The concept of multi-layer coating is also quite a bit of a problem in the commercial world. Its original meaning is a complex film system on a single optical surface, which can be a multi-layer broadband anti-reflection coating or a multi-layer anti-reflection coating; But now some businesses say that there is a "multi-layer" coating in the entire lens or even the entire telescope. Strictly speaking, this is already a form of commercial fraud.

There's no need to be so obsessed with these details.

For example, FMC is a very common and ordinary thing, which simply means that a large number of broadband coatings are used, which can be simply thought of.

It's a description: "I use a lot of broadband coatings" – what do you think? Actually, it doesn't mean a lot of things.

When we make a friend, we rarely dwell on and study their nails and fingers, and we will suffer a loss in this kind of research.

Sometimes jump out, macro grasp, for example, whether this business is credible or not, his propaganda is fancy or serious, and he is staring at your wallet and wants you to spend money to buy things. Or does he want you to buy something, but he also explains some technical problems to you in detail and rationally?

These are actually very important.

In addition, if you are interested in telescopes, you can take a look at popular optics, some basic knowledge introduction.