Development history
FRIAL is the earliest form of optical telescope, the first practical refraction telescope appeared in the Netherlands in 1608, from three Different people, Mirror Manufacturer Hans Lipyi and Yang Sen, and Alkyo, Alkyo, and Alone inventions. Galileo has heard of this invention in Venice around May 1609, and has improved and made its own telescope according to the understanding of the refraction. Then Galist will publicize his inventive details, and to show the instrument to the Venice Mado Palto at the time in all parliaments. Galileo may claim to inven invented a refractive telescope independently, and not heard others also do the same instrument.
But this telescope is a positive image, and the exit pupil is between the eyepiece and the objective lens, the field of view is smaller, and it is inconvenient to place aiming fork, so it is used in astronomy. It is called a Copler telescope with a convex lens as a eyepiece. Since the outlet light in the Copler telescope is outside the eyepiece, it can obtain a large field of view, and there is no need to be aimed at the fork, and there is no impact on the observation of astronomy. Therefore, from the middle of the seventeenth century, astronomy The family is generally used with a Copler telescope.
Unfortunately, other defects in refractive telescope design have become their fatal injuries. In order to shorten the focal length of the lens, people have to increase the thickness of the lens, but the dispersion and phase difference have been discovered.
To ensure a clear image in the telescope is formed in the telescope, the key is that the objective lens must focus the light from any point on the object into one focus. If this is not available, the light from the different places will be slightly scattered to different focus, then this object will look very vague. However, the single-chip microscope is manufactured in any glass, it is not possible to focus all light in the same focus. Everyone knows that ordinary light, whether it is from the sun or from the star, is a mixture of different color light waves, each of the wavelengths of each wavelength difference, while the light wave of different wavelengths passes through a single-chip lens, will be Gather up to a slightly different focus. Astronomers in three hundred years ago, there is no way to avoid the dispersion of the lens, and only the effects of the dispersion can only be reduced by lengthening the length of the telescope.
Another problem with an early refractive telescope is different. Compared with modern technology, the technology of the grinding lens is still rough. As long as the light is slightly deviated at the time of grinding, the light is not properly collected by the lens; at the same time, due to its own weight of the lens, it will also be deformed after it is mounted to the lens barrel, which is deformation. The pure glass required for lens is also difficult to manufacture.
Until about 1750, London's Dollard invented a method to avoid dispersion, that is, using two different glass, one is a coroned glass, a rock glass. The principle of this method is simple. The refractive ability of the corona glass is similar to the rock glass, but the dispersion capacity is almost doubled. Since Dolone has made a mirror with two lenses, a part of the front part is a mirror of a crowning glass, which is connected together is a graft of a rock glass. Since the curvature of the two lenses, the light will be shot in different directions. The bowel glass is concentrated in a point, and the graft of the rock glass is dispersed. If you use rock glass, we will see that the light passes it, not only is not concentrated, but it is gradually spread from a point to each direction. The focus of this rock glass is made in just a larger than half the focus of the crown glass. This clever design is enough to eliminate the dispersion of the corpus glass; but it can't eliminate half of its refractive ability. The combined results are all light pass, which are almost concentrated in one focus, but this focus is more than doubled than the single-use coroned glass.
We said "almost concentrated in one focus", because the two-layer glass is combined, and the light of all colors is absolutely concentrated on the same focus. The bigger telescope is bigger, and this disadvantage is serious. If you look at the moon or a bright star from a large refraction telescope, you will see you have a blue or purple dizzy around them. These two-lens cannot focus on the same focus of the blue or purple light to the same, thereby producing aberrations called "secondary spectrum". This is determined by the nature of general optical glass, and scientists have no way.
Since then, until today, the basic design of the refractive telescope has almost no change, but the glass quality of the manufacturing lens has improved a lot, and it is already possible to correct dispersion and phase difference. The only thing that cannot be overcome is deformed by the lens itself under gravity, because of this reason, we have not manufactured huge refractive telescope.
Design Classification
Summary
There are two basic components, as an objective lens and eyepiece, refracting the objective lens in the telescope, Light refractive or deviating to the rear end of the mirror. Refraction can aggregate parallel light on the focus, not parallel light, aggregate to the focal plane. This makes the distant objects look brighter, clearer and larger. Refractive telescope has many different aberrations and deformations that require different types of corrections.
According to the difference in the optical path, the refractive telescope is divided into Galileo telescope and the Kaipuji telescope. Generally, the relative diameter of the refractive telescope is smaller, that is, the focal length, the negative slice is large, so that the resolution is high, it is suitable for the work of the heavens (such as the position of the star, the position of the two star, etc.). The initial design of the refractive telescope is used for investigating and astronomical observations, but is also used in other equipment, such as a binoculars, telephoto camera lens. There are two forms of optical systems for more commonly used refractive telescopes: that is, garavailability telescope and Coppler telescope, the advantage is that the imaging is relatively distinct; the disadvantage is to have a color difference.
Refractive telescope Working principle
refractive telescope is a telescope generated by the refraction principle of light. This video will systematically introduce the basic principle of refractive telescope: light from the object we have seen, then, after it passes the lens of the telescope, focuses on the focus, then shoot the telephoto mirror, generate image rebirth.
The shortcomings of the refractive telescope are that it will change the color of the light, since the light is by the spectral group, and the spectra has its own specific wavelength, so that the light of the various colors does not produce The same refraction, the lens refractive telescope changes the direction of the light by focusing, but not all colors will completely fall on the focus of the telescope, but is scattered to other places to form chromatography. Difference. Of course, you can use the refractive lens group to change this phenomenon.
Galileo telescope
The same telescope as the original form of Galileo is called Galileo telescope. He uses convex lens to make objective glasses, and the eyepiece of the concave lens. The image of the Galileo telescope is correct, but the field of view is limited, there is a spherical aberration and color difference, and the Eye Relief is not good.
Copler telescope The Copler telescope is Copper to improve the design of Galileo, invented in 1611. He changed a convex lens as a detective mirror instead of a concave lens for Galileo. The advantage of this is that the light from the eyepiece is aggregation, and there can be a large field of view and a larger anxiety, but the image seen is reversed. This design can achieve a higher magnification, but it is necessary to high coke ratios to overcome the distortion caused by the mirror. (John Hevie rejuvenated a 40-meter refraction mirror with a 45-meter focus.) This design also uses on the graft on the focal plane (for measuring the size of the angular distance between the two objects observed).
Palelenoliosis Filling Mirror
The color of the color difference is in 1733 by a British lawyer Chester Murha Hall. Although the patent is given another independent invented John Dollond. This design uses two glasses (with different columns "" bowel glass "and" rock glass ") to reduce color difference and spherical aberration. Each surface of the two glasses should be polished, then combined together. The chromoosel lens allows two different wavelengths (usually red and blue) to focus on the same focal plane.
Height Squiry Differential Film
High mesencing reflection mirror uses a particular material, particularly low-color material, to make objective lenses. His design allows three different colors (usually red, green, and blue) to gather on the same focal plane, and the residual error of the color (secondary spectrum) is less than a quantity level than the chromoosome lens. The primary mirror of this telescope is a lens of fluorite or ultra-low dispersion (ED) glass, which produces a very clear image. This telescope is a very high value product in the amateur astronomical telescope. The caliber of the highly color varnish variable light mirror can be achieved by a diameter of 553 mm, but most of them are still between 80 and 152 mm.
Features
Advantages
Easy to use, simple manufacturing.
Suitable for observations, planets, double stars, especially for large diameter telescopes.
The structure is small, no additional maintenance costs are required.
The closed lens barrel reduces the damage of the air flow to the imaging quality while protecting the optical lens.
is easy to carry, suitable for far-distance outdoor observations.
can avoid secondary imaging to form a high contrast.
The color difference can be avoided by the color difference design.
Disadvantages
The price is expensive than the Newton or the card.
Under the same diameter, the refractive telescope is more heavy, longer and larger in the Newtonian or Card Grind.
Due to the limitations of the caliber, it is not suitable for observation of deep spaces such as river alien, nebula and so on.
The disadvantage of focal is more difficult to take a refractive telescope to shoot deep space.
In the color difference design, the color of the resulting image will also have a little distortion.
Technology
Refractive telescope once suffered from high-residual color difference and spherical aberration, the short focus is more serious than telephoto. A 4-inch F / 6 color-coloniment light mirror may still have a colored scatter phenomenon that cannot be ignored (usually with purple gratin near the bright celestial body), while 4 inches f / 16 only There will be a little dispersion.
in a very large diameter fuel lator, there is a problem of lens subsidence, which is the result of gravity to deform the glass. The glass of glass is a further problem, trapped in air bubbles or stripes in the glass. In addition, glass is opaque to certain wavelengths, even if it is visible, it is bleak due to absorption and refraction when the entry and exit interface is penetrated. Most of these problems can be eliminated or decreased by switching to mirrors, and more capable of manufacturing a larger diameter.
Applicable field
Like other telescope, the size of the objective lens for collecting the light is the key to refractive telescope. The larger the objective lens, the more clear the objects of the far. However, due to technical issues, it is impossible to reflect the objective glasses of the telescope.
Due to the refractive telescope is sealed, the influence of environmental factors such as air on the flow of air, we can see a clear and stable image, so that the refractive telescope is suitable for observing the planet and the closer star. In addition, we also rarely adjust the optical components of refraction telescopes, which is more convenient to use.
Another advantage of refraction telescope is that it is suitable for astronomical observations and ground observations. After the eyepiece end of the refractive telescope is installed, after observing the ground object, we can see the normal image.
The size of the compact refractive telescope is very suitable for tourists carry, such as people who are generally used in binoculars are all combined with two refraction telescope.