How to distinguish the optical quality of astronomical telescope?

Do you know the astronomical telescope? How do you choose an astronomical telescope, do you know? The following Xiaobian photoelectric Xiaobian for you to explain.

First of all, before we introduce how to purchase astronomical telescopes, we need to have a general understanding of astronomical telescopes. Astronomical telescopes are important tools for observing celestial bodies. It is no exaggeration to say that without the birth and development of telescopes, there would be no modern astronomy. With the improvement and improvement of the telescope's performance in various fields, astronomy is also undergoing great leap forward and rapidly advancing the understanding of the universe.

One, type

Optical telescopes can be roughly divided into three categories: refraction, reflection and catadioptric.

Two. Parameters

1, caliber 

2, resolving power and resolving power 

3, magnification 

4, field of view 

5, limit magnitude.

Three, eyepiece

1, Huygens eyepiece (H) 

2, R or SR 

3, Kell eyepiece (K) 

4, Abbe distortionless eyepiece (OR) 

5, proin eyepiece (PL or Plossl) 

6, on the dimension of eyepiece interface

Four. Guide to purchase

一、 kinds of comparison

1, refractive astronomical telescopes are more convenient to use, have larger vision, brighter stars, but have color difference, thus reducing the resolution. The objective of the high quality refracting mirror is two double separate achromatic objective lens or 3 achromatic objective lens. However, achromatic or achromatic aberration does not completely eliminate chromatic aberration.

2, the advantage of the mirror is that there is no chromatic aberration. However, the comet aberration and astigmatism of the mirror are larger, which makes the image quality of the field edge worse. Commonly used mirrors are Newton and Cassegrain two. The former optical system is simple and cheap, the spherical mirror is at the back end and the eyepiece is in the front side. The main and secondary mirrors of the latter are aspherical, the main mirror and the eyepiece are all behind. The imaging quality is better and the price is more expensive.

3. Catadioptric reflection takes into account the advantages of the refracting telescope and the mirror astronomical telescope: large field of vision, good image quality, short lens tube and convenient carrying. Compared with refracted telescopes with equal focal length and equal diameter, the price is less than 1/3. There are two kinds of catadioptric mirrors: Schmidt Cassegrain and Mark's so - called Cassegrain. The horse - Card mirror has two and three pieces of two. For example, the crowns BOSMA1800150 telescope and the BOSMA2400200 telescope are all three pieces, and are more popular with fans both at home and abroad because the image quality is better than the two one.

4. reasonable choice of focal length

Choose the focal length, which is related to the celestial body you want to observe. If you want to observe the nebula and look for a comet, choose a short focal telescope; if you want to observe the moon and planets, choose the long focus telescope; if you want to look at a double star, a star, a variable star, and a star cluster, you'd better choose a medium - focal telescope. The middle focal length mirror can be considered at both ends and is more popular. Usually, the short lens refers to the ratio of focal length to aperture less than or equal to 6. The length mirror is the ratio between focal length and aperture, which is greater than 15.

5. magnification is not as big as possible

According to the experience of long observation by astronomers, the maximum magnification must not be greater than 1.5 times the calibre of the objective lens (in millimeters), and the telescope with a calibre of 100 millimeters is not more than 125 times the medium of medium tranquility in the atmosphere. The best degree of quietness can reach 190 times; when the diameter is 200 millimeters, the observation is not greater than 170 times when the atmospheric tranquility is moderate. At the best tranquility, it can reach 340 times; in fact, the maximum magnification of astronomers can reach two, or even 2.5 times the aperture of the object mirror (in millimeters) for astronomical enthusiasts. However, the large magnification of the astronomical telescope makes the image bigger and darker. At the same time, the jitter of the atmosphere is magnified and the image is blurred.

6.according to the personal economic ability, choose the astronomical telescope with the largest caliber as far as possible.

1) the aperture is large, and more light energy is received, and darker objects can be observed.

2) the aperture is large, and the maximum effective magnification V is large, because the V= primary mirror aperture is D (expressed in millimeter).

3) with large caliber and high resolution, more details of the planets can be observed, which can distinguish binary stars, and may also find darker asteroids and comets. In theory, resolution is only related to caliber, and in fact, it is related to optical design, machining and assembly. The resolution of the general popular science telescope can reach 2 times the theoretical resolution angle. Even if it is a high quality telescope, the crown BOSMA1800150, which is tested by the imported measuring instrument, is better than 1 "and is close to the theoretical value.

7. how to distinguish the optical quality

The day of purchase, you can observe the distance of a building, the building of the contour line moved to the 1/4 view, if the contour line of orange yellow or blue purple especially, or contour bending was particularly severe, do not buy; take a look at the distant leaves, generally 60 mm caliber telescope. Can see a distance of 40 meters Don't buy it clearly. Of course, the larger the aperture, the farther away it is. The BOSMA70060 crown telescope (caliber 60 mm) can see the leaves 85 meters away. In the evening, you can see the stars. If the stars are seen in color and are particularly obvious, or the stars on the edge of the field are dragging their tails, 2 times the size of the stars, the telescope is not suitable for astronomical observations.