The first practical telescope was a refractor with a glass lens, discovered by Galileo in Holland in the early 17th century.  The telescope is the most important research tool in astronomy.  Telescopes enable you to absorb and analyze radiation from astronomical phenomena, including those that are far apart in the universe.  

A lot of people don’t know, what is the classification of astronomical telescopes?  In fact, astronomical telescopes are mainly divided into optical telescopes and radio telescopes. Generally, we are talking about optical telescopes, and optical astronomical telescopes are classified by structure, which can be divided into refraction astronomical telescopes, reflective astronomical telescopes, and refraction astronomical telescopes.  

Classification of astronomical telescopes  

1. Refracting telescopes  

A refracting telescope has an objective lens consisting of a convex lens and a convex eyepiece.  Large double convex lenses collect light from the source, causing them to converge at the focal point, or focal point, that forms the image.  

Refracting telescope objective, is composed of two pieces of the different refractive index of glass lenses, in order to reduce off-color, the image of a red, blue two colors together on the same focus, this kind of lens is called achromatic lens refracting telescopes have high contrast of the image is very suitable for observation, the moon, and the planets, but focusing ability enough to observation nebulae and galaxies such as the “deep-sky objects.  Refracting telescopes have the following advantages:  

First, refracting telescopes are very simple to use.  Just use the star finder to find the target star and focus on the eyepiece to see the target easily.  

Second, refracting telescopes are easy to maintain.  The tube of the telescope is sealed, so you just need to wipe the dust off the surface.  There is no need to worry about moisture or dust entering the tube.  

Third, refracting telescopes are cheap.  You can easily buy a good 150-fold refractor telescope for a couple of hundred bucks.  It can also be used for both heaven and earth. At night, you can watch the moon, Saturn, and other stars.  During the day can be used to see the scenery on the ground, the performance is very good.  

2. Reflecting Telescopes  

Reflecting telescopes use mirrors rather than lenses to collect light.  In a reflector, light travels from the telescope’s barrel to the large concave primary mirror, which reflects light upward to the smaller convex secondary mirror, which reflects light back to the eyepiece.  Reflecting telescopes are shorter than refracting ones because light bounces back and forth rather than traveling in a straight line from one end of the telescope tube to the other.  

The advantage of reflecting telescopes is that they can produce bright images, but for the same money you can buy a larger telescope than a refractor.  However, compared with refracting telescopes, the optical axis of reflecting telescopes is easily changed.  It is relatively large in size and should be taken outdoors one hour before observation to adapt to the external air due to the easy airflow in the tube.  

3. Refraction telescope  

A refraction and reflection telescope is an optical system that combines a refraction system and a reflection system. The light first passes through a lens to produce twists and turns, and then the light is reflected and focused by a mirror. This combination of refraction and reflection optical system is called refraction and reflection telescope.  Its objective lens contains both a lens and a reflector, and the light of the celestial body is refracted and reflected at the same time.  This system is characterized by ease of correction of off-axis aberrations.  Good optical quality can be obtained by adding appropriate refraction elements to correct spherical aberration on the basis of the spherical mirror.  

Because the refraction telescope can take into account the advantages of refraction telescope and reflection telescope, it can not only avoid the chromatic aberration of refraction but also effectively eliminate the spherical aberration of reflection astronomical telescope.  It is very suitable for amateur astronomical observation and astrophotography and has been loved by the majority of astronomy enthusiasts.  

After reading this article, I believe you have a certain understanding of astronomical telescopes.  The last suggestion is: friends who are interested in observing planets and moons, please choose refraction telescopes and refraction and reflection telescopes.  For those interested in nebulae and star clusters, please choose a reflective telescope.  If you can afford it, buy a telescope with as large an aperture as possible, because the larger the telescope, the stronger it is.