According to the Oxford dictionary, the telescope is an optical instrument designed to make distant objects appear nearer, containing an arrangement of lenses or of curved mirrors and lenses, by which rays of light are collected and focused and resulting image magnified. Do you think that this is a good definition of the telescopes?
Well, in my opinion, the answer is “No”, because this just suits for optical telescopes. But they are one type of the telescope among many others such as radio telescopes, infrared telescope, and etc. However as we both know, the optical telescopes are the most popular and common method to observing the sky. So, many different types of optical telescopes can be seen in the market today. Then you may have a real problem when buying a good telescope.
Science of The Telescope
As most of the people think, the Italian astronomer Galileo Galilei invented the telescope. But the truth is different. Though Galileo was the first man who used the telescope for observing the sky, then the inventor of the telescope was Hans Lippershey who was the German-Dutch lens maker.
The story of the history of the telescope will be a good tale to read, but here, we talk about its science.
The telescope works like a human eye. Basically, we can match it together as below.
Pupil – aperture or objective lens
Eye lens – eyepiece
Retina – Observer’s eye
When we see an object in the sky, we can consider that it has an infinite distance from us. Then the “image” through the objective piece of the telescope is on the focal point of the objective piece. Next, the image of the objective lens becomes the object to the eyepiece. Then the observer adjusts the eyepiece as the image seeing in infinity while he looks at the image through the eyepiece. The last image kept in infinity because the observer’s eyes are not getting tired then.
Now I think that you got some knowledge about the mechanism of the telescopes.
Refractor or Reflector?
Though the mechanism of the optical telescopes is the same, we can divide into two categories because of their structures. There are refractor telescopes and reflector telescope
Refractor Telescope
Basically, the refractor telescopes use the glass lens for their objective
pieces and eyepieces. But in this case, the observer has to face some practical issues since the refracting of the light through the glass. As we learned in the physics class when the light ray refracts through the lens, it has to face the incident of light aberration. We can see the edge of the last image turn into blur and rainbow colors. This incident was one of the major problems of the early astronomers and it was a good reason to invent the reflector telescope. But today, the telescope makers use double-glass and it has abled to decrease the rainbow effect.
The refactor telescopes prefer using to observing the deep sky. Since using the lens for the refractor telescopes, they can produce extremely high-quality images. Therefore the refractor telescopes use mostly serious astronomers.
And also, the design of its very simple. You needn’t give extra effort to maintain it. But you have to handle it carefully.
However, refractor telescopes are expensive than others. I think you know why it is. (Hint: High-quality glass lenses) But you can buy them from different ranges of prices and sizes in the market.
Reflector Telescope
The reflector telescopes use the mirrors for their objective pieces and 
eyepieces. The design of the reflector telescope is quite complex than refractors. The curved objective mirror is at the bottom of the telescope and the eyepiece is top of the cylindrical body. Then you already know that it is quite difficult to use for small kids. But, the prices are much less than refractors.
Since the use of the mirrors, you don’t have to face any light aberrations. But you must know that, because of their opened top, the mirror will dirty by dust particles. Then you clean up occasionally.
The reflector telescope is best for observing our solar system. The most popular sky objects such as planets, comets can see sharply. That’s why reflectors are famous among people.
If you are looking for buying a good reflector telescope, I would like to recommend Celestron NextStar 6 SE.
Telescope Vs. Human Eye
As I mentioned before, the telescope works like a human eye. If so, we can apply some facts about the human eye before buying a telescope. Let’s consider it with an example.
The aperture or objective lens is like a pupil of the human eye. The pupil increases its size when we are in dark places because to gather more light. According to this theory, the telescope which has a large aperture can gather more light. So then, you can see more stars instead of a single pinpoint star at once.
Conclusion
Most people are getting trouble when buying telescopes. Many are have no idea about it. They used to consider only about its price, design, technical facts, etc. At that moment, the customer reviews do a great job. We can know about their experiences then. Furthermore, at last, I would like to say that the type of telescope you buy depends on your status and purpose. Then focus your purpose and think more about ” actually, what do you want from it”.
