Reflecting telescope

example of reflecting telescope

Un Reflecting telescope works through mirrors. The larger primary mirror at the bottom of the tube transmits light to the smaller secondary mirror, which in turn directs the light to the eyepiece and forms the image we will see through it. These telescopes are perfect for those starting out in the world of astronomy and observing the universe.

Therefore, in this article we are going to tell you all the characteristics, advantages and disadvantages of a reflecting telescope.

Who was the inventor of the reflecting telescope?

Reflecting telescope

Although many people contributed to the invention of the reflector, Isaac Newton was the first to create a telescope that used mirrors instead of lenses to reflect light, and the first alternatives to refracting telescopes with chromatic aberration emerged. Furthermore, when the reflecting telescope was invented, it became possible to create telescopes with larger apertures, allowing fainter and more distant objects to be discovered.

Advantages and disadvantages of a reflecting telescope

Although there are many types of reflectors, and each type is best suited for certain uses and has its own advantages and disadvantages, there are often certain advantages or disadvantages that occur with different models.

Advantages of reflectors

  • The first great advantage of reflectors is that They have a larger aperture and are less expensive than reflectors (mirrors are easier to find and manufacture than lenses, which reduces the cost and allows you to find them for less than 200 euros Powerful reflector model)
  • They are completely free of the chromatic aberration that refractors suffer from. Light is reflected rather than refracted, resulting in color separation in shiny objects.

Disadvantages of reflectors

  • Mirrors do not reflect 100% of light. This means that some brightness and contrast is lost in the image. In this sense, not all reflectors are the same, and many of them have special coatings on their mirrors that allow light transmission of approximately 90 to 95 percent. Without these coatings, light loss can reach 20%.
  • They require frequent alignment. Some models even require this before each use.
  • They may suffer from other optical aberrations such as astigmatism, spherical aberration and coma.

Types of reflecting telescopes

refractor and reflector

Although the term "Newtonian telescope" is often used to refer to reflecting telescopes, and Newtonian telescopes are in fact the most widely used model. There are two types of reflecting telescopes: Newtonian telescopes and Cassegrain telescopes.

Newtonian reflector telescope

This type of telescope was invented by Isaac Newton and had an amazing ability to capture light. It is also a model widely used by astronomy students, as it offers an unmatched price-to-openness ratio. Consider that you could buy a Newtonian mirror with twice the aperture of a refractor for the same budget.

In addition, mirrors with a focal ratio greater than 6 will provide spectacular images of the moon and planets, certainly comparable to refractors or catadioptric telescopes (both designs are much more expensive than Newtonian mirrors). Additionally, reflectors with these properties will allow you to see many deep sky objects. This is a great option for a variety of terrain, making it perfect for beginners.

Which ones do the most advanced astronomers use?

Many of them also believe that Newtonian reflectors are a good option. For example, A 200mm telescope will perfectly meet the needs of the most demanding astronomers without being too bulky to transport.

If you live in a city, you may have to travel to dark places to avoid light pollution, so there is no point in having a telescope larger than 180mm as it will be difficult to transport. Of course, Newtonian mirrors have more than just advantages. One of the problems they have is that they are the type of telescope most susceptible to decollimation, so care must be taken at the beginning of each observation.

The higher the focal ratio, the less likely it is to be out of focus. This may be another reason to choose a Newtonian reflector with a focal ratio of 8 as your first telescope.

Cassegrain reflector telescope

telescope to look at the sky

Cassegrain telescopes are ideal for lunar and planetary observations. Due to the structure of the mirrors, Cassegrain telescopes They allow high focal ratios to be combined in a tube that is more compact and easier to handle than Newtonian telescopes.

Some disadvantages of this model are that it is more difficult to collimate (due to its more complex optical structure) and is prone to coma (the periphery of the image will not appear sharp).

Since the eyepiece is located at the end of the tube, it is useful for observing objects relatively close to the horizon, but it will be uncomfortable to observe near the zenith. In this case you should use a diagonal star, which will make your observations more comfortable.

In addition to the classic Cassegrain telescope, we have other less known but also interesting models:

  • Richtey-Chretien: The goal of this design is to eliminate coma and reduce the focal ratio.
  • Dall Kirkham: It provides excellent images, but has a smaller field of view.

Both the Richtey-Chretien and Dall-kirkham are excellent telescopes for astrophotography because they eliminate coma and produce very clear images.

In short, the Cassegrain reflector is not usually the first choice for beginners, but although it is not as common as a Newtonian telescope, many professionals use it, and it has its advantages, such as being great for observing planets.

Many astronomy beginners choose mirrors for their lower cost and larger aperture. Although it has some disadvantages, for many hobbyists the advantages outweigh the possible disadvantages, since they allow them to start observing a very diverse range of objects without spending a lot of money.

If you are starting to study astronomy, a Newtonian reflector is undoubtedly a very good choice. If you are particularly interested in observing the solar system and have some experience with planetary observations, the Cassegrain telescope may be the telescope you are looking for to discover more details.

I hope that with this information you can learn more about the characteristics of a reflecting telescope and its advantages and disadvantages.


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