The 9 types of telescope (and their characteristics)

The year 1609. Galileo Galilei, the Italian physicist, and father of modern astronomy, responsible for proving that the Earth revolves around the Sun, did something that would forever change the history of science and our way of seeing the Universe. He had invented the telescope.

From that moment in which Galileo Galilei was able to observe the Moon, Jupiter, the stars, and the Milky Way itself, a new era began for humanity. At last, we had an instrument that allowed us to look beyond the limits of our planet. The telescope is a fundamental tool for astronomy and has helped us understand the nature of the Cosmos.


It is precisely thanks to the invention of the telescope that we are no longer blind. And since then, over 400 years, its technology has evolved a lot, thus having telescopes that are true works of engineering and that allow us to see galaxies located millions of light years away.

But obviously not all telescopes are the same . And if you are an astronomy fan, you have come to the right place, because in today’s article we will analyze the different types of telescopes, seeing what their characteristics are and for what purposes they have been developed. Let’s go there.

What is a telescope?

A telescope is an optical instrument that allows you to observe distant objects and astronomical bodies with much more detail than with the naked eye. In other words, it is a tool capable of capturing electromagnetic radiation , such as light.

Telescopes have the ability to process electromagnetic waves (including those in the visible spectrum), which leads us to emphasize that, despite the general idea that a telescope increases the size of objects thanks to a series of lenses, it is very entrenched, this is not true.

In other words, telescopes do not amplify an image through magnifying lenses, but rather collect the light (or another form of electromagnetic radiation) reflected by the astronomical objects in the Universe that we want to observe and, after processing this light information, reconstruct it in image form. They do not magnify an image. They build one from the processing of the electromagnetic waves they capture .

And in this sense, we must make one thing clear. We have said that telescopes are optical instruments. And this, despite the fact that it is true in the general idea that we have of a telescope, is not exactly true. The truth is that optical telescopes are just one type of telescope in which the electromagnetic radiation that is captured corresponds to the waves of the visible spectrum (light), but this is not always the case. There are telescopes that process infrared, ultraviolet or radio waves, so they are not optical.

Be that as it may, the important thing is that these instruments capable of capturing and processing electromagnetic radiation allow us to observe celestial bodies in great detail from the surface of the Earth or from space, collect information about astronomical events and physical laws and discover new stars , planets, nebulae and galaxies.

How are telescopes classified?

There are about 80 different types of telescopes, but the differences between many of them are subtle and relevant only from a very technical point of view. For this reason, we have collected all these types and have grouped them into basic families based on both the type of electromagnetic radiation they can process and their fundamental design. Let us begin.

1. Optical telescopes

Optical telescopes are basically the ones that come to mind when we think of a telescope. They are those capable of processing the part of electromagnetic radiation that corresponds to the visible spectrum , which is found in wavelengths between 780 nm (red) and 380 nm (violet).

In other words, they are the telescopes that capture the light that comes from the astronomical bodies that we want to observe. These are tools capable of increasing both the apparent size of objects and their brightness. And depending on how they manage to capture and process light, optical telescopes can be of three main types: refractors, reflectors or catadioptric.

1.1. refracting telescope

The refracting telescope is a type of optical telescope that uses lenses to form the image . Also known as dioptric, they are the ones that were used until the most technologically advanced ones were introduced at the beginning of the 20th century and those that are still used by amateur astronomers.

refracting telescope

It is the best known type of telescope. It is made up of a set of lenses that capture light and concentrate it in what is known as a focus, where the eyepiece is placed. Light refracts (changes direction and speed) as it passes through this converging lens system, causing parallel light rays from a distant object to converge on a point on the focal plane. It allows you to see large and bright distant objects, but it is quite limited technologically.

1.2. Reflecting telescope

The reflecting telescope is a type of optical telescope that uses mirrors instead of lenses to form the image . It was first designed in the 17th century by Isaac Newton. Also known as catoptrics, they are especially common in amateur astronomy, although professional observatories use a variation of it known as Cassegrain (discussed later), which is based on the same principle but with a more complex design.

Reflecting telescope

Be that as it may, the important thing is that they are made up of two mirrors. One is located at the end of the tube and is the one that reflects the light, sending it to the mirror known as secondary, which, in turn, redirects the light to the eyepiece. It solves some problems of the refractors since by not working with lenses some chromatic aberrations are solved (there are not so many distortions in the brightness) and they allow to see more distant objects, although their optical quality is inferior to that of the refractors. For this reason, they are useful for seeing more distant objects with a weak brightness, such as galaxies or deep nebulae.

2. Radio telescope

We completely changed the terrain and went on to analyze telescopes that, despite being telescopes, surely do not correspond to the image we have of a telescope. A radio telescope consists of an antenna capable of capturing electromagnetic radiation that corresponds to radio waves, which have a wavelength of between 100 micrometers and 100 km. It does not capture light, but the radio frequency emitted by astronomical objects

Radio telescope

3. Infrared telescope

The infrared telescope consists of an instrument capable of capturing electromagnetic radiation that corresponds to the infrared, whose waves have a wavelength of between 15,000 nm and 760-780 nm, thus limiting the red color of the visible spectrum (hence known as infrared). Again, it is a telescope that does not capture light, but infrared radiation. These not only completely eliminate interference with the Earth’s atmosphere, but also give us very interesting information about the “heart” of galaxies.

Infrared telescope

4. X-ray telescope

The X-ray telescope is an instrument that allows you to “see” celestial bodies that emit electromagnetic radiation in the X-ray spectrum, whose wavelengths are between 0.01 nm and 10 nm. They allow us to detect astronomical objects that do not emit light, but rather what is popularly known as radiation, such as black holes . As the Earth’s atmosphere does not allow these X-rays from space to penetrate, these telescopes must be installed on artificial satellites.

X-ray telescope

5. Ultraviolet telescope

The ultraviolet telescope is an instrument that allows us to “see” astronomical objects that emit electromagnetic radiation in the ultraviolet spectrum, whose wavelengths are between 10 and 320 nm, so it is a radiation close to X-rays. Be as In other words, these telescopes shed very valuable information about the evolution of galaxies , as well as white dwarf stars.

6. Cherenkov Telescope

A Cherenkov telescope is an instrument that can detect gamma rays from incredibly energetic astronomical objects , such as supernovae or very active galactic nuclei. Gamma radiation has a wavelength of less than 1 picometer. Currently, there are four telescopes of this type in the world and they provide very important information about these astronomical sources of gamma rays.

Other Article:

Laws Of Physics

Differences between Astronomy and Astrology


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