A telescopeThere are three main types of telescopes to choose from:

Each of these function in its own way and has its advantages and disadvantages. I’ve explained the main differences between these types of telescopes below. It’s a matter of you reading the facts and deciding which of these are important to you and your specific needs.

If there are any terms you are unfamiliar with, please refer to my glossary for an explanation. 

Refracting TelescopesHow a Refracting Telescope Works.

A refracting telescope is the simplest type of telescope and probably the most recognizable. It’s design is so simple, that it is essentially a tube with a lens at each end.


How Refracting Telescopes Work

If you are wondering how refracting telescopes work, it is actually very simple.

(1) Light enters through a main objective lens at one end.

(2) The lens refracts (bends) the light to a point of focus at the other end.

(3) This is then magnified to form an image by the eyepiece which is inserted in the other end of the telescope. The eyepiece can be moved back and forth to adjust the sharpness of the focus.


Advantages of Refracting Telescopes

Because of their simple design, they are generally easy to use and more reliable as their optics are permanently fixed and aligned.

Disadvantages of Refracting Telescopes

They can be heavy, especially larger aperture telescopes, because of their need for large lenses. They can also have a longer body which may impact on transportation and storage.

They may also be more expensive, as large high quality lenses are more costly to produce. Cheaper lenses are more susceptible to aberrations.


How a Refracting Telescope Works.Reflecting Telescopes

A reflecting telescope is similar to a refracting telescope, but just a little bit more complex. It is called a reflecting telescope because it uses mirrors to reflect the light internally.


How Reflecting Telescopes Work

As previously mentioned, the way a reflecting telescope works, is similar to how refracting telescopes work.

(1) Light enters at one end.

(2) It is then reflected by a concave shaped primary mirror at the other end towards a smaller mirror known as the secondary mirror.

(3) This mirror reflects the light into an eyepiece, which is usually mounted on the side of the telescope (4). The eyepiece can be adjusted to alter the sharpness of focus.


Advantages of Reflector Telescopes

This style of telescope is fairly compact and portable which is great for transportation and storage. They are also generally more affordable (particularly as mirrors are cheaper to produce than lenses).

Typically, mirrors can produce less optical aberrations than lenses.

Disadvantages of Reflector Telescopes

The mirrors may need regular re-alignment as they can easily slip out of alignment due to knocks and bumps or even temperature changes.

In some instances, they can be susceptible to spherical aberrations which can interfere with image quality.


Catadioptric TelescopesHow a Catadioptric Telescope Works.

The Catadioptric could be considered a hybrid refracting/reflecting telescope, in that it uses both mirrors and lenses to form the image.


How Catadioptric Telescopes Work

How a catadioptric telescope works is rather quite interesting.

(1) Light enters at one end through a correcting lens, which helps reduce aberrations.

(2) It is then reflected by the primary mirror at the other end back towards the secondary mirror mounted in the center of the corrective lens.

(3) Here it is reflected back towards a hole in the primary mirror and into an eyepiece (4).

When focusing, it is the primary mirror that is moved, not the eyepiece.


Advantages of Catadioptric Telescopes

Most catadioptrics are extremely compact and portable, which makes them easy to transport and store.

The optics provide the advantages of both lenses and mirrors, so they make a great all purpose telescope.

Disadvantages of Catadioptric Telescopes

They may suffer a slight loss of light because the positioning of the secondary mirror places it in the middle of the main opening.

Also catadioptrics may suffer from image shift, or a jump in focus, due to the primary mirror being moved when focusing.


Take The Next Step

If you are ready to begin star gazing, Amazon has a wide range of telescopes to suit all skill levels and budgets. You will find a selection of those currently available, listed below.


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