telescopeThere are three main types of telescopes to choose from:

Refracting

Reflecting

Catadioptric

Each of these has it’s own advantages and disadvantages. I’ve explained the differences between these types of telescopes in this article.

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

Refracting Telescopes

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

 

Refracting TelescopeHow Refracting Telescopes Work

How refracting telescopes work is actually very simple. Take a look at the diagram on the right.

 

  • Light enters through a main objective lens at one end (1).
  • The lens refracts (or bends) the light to a point of focus (2).
  • This is then magnified to form an image by the eyepiece at the other end (3).

 

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 however, are more susceptible to aberrations.

 


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, into the eyepiece.

 

Reflecting TelescopeHow Reflecting Telescopes Work

As previously mentioned, the way a reflecting telescope works is similar to reflectors.

 

  • Light enters at one end (1)
  • It is then reflected by a concave shaped primary mirror at the other end (2) towards a smaller mirror known as the secondary mirror.
  • This mirror reflects (3) the light into the eyepiece, which is usually mounted on the side of the telescope (4).

 

Advantages of Reflector Telescopes

These types of telescopes are fairly compact and portable which is great for transportation and storage. They are also generally more affordable too. The mirrors inside can typically produce less optical aberrations than lenses of the same value.

Disadvantages of Reflector Telescopes

Mirrors need regular re-aligning as they can easily slip out of alignment due to knocks and bumps or even temperature changes. In some cases, they can also be susceptible to spherical aberrations.

 


Catadioptric Telescopes

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

 

Catadioptric TelescopeHow Catadioptric Telescopes Work

How a catadioptric telescope works is rather quite interesting.

 

 

Advantages of Catadioptric Telescopes

Most catadioptrics are extremely compact and portable. 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 of the positioning of the secondary mirror (in the middle of the main light gathering primary mirror) but this shouldn’t be a too noticeable, if at all. 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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