There are three main types of telescopes to choose from:
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.
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.
How 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.
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.
How 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.
The Catadioptric could be considered a hybrid refracting/reflecting telescope, in that it uses both mirrors and lenses to form the image you see.
How Catadioptric Telescopes Work
How a catadioptric telescope works is rather quite interesting.
- Light enters at one end through a correcting lens, which helps reduce aberrations (1).
- It is then reflected by the primary mirror (2) at the other end back towards the secondary mirror mounted in the center of the corrective lens.
- Here it is reflected (3) back towards a hole in the primary mirror and into the 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. 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.
|Celestron NexStar 8 SE Telescope
|Celestron 127EQ PowerSeeker Telescope
CES1071 Features: -Telescope. -PowerSeeker collection. -Color: Black. -Material: Aluminum. -127 mm (5'') Newtonian reflector. more...
|Celestron 21061 AstroMaster 70 AZ Refractor Telescope
TE3) Celestron astromaster 70AZ scope more...
|Celestron 21068 SkyScout Scope 90mm Telescope with Sky Scout Mounting Braket
90mm (3.5?) diameter refractor, 660mm focal length (f/7), altazimuth mount with pan handle and built-in more...
|BARSKA 40070 Starwatcher Compact Refractor Telescope with Table Top Tripod And Carrying Case
|Meade 20218 NG-70SM 70mm Altazimuth Refractor Telescope
|Celestron 21035 70mm Travel Scope
|Celestron 21024 FirstScope Telescope
FirstScope Telescope Official Product of the 2009 International Year of Astronomy. Ideal astronomical entry more...