There are 3 main types of telescopes and each one performs differently and may be used for different purposes. If you are thinking about buying a telescope to look at stars and deep space then you should know that this might not be possible if you live in a built up area with light pollution. If it is just the moon and the planets you want to look at then you should now that refractors are better than reflectors for this. If you are prepared to travel with your telescope then you should know which types are fragile and which ones give you the best performance from a smaller scope.
The three types of telescopes that exist for capturing light so that it may be magnified for viewing are Catadioptric, Newtonian Reflector and Refractor.
Refractor Telescope
The traditional long-tube looking telescope. The Refractor uses lenses to bend light and this causes the rays to meet at a point on the other end of the telescope. They are magnified by the eyepiece for viewing. There is a large lens on the front of the Refractor, which is the objective lens.
Pros
Requires little to no maintenance
Excellent for planetary viewing
Cons
Color deviation in achromatic designs
Not recommended for deep sky observation
Reflector Telescope
The Newtonian Reflector uses a primary mirror that is concave. This mirror sends light to a flat mirror which reflects the light out a side opening and to the eyepiece where it is magnified and focused.
Pros
Best for deep space observation - Great for looking at remote galaxies
Delivers very bright images
Cons
Requires regular alignment
Requires more complicated cleaning of mirrors than other types of the same design
Catadioptric Telescope
The last of the three types of telescopes and currently the most popular on the market. This type uses a series of lenses and mirrors that fold the light path and send it through to the primary mirror through a small hole. This allows the light to be magnified and focused for viewing. There are two types of Catadioptric telescopes - Schmidt-Cassegrain and Maksutov-Cassegrain. The Maksutov type has a concave and convex correcting lens where the light enters. The light hits the primary mirror, is sent back to the secondary mirror and finally sent to the opening in the back of the telescope.Pros
Portable and easy to use
Versatile - good for deep space and planetary observation
About the best for focusing
Excellent optics
Cons
It does not look like a telescope to many people
It is more costly than other Newtonians with the same size opening for light
Once you know what you want to look at and which of the types of telescope you should choose you need to think hard about how much you are prepared to carry around, telescopes can be bulky and your tripod and mount are essential bits of additional kit. Size determined, you are now ready to see just how much aperture you can get for your money. Don't concern yourself with magnification, it is not nearly as important as is touted and higher magnifications will cause images to be blurry because of air turbulence. The performance of a telescope depends on how much light gathering capability it has, the more light it can gather the better you will see, and this is aperture. As a general rule of thumb, once you know which of the types of telescopes is best for you, get the biggest aperture you can afford for your money.
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