Telescope Types | A Guide For Beginners

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Telescopes come in many different shapes and sizes. Since there are so many out there, it is important for beginners to know about different telescope types. You will encounter three basic types of optical telescopes while searching for one. Each of them has its own set of features and pros/cons which I will discuss below.

Refractors

It was the first telescope that Galileo built and used to observe the night sky. A refractor is exactly what most people think of every time the word telescope is mentioned. It is the stereotype of what a telescope is supposed to look like, a long tube with a large lens in the front and an eyepiece in the back. The principle upon which a refractor works is that the front lens also known as the objective produces an image in the back by focusing light. The eyepiece is then used to magnify and view this image.

Refractors have some advantages over other telescope types. The biggest benefit of a high-quality refractor is that it can produce crisp and high-contrast images of the Moon and other planetary bodies. A well-made refractor telescope is capable of showing some of the finest details possible with a given aperture.

These telescopes are also pretty rugged since the lenses are less prone to come out of alignment. This makes them a good choice for people who need a scope that doesn’t require much tinkering. However, refractors are quite expensive since large objective lenses require special glass and hand-crafting. They can also become quite unwieldy because of their longer tube lengths.

Pros

  • Simple and easy to use and setup.
  • Crip and high-contrast images for lunar and planetary viewing.
  • Tough and rugged for normal use.

Cons

  • Expensive because of their objective lenses.
  • Length can make them unwieldy to use.
  • Fainter night-sky objects might be difficult to view.
  • Field of view might be narrow.

Reflectors

The second type of telescope that is used widely is the reflector. As the name suggests, it uses a mirror to gather light and then focus it. Sir Issac Newton invented the Newtonian reflector which uses a special concave primary mirror at the bottom of the scope. A small diagonal mirror near the top directs light from the primary mirror to an eyepiece on the side of the tube.

A reflector should be considered if you need the most aperture for your money. They can easily provide sharp images of all different types of celestial objects while costing a small fraction of what an equal-aperture refractor would. Newtonian’s also have more manageable tube lengths making it easy to fit them in the car for easy transportation to areas with dark skies.

Another particular type of reflector is the Dobsonian which is basically a Newtonian mounted on a simple and sturdy mount. These telescopes are available in apertures ranging from 4 inches to 30 inches. The Orion Skyquest XT8 is an example of a Dobsonian reflector.

Unlike refractor telescopes, reflectors like the Newtonian need to have their mirrors aligned every once in a while, a process known as collimation. Its a fairly easy process once you figure out how to do it but it might frustrate those who are not looking to tinker with their scope. Reflectors are also very prone to dust and dirt because of the open tube design so they need to be cleaned occasionally.

Pros

  • More aperture size for your money.
  • Suitable for all types of stargazing.
  • Easy to transport and less unwieldy.
  • Provide sharp and high-contrast views.

Cons

  • Mirrors can go out of alignment, requiring occasional collimation.
  • Prone to dirt and dust so they need to be cleaned every once in a while.
  • Mirrors may need recoating after 10-20 years.

Catadioptric/Compound

Among the different telescopes out there, compound telescopes combine the best features of both refractors and reflectors. They use a combination of lenses and mirrors to produce images. The biggest advantage of compounds over other telescope types is that they are extremely compact. This makes them very easy to transport and they can work with smaller and much lighter mounts.

Compound telescopes are capable of delivering very fine quality images of different night-sky objects which makes them ideal for astrophotography. They end up being highly versatile telescopes capable of using a large number of accessories.

However, they also have quite a few disadvantages compared to other telescope types. Similar to Newtonian telescopes, compounds also need occasional collimation and sometimes their field of view can be quite narrow. The presence of a secondary mirror in the light path can also end up reducing their performance during planetary and lunar observations.

Pros

  • It combines the advantages of both refractors and reflectors.
  • It is compact and easy to transport.
  • Compounds are ideal for astrophotography.

Cons

  • Will need occasional optical collimation.
  • The field of view can be quite narrow.
  • Its performance can be slightly reduced while viewing the moon and planets.

Choosing Between Telescope Types

Before deciding which type of telescope you should consider buying, it is important to weigh all of their pros and cons. A refractor is great for people looking to observe the moon and planets but who don’t wish to tinker with their scope. Reflectors are much cheaper and can easily view deep-sky objects but require an occasional mirror alignment procedure known as collimation. Similarly, compound telescopes combine the features of both refractors and reflectors but they can have a narrow field of view and also need collimation. Choosing the right telescope is a big decision so it is important to take your time with it and consider all your options.

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