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How Telescopes Work


What Type of Telescope Do I Need?

The type of telescope that you need depends mostly on the observing you want to do. Many amateur astronomers own more than one telescope, each specialized for a different type of observing. But if you are a beginner, you might want to look for a telescope that you can use for several different activities.

Remember that there are three basic types of telescopes:

  • Refractors - a lens is the primary device for gathering light.
  • Reflectors - a mirror is the primary device for gathering light.
  • Compound telescopes or catadioptrics - a combination of lenses and mirrors is used to gather light.

Each type has advantages and disadvantages with respect to optical quality, mechanical performance, maintenance, ease of use and price.

To help with matching the telescope type to the type of observing you plan to do, we have prepared a table that relates the design and aperture to the observing use (moon, planets, deep-sky, etc.).

Generally, refractors are good for lunar and planetary observing, while reflectors are good for deep-sky observing. Compound telescopes are good general observing instruments.

You should also consider where you will do most of your observing:

  • light-polluted urban skies - compound telescopes and refractors tend to do better than reflectors.
  • moderately light-polluted suburban skies - all types tend to be equal.
  • dark, rural skies - compound telescopes and reflectors tend to be slightly better than refractors because they are better able to collect light.

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