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Types of Telescopes

There are three main types of telescopes available to the astronomer, both for visual (look through eyepiece) astronomy and for imaging astronomy (astrophotography with digital cameras):

Refractor telescopes

These are the classic "department store look" telescopes that use refracting lenses housed in a long, thin tube. Refracting telescopes are great for viewing the sun, moon and planets where magnification detail is important but brightness is not. Smaller achromatic versions are used as finder or spotting scopes, while more expensive apochromatic (APO) designs have often been used in astrophotography.

Achromatic - feature a single lens (singlet), and are the cheapest telescope design. Solar scopes are of achromatic design with a built-in filter for viewing the sun.

Apochromatic (APO) - feature 2 lens (doublet), three lens (triplet), and four lens (Petzval) designs. APO scopes are significantly more expense then achromatic designs.

Reflector telescopes

These are larger telescopes that use mirrors housed in long large tubes or trusses. They are often mounted in a low "rocker" style mount (called a Dobsonian). Larger reflecting telescopes are referred to as "light buckets" and are great for viewing faint, deep-sky objects like galaxies, star clusters and nebulae.

Newtonian - have an equatorial mount

Dobsonian - have a low "rocker" style mount

Cadioptric telescopes

Also called compound telescopes, these use both refracting lenses and reflecting mirrors in their design to provide a more compact form factor and correct for various distortions. Compound telescopes include those of Schmidt, Cassegrain (Cass), Maksutov (Mak), and hybrid designs like the Ritchey-Chretian (RC). The latter can be quite expensive and are often used at research institutions for advanced astrophotography usage. Scopes used for astrophotography are called astrographs.

Schmidt-Cassegrain (SCT) - compact design, most common form of compound telescope for visual astronomy

Maksutov-Cassegrain (MCT) - compact design for visual astronomy

Maksutov-Newtonian (MNT) - used for amateur astrophotography

Dall-Kirkham (DK) - expensive design used for professional astrophotography

Rowe-Ackermann Schmidt Astrograph (RASA) - used for advanced amateur astrophotography

Ritchey-Chretian (RC) - very expensive design used by large research institutions

Harmer-Wynne - very expensive design used for advanced professional astrophotography

Riccardi-Honders - very expensive design used for advanced professional astrophotography

The following lists the more common types of telescopes and their approximate starting prices:

      1. Telescope Type
      2. Aperture range
      3. Starting Cost
      1. Equatorial Newtonian
      2. 4.5" - 16"
      3. $300
      1. Schmidt-Newtonian
      2. 5" - 16"
      3. $600
      1. Maksutov-Newtonian
      2. 3.5" - 10"
      3. $400

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