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):
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.
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
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
Schmidt-Newtonian (SNT) - used for amateur astrophotography
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 various types of telescopes and their approximate starting prices:
- Telescope Type
- Aperture range
- Starting Cost
- Achromatic refractor
- 2.4" - 6"
- Apochromatic refractor
- 3" - 8"
- Equatorial Newtonian
- 4.5" - 16"
- Dobsonian Newtonian
- 4.5" - 30"
- 5" - 16"
- 5" - 16"
- 3.5" - 10"
- 3.5" - 10"
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