Refractor Telescope

in

Refracting Telescopes use lenses to gather light and bring the image to the eyepiece. They are fairly maintenance free and generally provide superb images of the moon, planets, star clusters and general sky gazing. They tend to be smaller in aperture than other types so they are not as good for viewing fainter sky objects such as galaxies and nebulae. Good quality refractors tend to be expensive.

 

There are several types of refracting telescopes

  • Achromatic - Achromatic refractors are generally inexpensive and suffer from chromatic aberration.  When light passes through a refractor lens, it is bent to reach a focus point at the back of the telescope.  Each wavelength of light is bent by a slightly different amount.  Thus, red, green, and blue wavelengths do not necessarily focus at the exact same position.

     

  • Apochromatic - Apochromatic refractor lenses are designed so that at least three colors of lights (rather than just two) reach the same focus.  They are designed such that the difference between the primary focus point and the focus point of the remaining colors (such as violet) is extremely small.  In this way, chromatic aberration and secondary color is essentially eliminated. This style is popular for asrto-photography.

 

A small, quality achromatic refractor of 60mm to 80mm aperture makes a fine starter scope for observing the Moon and major planets. They’re inexpensive ($100 to $350), portable, and maintenance-free — all desirable factors if you’re just “testing the waters” of the hobby. Their small apertures aren’t well suited for faint deep-sky objects, though. If nebulas and galaxies are your main interest, a Newtonian reflector or Schmidt-Cassegrain is the way to go. Moving up to a 90mm or 100mm refractor will snare more objects and provide better performance, for a higher price. Renowned for crisp, sharp images, refractors are the priciest per inch of aperture of all telescope types. A refractor is the scope of choice if you will be doing most of your stargazing from city or suburbs, where the night skies are moderately light-polluted. Here, more aperture doesn’t gain you much, since viewing is restricted mostly to the Moon and planets. In fact, a big scope would only amplify the skyglow, yielding poor washed out images.