Hobbies And Interests
History
The first telescopes known to function were refractors, made in the early 1600s. Their invention is attributed to Hans Lippershey, but by reorienting and modifying the designs of the lenses, notable astronomers Galileo and Kepler created their own versions. Throughout the course of history, individuals have experimented with the materials used to compose refractory lenses, but the principle is still the same.
How do they work?
Basically, a refractor telescope consists of a tapered tube and a lens placed inside either end of the tube. The larger lens (referred to as the objective lens) is a convex piece of glass, which bends light to a central image inside the tube. The smaller lens is the eyepiece, which magnifies the image.
Size
It is difficult and expensive to make large lenses for refractor telescopes; lenses typically do not exceed 8 inches (200 mm) in diameter. Bodies of refractor telescopes vary in length, often ranging from 1 to 5 feet long.
Cost
Because of the difficulty in making refractor telescope lenses, refractor telescopes tend to be more expensive than their reflector counterparts. A 4-inch refractor telescope may cost $500 to $1,000, a 6-inch refractor $3,000 to $6,000 and an 8-inch refractor may cost more than $10,000. An 8-inch reflector only costs about $1,000.
Perks
Refractor telescopes do not require much upkeep; they are closed tubes and are thus not susceptible to dust, elements, atmospheric changes or jostling.
Drawbacks
Refractor telescopes, because they operate by bending light, may cause chromatic aberration--that is, objects viewed through these telescopes may be discolored or may be encircled by a rainbow-colored ring of light. Glass is also an imperfect material and over the course of years, the objective lens may "sag," causing images to appear distorted.