Refractor Telescope Information

Basics

• Telescopes are either reflectors or refractors. The type of telescope depends on the objective, the part of the telescope that collects light. Refractors use glass lenses as an objective. The glass bends the light, a process called refracting. A glass lens is at the front of a telescope, and it gathers and focuses the light.

History

• The earliest telescopes, including Galileo's telescope and the spy glasses, were refracting telescopes. Originally, refracting telescope was created in the 1600s in the Netherlands. The inventor was Hans Lippershey. People once believed Galileo invented the first refracting telescope, but he actually learned about the telescope in the Netherlands and constructed his own using his knowledge of light. Hans Lippershey came up with the idea of the refracting telescope after he noticed that far-away objects appeared closer when he looked at them through a concave lens and a convex lens that he held in front of each other.

Durability

• Refractor telescopes will continue to work well under conditions that would break a reflector telescope. The optical system resists misalignment. The glass is completely sealed from the atmosphere, so owners very rarely need to clean it. The tube is completely closed off, so the telescope is not vulnerable to temperatures. This causes the telescope to produce sharper images than a reflector with the same size.

Inaccuracy

• The image produced by the refractor telescope is not completely accurate because of chromatic aberration, which results from the nature of the wavelengths that create color. Longer wavelengths, which produce red colors, are bent less than shorter wavelengths, which produce blue colors. This distorts the colors viewed through a telescope. Compensating lenses counteract some of the chromatic aberration. Very long objective focal lengths also reduce this problem.

Problems with Lens

• Ultraviolet light does not pass through a refractor lens. Thicker lenses do not allow as much light through. Manufacturers struggle to create perfect glass lenses that can accurately bend light. Another problem has to do with the weight of the lens. Only the ends of the lens can support the lens. The lens will sag under its own weight. The glass on a refracting telescope is thicker in the center and becomes thinner towards the edges.