What types of telescopes are available ?
There are many types of telescope available with each having its own unique advantages and disadvantages. The three most common types are the Refractor, the Newtonian Reflector and the Schmidt-Cassegrain.
Refractors use lenses to collect and focus light to an eyepiece located at the back of a tube. They provide the sharpest images but tend to be limited to small sizes due to cost. A common problem with this design is a noticeable blue colour around bright objects. This type of telescope is most frequently chosen for viewing the planets.
Newtonian Reflectors use a curved mirror at the bottom of a tube, which reflects light back to a small, flat mirror positioned at a 45 degree angle which deflects the light to an eyepiece at the side of the tube. They provide the brightest images for the money. Short focal length reflectors can have image distortion at the edges of the field. This may be compensated for with the use of better eyepiece designs.
Schmidt-Cassegrain telescopes have a special front lens called a corrector plate combined with mirrors like the reflector. Instead of sending the light to the side of the tube like the reflector, the smaller mirror is curved and sends the light to the eyepiece at the back end of the telescope. These telescopes are the most compact. This type of telescope is frequently chosen for photography. Schmidt-Cassegrains are most often associated with computer assisted location of objects.
Developed by Stewart Attlesey