Types of Telescopes
Any particular telescope will fall into one of two classes: refractor or reflector. A refractor employs a lens as its objective. A reflector’s objective is a magnifying mirror. It is easy to remember which is which by simply remembering that mirrors reflect light, thus the name reflector for mirror based telescopes. The big lens in a refractor bends light, (in other words refracts light) in a manner similar to a prism.
Figure 2: Light from a star is focused to a point.
At this point you should know that individual stars in the night sky are so far away that no amount of magnification on the largest telescope in the world can make them appear to be bigger than a dot! However, planets and the moon can be magnified because they are much closer than the stars. Also, there are zillions of objects that are as far or farther away than the stars which are so huge that magnification does make them bigger. Figure 2 illustrates how a lens or mirror concentrates incoming starlight.
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