Generally there can be found three fundamental types of telescopes:
1-) Refractors : They are used to observe moon and the planets. They are thin and long in shape and collect the light through multi element lenses.
2-) Reflectors: They are used to observe both planet and deep sky. Collect the light through concave mirror.
3-) Catadioptrics: They are used to observe Moon, Planets, Deep Sky including clusters, galaxies, nebulas and comets. They collect the light through both lenses and mirrors.
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