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The reflector telescope (also referred to as a Newtonian after the astronomer Sir Isaac Newton) is the most common type of large-aperture telescope. It is the cheapest telescope per inch of aperature but some observors do not like the partial obstruction which holds and includes the 'secondary' mirror. Folks who look at the planets usually will not use a Reflector. A reflector focuses light by using mirrors. It is essentially a hollow tube with a large mirror at one end and a smaller mirror at the other end. The smaller mirror reflects the image through an eyepiece located on the side of the tube. Since reflectors do not contain glass lenses, they are lightweight and inexpensive to manufacture. This simple design provides tremendous light-collecting capability at low costs. Reflectors are the least expensive type of telescope per aperture size. They are also quite easy to make. Many amateur astronomers consider making their own telescope as somewhat as a rite of passage. Although they are not as good as refractors for planetary observing, reflectors are ideal for observing faint deep-sky objects such as nebulae and galaxies. The mirrors require frequent alignment for optimal viewing, but can easily be adjusted. Since they have no glass lens on the front of the tube, reflectors are not as susceptible to dew as other telescopes. They can be used on both the equatorial mount as well as the Dobsonian mount. Due to their low cost, Newtonian reflectors are a good choice for someone just starting out in astronomy.