Do i need a special type of mirror to build my own telescope?
Barry, It would be nice if a shaving mirror were a good shortcut for a telescope, but the quality is just not there! Here are some things to understand, and you will see why: An astronomical telescope has to focus *all* light coming from a particular point in space (like a star or a single spot on the moon) to a single point at the eyepiece of your telescope. This is generally done with a system of mirrors, lenses, or both to make up your telescope. The simplest type of mirror telescope (sometimes called a “Newtonian,” as Isaac Newton described the optics and built several of these) consists of a single curved mirror to focus the light to a point, and a smaller flat mirror to bring the focused light outside the telescope tube to an eyepiece, where it is focused for your eye. A Newtonian scope uses a mirror shaped as a parabola (usually by grinding high-quality glass flats, and coated on the parabolic surface – the *front* surface of the mirror. The parabolic shape is required to bring
