Most department store telescopes are refractors. A refractor has a large glass lens at the front end, usually two or three inches across. You can also find reflecting telescopes or reflectors in department stores. A reflector has a large mirror, usually between 3 and 10 inches, mounted in the bottom of the tube. Reflectors typically cost less than refractors, because mirrors are cheaper to make than lenses. So the reflector is a better buy; you can get a larger, or wider telescope for the same money. And the wider the mirror, the more light it can gather, which means more magnification. A good rule of thumb is fifty power for every inch of aperture. If a scope has only a three-inch lens or mirror, then you really should only expect it to magnify up to about a hundred and fifty power – after that, the image looks dim and fuzzy. Buy a reflector that has a mirror at least four inches to six inches across. That will give you the ability to magnify images up to 200 power or more.