A reflecting telescope (also called a reflector) is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century, by Isaac Newton, as an alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic aberration. Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for very large diameter objectives. Almost all of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in many design variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is sometimes referred to as a “catoptric” telescope.
A great choice if you are on a small budget or indeed looking for large aperture telescopes. These are sensitive to movement and do require regular collimation to ensure the optical pathways remain perfectly aligned. John Dobson took a reflecting telescope and placed it on a very simple base to make a Dobsonian reflecting telescope which are very popular amongst amateurs and those wishing to see the faintest of objects.