Design A telescope that uses a curved mirror or combinations of curved mirrors, to gather and concentrate light, is called a Reflecting Telescope . A telescope that uses a curved lens or combinations of curved lenses, to gather and concentrate light, is called a Refracting Telescope . Each design allows light to be focused at a point to form an image . Most widely used modern telescopes are reflecting. The absorption of the light by the glass lens.
Large lenses are quite heavy and can sage under their own weight.
Lenses have two surfaces that must be cut and polished. Currently, professionals do no direct optical viewing. Spectroscopy, the study of spectral lines, is still one of the more widely used telescopic methods. A good observatory needs to have clear, dry, dark, and smooth air, as well as to be located at a low latitude It is also best to have international cooperation . The time that is required to view a section of space is greatly reduced by having a larger telescope area.