Optical Telescope
The telescope is an important astronomical tool that gathers and focuses electromagnetic radiation. Telescopes serve to both increase the angular size and the brightness of objects. When we speak about telescopes we are usually referring to optical telescopes, but many other types of telescopes also exist for other spectrum of electromagnetic radiation. It is unclear as to who it was that actually invented the telescope but Galileo Galilei is credited as being the first to use a telescope for astronomical purposes in 1609. Most people believe that the only thing a telescope does is magnify images. The problem is that the more you magnify an image the darker and blurrier it will become. For this reason, a telescope must also brighten and clear up an image in order to be useful. Telescopes have three basic functions. The first, and most important function of a telescope, is to gather light. By gathering light a telescope is able to make feint objects brighter and to make objects visible that are so feint that they are not visible to the human eye without a telescope. The telescope collects the light and concentrates it at a focus, the difference between the brightness when viewed through a telescope and the brightness as seen by the human eye is the telescopes light-gathering power. In general, the larger a telescope is the more light it will be able to gather, and the brighter objects will appear (How Does a Telescope Work?). The second function of a telescope is to resolve fine detail, also known as angular resolution. Angular resolution refers to the telescope 's ability to make objects in the heavens appear sharper and to separate objects that are close together in the sky. Angular resolution is usually expressed in terms of the minimum angle between two points that can be clearly separated. If the resolution of a telescope is greater than the angular separation of two stars it will be possible to view two separate and distinct objects. If the
Cited: "Catadioptric Telescopes." Northern Stars Planetarium. 20 Mar. 2005. http://www.northern-stars.com/catadioptric_telescopes.htm "History of telescopes." Wikepedia. 20 Mar. 2005. http://en.wikipedia.org/wiki/History_of_telescopes "How Does a Telescope Work?" Stardust. 21 Mar. 2005. http://www.stardustgallery.com/page9.htm. "It Takes More than One Type of Telescope to See the Light." Science@Nasa. 21 Mar. 2005. http://science.nasa.gov/newhome/headlines/features/ast20apr99_1.htm "Telescopes." Telescopes and Astronomy. 21 Mar. 2005. http://www.telescopes-astronomy.com.au/