telescope


Also found in: Dictionary, Thesaurus, Legal, Acronyms, Idioms, Encyclopedia, Wikipedia.

tel·e·scope

(tel'ĕ-skōp),
1. An optic instrument used to visualize or photograph distant or out-of-view objects through magnification of the image or angulation of the reflected light. In medicine, usually combined with endoscopy.
2. Enclosure such that smaller segments collapse into larger.
[tele- + G. skopeō, to view]

telescope 

An optical instrument for magnifying the apparent size of distant objects. It consists, in principle, of two lenses: (1) the objective, being a positive lens which forms a real inverted image of the distant object; (2) the eyepiece through which the observer views a magnified image of that formed by the objective. The eyepiece may be either positive (astronomical or Kepler telescope) or negative (galilean telescope). The magnification M of a telescope is given by the following formula
M = fo/fe
= Do/Dewhere fo is the second focal length of the objective, fe the first focal length of the eyepiece, and Do and De are the diameters of the entrance and exit pupils of the telescope (approximately equal to the diameters of the objective lens and the eyepiece).There are also some telescopes that do not use a lens (or lens system) as objective, as these are difficult to produce if large apertures and minimum aberrations are required. These telescopes use a concave mirror (usually parabolic) as the objective. They are called reflecting telescopes. Light from a distant object is collected by the large concave mirror and reflected onto a small mirror (positive in the Cassegrain telescope and negative in the gregorian telescope). This mirror is located on the optical axis and light is then transmitted through a central hole in the concave mirror onto the eyepiece. In the newtonian telescope the light collected by the large concave mirror is reflected onto a small plane mirror at a 45º angle to the optical axis, and transmitted to the eyepiece, which is at right angles to the optical axis (Fig. T1). See binoculars; eyepiece; telescopic magnification; objective.
astronomical telescope See telescope.
bioptic telescope A system of lenses forming a galilean or Kepler telescope which is mounted high on a plastic spectacle or carrier lens with the distance correction, so as to allow the patient to look through either the telescope, or below, by moving his or her head. It is used to magnify distant objects for patients with low vision. Syn. bioptic position telescope.
Cassegrain telescope See telescope.
Dutch telescope See galilean telescope.
galilean telescope A simple optical system that allows observation of far objects with a low magnification and without image inversion. It consists of a convex lens, which acts as the objective, and a concave lens as the eyepiece. Magnification of such a telescope rarely exceeds ✕ 5. This optical system is used in opera glasses and as a low vision aid (Fig. T1). Syn. Dutch telescope. See binoculars; minification.
gregorian telescope; Kepler telescope; newtonian telescope See telescope.
reflecting telescope A telescope that uses a concave mirror as the objective.
refracting telescope A telescope that uses a positive lens system as the objective.
reverse telescope See visual expander field.
terrestrial telescope A telescope that provides an erect image of a distant object. The image is usually erected by means of a lens system placed between the objective and the eyepiece. It does, however, make the terrestrial telescope relatively longer than an astronomical telescope. See binoculars; erector.
Fig. T1 Telescopes: A, galilean; B, Keplerenlarge picture
Fig. T1 Telescopes: A, galilean; B, Kepler
References in periodicals archive ?
If these planets have atmospheres, the James Webb Space Telescope will be the key to unlocking their secrets," NASA exoplanet program scientist Doug Hudgins has (https://www.
Aldrich got the idea for the library telescope program from the New Hampshire Astronomical Society, which has placed more than 80 telescopes in public libraries in central and southern New Hampshire since it began its program in December 2008.
A second telescope will be installed at the McDonald Observatory before the end of the year.
One telescope, working alone, may occasionally malfunction and incorrectly detect an asteroid.
The district is doing the telescope project in conjunction with the Lawrence Hall of Science at the University of California at Berkeley.
Access would be through a Web site where people could download his own software that would enable people to control the telescope and obtain whatever images or data they required.
Chile is at the center of the greatest construction program ever undertaken in ground-based astronomy," says Smith, director of the Cerro Tololo Inter-American Observatory home to one of the world's most-touted optical telescopes.
To a twentieth-century perspective, connecting reading to the cognitive and philosophical problems associated with the telescope may seem arbitrary.
The Very Large Array (VLA) radio telescope near Sorroro, N.
He began a program here at the telescope in 1966 to follow 100 stars, month after month, year after year.
The first is the irony of the Vatican building its telescope after Pope John Paul II visited the Southwest in 1986 and urged American Indians to fight for land rights.