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Glossary

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T

  • telescope - Galilean

    A type of refracting telescope in which eye-lens is divergent (concave), giving an erect image. It is short than an astronomical telescope equal magnifying power

  • telescope - Gregorian

    Telescope consisting of two concave mirrors; the primary mirror (a concave paraboloid) collects the light and brings it to a focus before the secondary mirror (a concave ellipsoid) where it is reflected back through a hole in the centre of the primary, and thence out the bottom end of the instrument where it can be viewed with the aid of the eyepiece.

  • telescope - Newtonian

    The Newtonian telescope is a type of reflecting telescope invented by the British scientist Sir Isaac Newton (1643-1727), using a concave primary mirror and a flat diagonal secondary mirror. He first constructed it in 1669

  • telescope - reflecting

    A reflecting telescope (also called a reflector) is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image.

  • telescope - refracting

    A refracting or refractor telescope is a dioptric telescope that uses a lens as its objective to form an enlarged image.

  • telescope - Schmidt Cassegrain

    A type of catadioptric telescope that combines a folded optical path with a corrector plate to make a compact astronomical instrument. As in the Schmidt camera it uses a spherical primary mirror and a Schmidt corrector plate to correct for spherical aberration. From the Cassegrain, it inherits the convex secondary mirror, perforated primary mirror, and a final focal plane located behind the primary.

  • telescope - sighting

    A refracting telescope with an index or graticule used for sighting guns.

  • television camera

    A high-end device for recording electronic moving images (as opposed to a movie camera, that records the images on film).

  • television receiver

    Devices that convert incoming television signals into the original images and their associated sounds.

  • tellurometer

    A type of rangefinder employing microwaves (frequency modulated) to measure distances by timing reflected beamed signels.

  • tenaculum

    An instrument consisting of a fine, sharp hook attached to a handle, and used mainly for taking up arteries, and the like

  • tensometer

    A device used to evealuate how much a substance stretches under stress.

  • tent - portable building

    Collapsible shelter of canvas, skin, plastic, or other flexible and water-repellent material stretched and sustained by poles, usually secured by ropes to pegs in the ground.

  • terminal illness

    An advanced stage of a disease that has no known cure and is fatal.

  • terra sigillata

    A form of clay from the Greek islands of Lemnos or Samos. Until the 1700s, terra sigillata was used as a medicine and seen as a general cure for bodily impurities.

  • terrestrial globe

    Refers to spheres that bear a map of the Earth on their surface. They were first devised by the ancient Greeks, who had calculated that the Earth is a sphere. Modern terrestrial globes are typically mounted on an axle that permits rotation and is tilted 23.5 degrees from the vertical in order to simulate the inclination of the Earth relative to the plane in which it orbits the Sun.

  • terrestrial telescope

    Type of telescope, an optical instrument that produces a magnified image of distant view, which gives an upright image in the eyepiece. These are usually refracting telescopes, often of the Galilean optical design with three or more draw tubes for compact storage, typically used in the field. They can include catadiotric or othe reflecting designs.

  • test topic

    test term

  • test tube

    Hollow cylinders of thin glass with one end closed. Test tubes are used for chemical and biological experiments and analysis.

  • testimonial

    Documents containing affirmation of person's character or the value of a thing. Specifically, written declarations stating an individual's achievements or the usefulness of a product or service, such as a letter of endorsement.

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