align a telescope
âxatidan-e durbin, ~ teleskop
Fr.: aligner un télescope
Setting the axis of a telescope parallel to prime directions. In equatorial mounting, they are made parallel with the Earth's axis of rotation and the equator respectively. → collimation.
automatic photometric telescope
durbin-e šidsanjik-e xodkâr, teleskop-e ~ ~
Fr.: télescope photométrique automatique
A telescope developed to perform photometric observations automatically.
durbin-e bâlon-bord, teleskop-e ~
Fr.: télescope porté par ballon
A remotely guided or automatic telescope carried to high altitudes by a balloon.
→ balloon astronomy; borne "a past participle of bear," from O.E. beran "bear, bring, wear," from P.Gmc. *beranan (O.H.G. beran, Goth. bairan "to carry"), from PIE root *bher-; "to carry;" compare with Av./O.Pers. bar- "to bear, carry," bareθre "to bear (infinitive)," bareθri "a female that bears (children), a mother," Mod.Pers. bordan "to carry," Skt. bharati "he carries," Gk. pherein, L. fero "to carry." → telescope.
durbin Cassegrain, teleskop-e ~ (#)
Fr.: Télecope Cassegrain
A reflecting telescope whose primary mirror has a hole bored through the center to allow the reflected light from the convex secondary mirror be focused beyond the back end of the tube.
Cassegrain, named after the French priest and school teacher Laurent Cassegrain (1629-1693), who invented this system in 1672; → telescope.
Fermi Gamma-ray Space Telescope
Durbin-e fazâyi-ye partowhâ-ye gâmâ Fermi
Fr.: Télescope spatial à rayons gamma Fermi
A space observatory, formerly named GLAST, devoted to the study of → gamma rays emitted from astrophysical objects. Developed by NASA in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the United States, Fermi was launched on June 11, 2008. The main instrument, the Large Area Telescope (LAT), is an imaging → camera covering the energy range from about 20 → MeV to more than 300 → GeV. Such gamma rays are emitted only in the most extreme conditions, by particles moving very nearly at the → speed of light. The LAT's → field of view covers about 20% of the sky at any time, and it scans continuously, covering the whole sky every three hours. Another instrument, the Gamma-ray Burst Monitor (GBM) has a field of view several times larger than the LAT and provides → spectral coverage of → gamma-ray burst that extends from the lower limit of the LAT down to 10 → keV.
Five-hundred-meter Aperture Spherical radio Telescope (FAST)
The 500 m diameter → radio telescope which is the largest → single-dish antenna in the world. It is an Arecibo type telescope nestled within a natural basin in China's remote and mountainous Dawodang, Kedu Town, in southeastern China's Guizhou Province. The → reflector consists of 4,450 triangular panels, each with a side length of 11 m. More than 2,000 → actuators are used, according to the feedback from the measuring system, to deform the whole reflector surface and directly correct for → spherical aberration. Several detectors are used to cover a frequency range of 70 MHz to 3 GHz.
teleskop bâ fotâd-e barmažandé
Fr.: télescope à incidence rasante
A telescope design used for focusing → extreme ultraviolet, → X-rays, and → gamma rays. Such short wavelengths do not reflect in the same manner as at the large incidence angles employed in optical and radio telescopes. Instead, they are mostly absorbed. To bring X-rays to a → focus, one has to use a different approach from → Cassegrain or other typical → reflecting telescopes. In a grazing-incidence telescope, incoming light is almost → parallel to the → mirror surface and strikes the mirror → surface at a very → shallow angle. Much like skipping a stone on the water by throwing it at a low angle to the surface, X-rays may be → deflected by mirrors arranged at low incidence angles to the incoming energy. Several designs of grazing-incidence mirrors have been used in various → X-ray telescopes, including → plane mirrors or combinations of → parabolic and → hyperbolic surfaces. To increase the collecting area a number of mirror elements are often nested inside one another. For example, the → Chandra X-ray Observatory uses two sets of four nested grazing-incidence mirrors to bring X-ray photons to focus onto two → detector instruments. → Bragg's law; → X-ray astronomy.
durbin-e Gregori, teleskop-e ~ (#)
Fr.: télescope de Gregory
A reflecting telescope in which the light rays are reflected from the primary mirror to a concave secondary mirror, from which the light is reflected back to the primary mirror and through the central hole behind the primary mirror. Compare with the → Cassegrain telescope, in which the secondary mirror is convex.
Named after the Scottish mathematician and astronomer James Gregory (1638-1675), who devised the telescope, but did not succeed in constructing it; → telescope.
Fr.: lunette de guidage
A telescope which is attached to a second telescope being used for photographic purposes. The guiding telescope, mounted parallel to the optical axis of the main telescope, is used by the observer to keep the image of a celestial body motionless on a photographic plate.
Hubble Space Telescope (HST)
durbin-e fazâyi-ye Hubble, teleskop-e ~ ~ (#)
Fr.: télescope spatial de Hubble
A telescope of 2.4 m in diameter, a joint NASA and ESA project, launched in 1990 into a low-Earth orbit 600 km above the ground. It was equipped with a collection of several science instruments that worked across the entire optical spectrum (from infrared, through the visible, to ultraviolet light). During its lifetime Hubble has become one of the most important science projects ever.
durbin-e forusorx (#), teleskop-e ~ (#)
Fr.: télescope infrarouge
A telescope capable of observing → infrared radiation from astronomical objects.
James Webb Space Telescope (JWST)
durbin-e fazâyi-ye James Webb, teleskop ~ ~ ~
Fr.: Télescope spatial James Webb
A large, infrared space telescope with a mirror 6.55 m in diameter, scheduled for launch in 2018. JWST's instruments will work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range (0.6 to 28 μm). The scheduled instruments are Near IR Camera (NIRCam, field of 2.2 x 4.4 arcmin, wavelength range 0.6-5 μm), Near IR Spectrograph (NIRSpec, 3.5 x 3.5 arcmin, 0.6-5 μm, resolving powers of ~ 100, ~1000, and ~3000), Mid IR Instrument (MIRI, 1.4 x 1.9 arcmin, 5-27 μm, R ~ 3000), and Fine Guidance Sensor (FGS, 2.3 x 2.3 arcmin, 0.6-5 μm, R ~ 100). The successor to the → Hubble Space Telescope will be placed in an orbit about 1.5 million km from the Earth, at the → Lagrangian point L2. The JWST project is a → NASA-led international collaboration with the → European Space Agency and the Canadian Space Agency. The scientific goals of JWST can be grouped under four broad topics: first light after the Big Bang; galaxy formation; birth of stars and protoplanetary systems; and planetary systems and the origins of life.
Named in honor of James E. Webb (1906-1992), who headed NASA from 1961 to 1968, overseeing all the manned launches in the Mercury through Gemini programs, until before the first manned Apollo flight; → space; → telescope.
durbin-e Kepler, teleskop-e ~ (#)
Fr.: télescope de Kepler
A → refracting telescope which has simple → convex lenses for both → objective and → eyepiece. It suffers from → chromatic aberration, which can be reduced by increasing the → focal ratio. It was first devised by Kepler in 1615.
durbin-e Maksutof, teleskop-e ~ (#)
Fr.: télescope de Maksutov
A → reflecting telescope incorporating a deeply curved → meniscus, → lens, which corrects the → optical aberrations of the spherical → primary mirror to give high-quality → images over a wide → field of view.
Named for the Russian optical specialist Dmitri Maksutov (1896-1964), who developed the design; → telescope.
durbin-e Newton, teleskop-e ~
Fr.: télescope de Newton, ~ newtonien
A telescope with a concave paraboloidal objective mirror and a small plane mirror that reflects rays from the primary mirror laterally outside the tube where the image is viewed with an eyepiece.
râdio-teleskop (#), teleskop-e râdioyi (#)
Fr.: radio télescope
A telescope whose receiver is sensitive to → radio waves.
teleskop-e bâztâbi (#), durbin-e ~ (#)
Fr.: télescope réflecteur
A telescope in which the image is produced by reflection of light by a concave mirror.
teleskop-e šekasti (#), durbin-e ~ (#)
Fr.: lunette astronomique
A telescope in which an image is formed by the refraction of light through a lens or lens system.
teleskop-e Ritchey-Chrétien, durbin-e ~
Fr.: télescope Ritchey-Chrétien
A type of → Cassegrain telescope in which the → primary mirror is a → hyperboloid. It is designed to eliminate → coma and → spherical aberration, thus providing a relatively large field of view as compared to a more conventional configuration.
Named after the American astronomer George Ritchey (1864-1945) and the French optician Henri Chrétien (1879-1956); → telescope.
teleskop-e Schmidt, durbin-e ~ (#)
Fr.: télescope de Schmidt
A telescope with a spherical concave primary mirror in which the aberration produced by the spherical mirror is compensated for by a thin correcting lens placed at the opening of the telescope tube. Its very wide-field performance makes it suitable for surveys.
Named after Bernhard Woldemar Schmidt (1879-1935), a German optician of Estonian origin, who invented the telescope in 1930; → telescope.