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Zach AST ch. 1-5 Voc

achromatic Lens A telescope lens composed of two lenses ground from different kinds of glass and designed to bring two selected colors to the same focus and correct for chromatic aberration.
active optics Thin telescope mirrors that are controlled by computers to maintain proper shape as the telescope moves.
adaptive optics A computer-controlled optical system in an astronomical telescope used to partially correct for seeing.
angular distance The angle formed by lines extending from the observer to two locations.
angular diameter The angel formed by lines extending from the observer to opposite sides of an object.
apogee The point farthest from the Earth in the orbit of a body circling Earth.
array detector A grid of photosensitive detectors for the purpose of recording images. Commercial still and video digital cameras contain CCD array detectors. See also "charge coupled device"
asterism A named grouping of stars that is not one of the recognized constellations. Examples are the Big Dipper and the Pleiades.
Cassegrain focus The optical design in which the secondary mirror reflects light back down the tube through a hole in the center of the objective mirror.
charge-coupled device (CCD) An electronic device consisting of a large array of light-sensitive elements used to record very faint images.
chromatic abberation A distortion found in refracting telescopes because lenses focus different colors at slightly different distances. Images are consequently surrounded by color fringes.
deferent In the Ptolemaic theory, the large circle around Earth along which the center of the epicycle was thought to move.
eccentricity, e A number between 1 and 0 that describes the shape of an ellipse; the distance from one focus to the center of the ellipse divided by the semimajor axis.
epicycle The small circle followed by a planet in their Ptolemaic theory. The center of the epicycle follows a larger circle (the deferent) around Earth.
equant In the Ptolemaic theory, the point off-center in the deferent from which the center of the epicycle appears to move uniformly.
grating A piece of material in which numerous microscopic parallel lines are scribed. Light encountering a grating is dispersed to forms a spectrum.
interferometry The observing technique in which separated telescopes combine to produce a virtual telescope with the resolution of a much larger-diamter telescope.
neap tide Ocean tide of low amplitude occurring at first- and third-quarter moon.
node The point where an object's orbit passes through the plane of Earth's orbit.
magnitude scale The astronomical brightness scale. The larger the number, the fainter the star.
parallax The apparent change in position of an object due to a change in the location of the observer. Astronomical parallax is measured in seconds of arc.
photographic plate An old-fashioned means of recording astronomical images and photometric information on a photographic emulsion coating a glass plate. See also "array detector" and "charge-coupled device"
photon A quantum of electromagnetic energy that carries an amount of energy that depends inversely on its wavelength.
polarity Orientation and strength of a magnetic field's manifestation as north and south poles. Also applies to an electrical field's manifestation as positive and negative charges.
precession The slow change in the direction of Earth's axis of rotation. One cycle takes nearly 26,000 years.
primary lens In a refractice telescope, the largest lens.
reflecting telescope A telescope that uses a concave mirror to focus light into an image.
refracting telescope A telescope that forms images by bending (refracting) light with a lens.
resolving power The ability of a telecope to reveal fine detail. Depends on the diameter of the telescope objective.
retrograde motion The apparent backward (west-ward) motion of planents as seen against the background of stars.
spectrograph A device that seperates light by wavelengths to produce a spectrum.
spring tide Ocean tide of high amplitude that occurs at full and new moon.
synodic period The time a soloar system body takes to orbit the sun once and return to the same orbital relationship with Earth; that is, orbital period referenced to Earth.
wavelength The distance between successive peaks or troughs of a wave, usually represented by ___.
Created by: takeshertime