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Zach AST ch. 1-5 Voc
| Question | Answer |
|---|---|
| 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
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