Từ vựng về Astronomy

 
 
  • APPARENT FIELD OF VIEW: The size in degrees of the field as seen through the eyepiece of your telescope.
  • APERTURE: The diameter of the main light gathering element in a telescope.
  • ASTERISM: A grouping of stars resembling a familiar shape.
  • ASTIGMATISM: A defect in optics in which a lens or mirror has two different amounts of curvature at 90 degrees to each other.
  • CATADIOPTRIC TELESCOPE: A telescope using both mirrors and lenses to focus light. The most popular of these is the Schmidt-Cassegrain telescope.
  • CELESTIAL SPHERE: The imaginary sphere on which the the night sky is seen to be projected on.
  • CHROMATIC ABERRATION: The discoloration of a bright object caused by dispersion in a refracting telescope's objective lens(es). This dispersion causes different colors of light to come to a focus at different distances.
  • CIRCUMPOLAR: Star or objects that are close enough to the pole so that they never set from your particular latitude.
  • COLLIMATION: The systematic aligning of optical elements in a telescope to emsure the brightest and sharpest views possible.
  • COMA: A defect causing stars to be deformed into a fanlike or comet shape. This is typically caused by misaligned optics.
  • DECLINATION: The celestial equivalent of latitude. Declination is measured from the celestial equator to the celestial pole, spanning 90 degrees.
  • DIFFRACTION-LIMITED: A term used by telescope manufacturers to represent the 1/4-wavelength Rayleigh limit of optics. This represents an error where the amount of detail seen is limited only by the wave nature of light. Errors greater than this result in optics that degrade sharply.
  • DOUBLE-STAR: Two stars close together so that they appear as one at lower magnifications. Many of these stars are actually associated with each other gravitationally forming a binary system.
  • ECLIPTIC: The path in the sky the sun follows.
  • EXIT PUPIL: The diameter of the cone of light exiting the eyepiece. This can be calculated by dividing the diameter of the objective by the magnification used.
  • FOCAL LENGTH: The distance from the objective lens or mirror to the point where the light converges, the focal point. This distance is usually measures in millimeters.
  • FOCAL RATIO: The ratio of the focal length divided by the diameter of the primary mirror or lens.
  • GLOBULAR CLUSTER: An enourmous grouping of 25,000 to upwards of over 100,000 old stars. Globular clusters are gravitationally held together and orbit the outer reaches of most, if not all, galaxies.
  • LIMITING MAGNITUDE: The magnitude of the dimmest object which can be seen using a telescope of a given aperture or with your naked eye.
  • MAGNIFICATION: The amount of increase in apparent size of an object. This quantity can be derived by dividing the telescope focal length by the eyepiece focal length.
  • MAGNITUDE: A scale used to compare the brightness of objects in the sky. One magnitude is a difference of 2.512 times in brightness.
  • MESSIER OBJECT: Any of the 110 objects catalogued by French astronomer Charles Messier in the late 18th century. Messier was a comet hunter and catalogued these as objects to "avoid," or objects that could be easily mistaken as a comet. They include many of the best nebulae, star clusters, and galaxies that are visible from mid-northern latitudes.
  • NEBULA: A large cloud of gas and dust in space. Most are dark and obscure the light from background stars. Others glow brilliantly from the energy of hot star within them.
  • OPEN CLUSTER: A loose grouping of relativly young star grvitationally bound together. Most stars in open clusters formed as a group inside large nebulae.
  • OPPOSITION: The point in time when a planetary body is at the same heliocentric longitude as the Earth. Bodies at opposition rise at sunset.
  • PLANETARY NEBULA: The last gasp of a dying star, a planetary nebula consists of the outer layers of a star. These layers glow brilliantly from the hot ultraviolet radiation from the stellar core in the middle.
  • REFLECTING TELESCOPE: A telescope which uses mirrors to gather and focus light.
  • REFRACTING TELESCOPE: A telescope which uses lenses to gather and focus light.
  • RIGHT ASCENSION: The astronomical equivalent of longitude. It starts where the ecliptic intersects the celestial equator in Pisces and moves through 24 hours.
  • SEEING: A rating of how steady the atmosphere is at your observing site. Most astronomers use a scale of 1-10 or 1-5. Cold clear nights typically have the worst seeing. The better the seeing, the better high power views of the planets and double stars.
  • SPHERICAL ABERRATION: The departure of a wavefront of foucused light from a spherical shape.
  • TRANSPARENCY: A rating of how clear the night sky is. This is usually given by the magnitude of the faintest star easily visible to the naked eye. Cold clear nights have some the best transparency.
  • TRUE FIELD OF VIEW: The size of the actual area of the sky you are viewing measured in degrees. This quantity can be approzimated by dividing the apparant field of the eyepiece by the magnification.
  • ZENITH: The point in the celestial hemisphere that is directly above you or your observing location.