Planetary aberration

Aberration \Ab`er*ra"tion\, n. [L. aberratio: cf. F. aberration.
   See {Aberrate}.]
   1. The act of wandering; deviation, especially from truth or
      moral rectitude, from the natural state, or from a type.
      "The aberration of youth." --Hall. "Aberrations from
      theory." --Burke.
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   2. A partial alienation of reason. "Occasional aberrations of
      intellect." --Lingard.
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            Whims, which at first are the aberrations of a
            single brain, pass with heat into epidemic form.
                                                  --I. Taylor.
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   3. (Astron.) A small periodical change of position in the
      stars and other heavenly bodies, due to the combined
      effect of the motion of light and the motion of the
      observer; called {annual aberration}, when the observer's
      motion is that of the earth in its orbit, and daily or
      {diurnal aberration}, when of the earth on its axis;
      amounting when greatest, in the former case, to 20.4'',
      and in the latter, to 0.3''. {Planetary aberration} is
      that due to the motion of light and the motion of the
      planet relative to the earth.
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   4. (Opt.) The convergence to different foci, by a lens or
      mirror, of rays of light emanating from one and the same
      point, or the deviation of such rays from a single focus;
      called {spherical aberration}, when due to the spherical
      form of the lens or mirror, such form giving different
      foci for central and marginal rays; and {chromatic
      aberration}, when due to different refrangibilities of the
      colored rays of the spectrum, those of each color having a
      distinct focus.
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   5. (Physiol.) The passage of blood or other fluid into parts
      not appropriate for it.
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   6. (Law) The producing of an unintended effect by the
      glancing of an instrument, as when a shot intended for A
      glances and strikes B.
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   Syn: Insanity; lunacy; madness; derangement; alienation;
        mania; dementia; hallucination; illusion; delusion. See
        {Insanity}.
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