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Webster 1913 Edition
Aplanatic
Apˊla-nat′ic
,Adj.
[Gr.
ἀ
priv. + [GREEK] disposed to wander, wandering, [GREEK] to wander.] (Opt.)
Having two or more parts of different curvatures, so combined as to remove spherical aberration; – said of a lens.
Aplanatic focus
of a lens (Opt.)
, the point or focus from which rays diverging pass the lens without spherical aberration. In certain forms of lenses there are two such foci; and it is by taking advantage of this fact that the best aplanatic object glasses of microscopes are constructed.
Webster 1828 Edition
Aplanatic
APLANAT'IC
,Adj.
An aplanatic telescope is one which entirely corrects the aberration of the rays of light. It is thus distinguished from the achromatic, which only partially corrects the aberration.