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Achromatic Doublet Refractors

Achromatic doublet refractor telescopes use an achromatic lens that is designed to limit the effects of chromatic and spherical aberration.

The achromatic lens is made with two glass types (crown and flint) with different dispersion:

  • Crown glass - convex lens with relatively low dispersion
  • Flint glass - concave lens with relatively high dispersion

Achromatic lenses are corrected to bring two wavelengths (red and blue) into focus in the same plane.

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