An achromatic refracting telescope uses an achromatic objective lens to correct for chromatic aberration. It consists of a pair of diverging and converging lenses that bring light of two different wavelengths (usually red and blue light) to focus at the same point.

The consequence is a dramatic reduction in the amount of false colour that results from using a single lens.

Lick Observatory's 91-centimeter (36-inch) refracting telescope (San Jose, California, USA)

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Sky Highlights - April 2017

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