Each side of each piece is ground and polished, and then the two pieces are assembled together. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus in the same plane.

Chester More Hall is noted as having made the first twin color corrected lens in 1730.

Dollond achromats were quite popular in the 18th century. A major appeal was they could be made shorter. However, problems with glass making meant that the glass objectives

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