Early Designs
Despite the fact that the Cooke design was patented in 1893 it seems that the use of achromatic triplet designs in astronomy appeared as early as 1765. The 1911 Encyclopædia Britannica wrote:
- The triple object-glass, consisting of a combination of two convex lenses of crown glass with a concave flint lens between them, was introduced in 1765 by Peter, son of, John Dollond, and many excellent telescopes of this kind were made by him.
This parallels the fact that John Dollond had in turn patented the achromatic doublet in the 1750s, though it had been used decades earlier.
Read more about this topic: Cooke Triplet
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