Achromatic telescope with two eyepieces

London P&J Dollond, 1750 - 1774

This is an achromatic telescope. A telescope is achromatic (= colourless) if the lens system in the telescope makes all colours of the incident light travel the same path. Until the middle of the eighteenth century, the image of a lens telescope (refractor) was not sharp. This was caused by chromatic dispersion: the lenses refracted the light unevenly, which resulted in a blurred image with coloured edges. In 1758, the English John Dollond came with the idea to use two different kinds of glass, each with a different refractive index. By adjusting the shape and the kind of glass of the lenses, they counteracted the prismatic effect of each other. Dollond's invention meant a breakthrough in the development of the telescope. One hundred and fifty years after the invention of the first telescope, there was finally a successful solution to the problem of chromatic dispersion in lens telescopes.

Administration name

Fysisch Kabinet


Achromatic telescope with two eyepieces

Translated title

Achromatic telescope with two eyepieces


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[{'start': '1750', 'end_precision': u'', 'end': '1774', 'start_precision': u''}]


[{'material': 'Glass'}, {'material': 'Mahogany'}, {'material': 'brass'}]

Object number

FK 0354

Reproduction reference

[{'reference': '..\\images\\Fysisch\\Gekoppelde afbeeldingen\\FK 0354.jpg'}]