Dollond’s Achromatic Twin Telescopes. Failed projects of the Dutch philosopher Frans Hemsterhuis (1721–1790) and the English astronomer William Rutter Dawes (1799–1868)

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Frans Hemsterhuis is best known as an important Dutch philosopher. But he had also a profound interest in astronomy and optics. In the late 1760s Hemsterhuis developed the ambition to improve the telescope, so that astronomers would be able to witness more celestial objects in the night sky. A study of the compound eye of the dragonfly brought him to the idea that the resolution of the in 1758 invented achromatic refracting telescope would be enhanced when the instrument was made suitable for two eyes. In 1770 he designed his first binocular achromatic telescope, which he ordered from the well-known optical firm Dollond in London (preserved in the Utrecht University Museum). Although these Grand Binocles were admired by several visiting scholars, the design eventually appeared useless for astronomy. As a failed instrument, Hemsterhuis’ Grand Binocle was forgotten and even skipped from his biography. A second attempt to design such a twin telescope – also composed of two Dollond instruments – was undertaken in the 1860s by William Rutter Dawes. Such a binocular Dollond telescope now survives in the Degenaar Collection in Oud Zuilen (The Netherlands).
Periode27 jul. 2019
Gehouden opScientific Instrument Society, Verenigd Koninkrijk
Mate van erkenningInternationaal