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Description: | This eyepiece has a focal length of 2.49mm. It has a mount with a small thread and a milled edge.
William Herschel's eyepieces, made for him by his younger brother Alexander are outstanding because of their magnifying power which was exceptionally high for the time.
In his 'Account of a Comet', read to the Royal Society in April 1781 (the comet in question was later confirmed to be Uranus) he referred to having 'ready at hand the several magnifiers of 227, 932, 1536, 2010, &c'.
At the time a power of 270 was considered excellent, and his audiences disbelief at his claims of magnification was a serious hurdle in getting his discovery recognised.
Negative Number D6619
caption: Composition of F3348 and F3340 - Eyepiece Micrometer
caption: Eyepiece | Publisher: | "http://collections.rmg.co.uk/" | Rights holder: | "Royal Museums Greenwich" | Subjects: | A Catalogue of Instruments made and (or) used by Sir William Herschel as Preserved at Slough & examined ther in 1924 May & June A Peep into Herschel's Workshop Focal length eyepieces Sir William Herschel | Source: | Royal Museums Greenwich | Identifier: | http://collections.rmg.co.uk/collections... | Go to resource |
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Eyepiece
This eyepiece was probably made…
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