Practical observations on telescopes.

  • William Kitchiner
Date:
1815
Catalogue details

Licence: Public Domain Mark

Credit: Practical observations on telescopes. Source: Wellcome Collection.

    66/116 page 64
    At the sale of Mr, Aubert’s incomparable collection of astronomical instruments, I purchased the celebrated achromatic of forty-six inches focus, with a triple object- glass of three inches and three-quarters aperture, which was originally fitted up by Mr. Ramsden for the Honourable Topham Beauclerc, and Mr. Ramsden’s name is engraven on the eye-end of the telescope : but Mr. Peter Dollond informed me that he made the object-glass, and, smiling at the time he gave me this information, said, “ Yes, that object-glass is one ©f the things u which is to make me immortaland appeared much pleased with the permis¬ sion I gave him to engrave his title to it on the tube of the telescope. To have com¬ posed such a perfect piece of art, is so honourable to the talents of an artist, that, to avoid all appearance of partiality or pre- than when only one is used, the advantage to vision thereby is much less than we might expect. And Dr. Irwin has proved, by a variety of experiments, that it appears only one thirteenth part brighter than when seen with only one eye.
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