Thorp Diffraction Gratings

Forums History Thorp Diffraction Gratings

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    David Strange
    The NLO have kindly been donated some historic diffraction gratings made in 1900 by Thomas Thorp. These originally belonged to James Lockyer (Norman Lockyer’s son).
    This photo of one of them was signed “With T Thorp’s compliments May 16th 1900” and belonged originally to William Abney who presumably then gave it to Lockyer.
    This is also written on the grating: “Thorp’s transparent Replica of Rowland’s Metal Diffraction grating  14,555 lines to the inch.”

    From Wikipedia:
    Thomas Thorp: (1850­1914)  A “scientific and mechanical genius”. Credited with designing and building the first coin in the slot gas meter.
    Went on to developed considerable skills in the manufacture of optical glass and both reflector and refractor telescopes. He also created celluloid diffraction grating replicas, polarising solar eyepieces and prominence spectroscopes that were widely used, as well as objective prisms. His high resolution diffracting grating replicas were significant advances of the ideas developed by Henry Rowland. Thorp’s “brilliant idea”, announced in 1898 and improved thereafter through experimentation and the development of new materials, was to take “a cast of the ruled surface in a transparent medium [comprising] a thin solution of celluloid in amyl acetate.

    … the study of spectroscopic astrophysics possible to so many lovers of the science. In addition to putting these on the market at a moderate price, he was most lavish in his generous distribution of them to professional and amateur workers throughout the world.

    Biography of William Abney: Pioneering photographer who developed the dry photographic plate and photographed the infra-red solar spectrum.

    David Strange
    Norman Lockyer Observatory
    Jeremy Shears

    Very interesting, David. What do you intend to do with the gratings?

    Thomas Thorp was a BAA member, joining in 1892, and a leading light in the North-Western Branch, in Manchester, where he served as Vice President. A brief JBAA obituary appears in JBAA, vol 24 (10), page 503, October 1914:

    We regret to record the death of Mr. T. Thorp which occurred on 13th June last at his home, Whitefield, near Manchester. He was educated at the Manchester Grammar School, and resided in Manchester all his life. He devoted much of his time and attention to the improvement of astronomical instruments. His replica gratings, invented several years ago, brought him into prominence as a pioneer in this department of instrumental mechanism. Many of our members have reason to be grateful to Mr. Thorp for supplying them with prism gratings, applicable to binoculars, which have proved so serviceable in the observation of total solar eclipses. Ho joined this Association in 1892, became a member of the Manchester Literary and Philosophical Society in 1896, and was elected a Fellow of the Royal Astronomical Society in 1902.

    All the best,


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