British mathematician, astronomer, and inventor (1792–1871) known for his discoveries related to the moons of Saturn and Uranus and for his pioneering work in early photographic processes, including coining the word ‘photography’ itself. ALS signed “J. F. W. Herschel,” four pages on two adjoining sheets, 7.75 x 9.75, July 24, 1828. Letter to Mr. Henn, discussing a paper written by Henn. In part: “Let me first acknowledge your communication on object glasses and on the planetary ephemerides, if I have not already done so, with the tables and the letters accompanying them. They are printed (not the letters) in the forthcoming volume of the Astron. society's transactions. I have now the proof sheets of the former before me, on which allow me some remarks.” He goes on at length to offer several corrections, with excellent mathematical and scientific content. He continues, “I hope you will now not think me a very severe critic when I tell you that I think very highly of your paper, as a most useful practical work, and which promises to be of the greatest service. A gentleman named Rogers of Lieth has made a considerable improvement (as promised) in the construction of Large telescopes—he corrects a large disc of Crown by a compound lens of crown x flint of much smaller aperture [Herschel draws a demonstrative diagram here]…Your catalogues of stars whose proper motions come out from your obsns so well, are excellent examples. I wish all astronomers would go & do likewise work much dispute little—use their eyes & draw conclusions the best they can, and trust the next sensation with their fame. I shall shortly find a way to send you my 3d Catalogue of new double stars—this completes my first thousand. What a wonderful work Struve's Catalogue is! My nebulae get on slowly but steadily. Within the last few days I have been examining the Satellites of Uranus. About two there remains no doubt—and I am almost sure there are more, but the planet is most unfavorably situated.” In fine condition, with intersecting folds, a few small notations (including his signature underlined at the top of the first page), and repaired paper loss from seal removal.
During this period, Herschel was serving as president of the Royal Astronomical Society, referencing one of the organization’s soon-to-come publications near the beginning of this letter. In earlier years he had extensively studied mathematics and built his own telescope, making him an ideal reviewer for a paper that apparently used complex mathematics in its exploration of objective lenses. Although harsh at times, Herschel’s criticism was well informed by his theoretical and practical experience, and was surely useful to his correspondent. He would go to South Africa in 1834 to catalogue the stars, nebulae, and other objects of the southern skies, using his knowledge to build an impressive 21-foot telescope for this purpose. A wonderful letter rife with important content that applies to Herschel’s endeavors in mathematics, physics, and astronomy. Pre-certified John Reznikoff/PSA/DNA.
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