<p>Some of <a href='/search?keyword=Charles%20Mason'>Charles Mason</a>'s computations and comparisons of 1778 for improving his lunar tables, as well as related materials including some comments on <a href='/search?keyword=Tobias%20Mayer'>Tobias Mayer</a>'s original tables. Similar earlier calculations are in volume [<a href='/view/MS-RGO-00004-00085/1'>RGO 4/85</a>]. Mason had originally been involved in the efforts to judge the accuracy of the tables submitted to the Board by Mayer in 1757, which resulted in the solar and lunar tables employed in computing <a href='/search?keyword=Nevil%20Maskelyne'>Nevil Maskelyne</a>'s annual Nautical Almanac. He had already been extensively involved with the Board of Longitude and the <a href='/search?keyword=Greenwich%20Observatory'>Greenwich Observatory</a> in other ways as well when, in his retirement years, he was offered hundreds of pounds to improve the tables.</p> <p>At the Board meeting of 28 November 1772 [<a href='/view/MS-RGO-00014-00005/235'>RGO 14/5:231</a>], Maskelyne presented the other astronomer's suggestions 'for improving Mayer's Tables by lessening the Errors in the method of calculation which he had perfected under the encouragement of the Board ; and at the same time reported that he has reduced the Errors of those Tables to about one half'. Mason was called in and reported that he had been working on it for almost two years. He was rewarded with 250 Guineas, and the Board ordered 'That the said Work be printed under the direction of the Astronomer Royal and Copies delivered to each of the Computers of the Nautical Almanacs'. Six years later, Mason also tried unsuccessfully to claim a reward of 5000 pounds for his efforts, at the Board meeting of 7 March 1778 [<a href='/view/MS-RGO-00014-00005/331'>RGO 14/5:327</a>].</p> <p>Mason issued his initial improved results in 1772 and then improved tables in 1777 and 1781, which were passed on to the 'computers' to be employed in the almanacs and ultimately published in 1787. At the Board meeting of 14 November 1786 [<a href='/view/MS-RGO-00014-00006/1'>RGO 14/6:97</a>], the Commissioners 'Resolved that Mr Mason's last improved Tables of the Moon, and the Folio General Tables of the Moon's distance from the Sun and Zodiacal Stars be immediately published at the price of two shillings each'. (By the time of publication, the aged astronomer had actually died, after he and most of his family moved to America, but his widow later sent the Board his papers relating to the lunar tables in 1793 in return for a reward [<a href='/view/MS-RGO-00014-00012/99'>RGO 14/12:346</a>].)</p> <p>Mason labeled this bound book 'Lunar Tables in Longitude and Latitude, According to the Newtonian Laws of Gravity. by Charles Mason. 1778.' and 'Part of the computation of Mason's Lunar Tables of 1778, and comparison of the Tables, in Longitude and Latitude, with Observations'. The bulk of the contents are tables, often specified as having been computed using the observations of the late Astronomer Royal <a href='/search?keyword=James%20Bradley'>James Bradley</a> for whom Mason had worked, with occasional helpful commentary about equations and observations and the like. Specifically, the contents include computations of lunar longitude and latitude and as compared to Mayer's tables or to observed values, tables [<a href='' onclick='store.loadPage(9);return false;'>4-33</a>] on the annual equation of the anomaly and ascending node of the Moon, and remarks [<a href='' onclick='store.loadPage(5);return false;'>2r-2v</a>] on the subject given to the Board of Longitude.</p> <p>Alexi Baker<br />History and Philosophy of Science<br />University of Cambridge<br /> </p>
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