National Maritime Museum Manuscripts : Lunar observations taken on board HM brig Trent by John Franklin

National Maritime Museum Manuscripts

<p>A collection of printed sheets that are designed to assist in the taking of lunars; with spaces left blank for the readings taken whilst at sea they have step by step instructions for the mathematical work that will reduce celestial observations to a longitude measurement. Volumes like this embody an attempt to overcome the complex mathematics involved in finding longitude at sea and in particular this volume contains the reductions to remove the effects of refraction and parallax that accompanies the lunar distance method for finding your longitude. Entitled [<a href='' onclick='store.loadPage(5);return false;'>1</a>] <i>‘Forms for the ready calculation of the longitude by the observed distances of the moon, for the sin or a star, with the tables published by <a href='/search?keyword=Joseph%20de%20Mendoza%20Rios'>Joseph de Mendoza Rios</a>, Esq. FRS’</i> the volume comes with two examples of how the sheets, entitled ‘Calculation of the true distance and of the time at Greenwich' [<a href='' onclick='store.loadPage(6);return false;'>2</a>] and ‘Calculations of the time at the ship and conclusion of the longitude’ [<a href='' onclick='store.loadPage(7);return false;'>3</a>], are to be utilised when entering observations for reduction.</p> <p> <a href='/search?keyword=John%20Franklin'>John Franklin</a> has filled in the blank forms [<a href='' onclick='store.loadPage(12);return false;'>8-17</a>] to find his longitude for May 13th and 14th 1818, next there are several calculations [<a href='' onclick='store.loadPage(22);return false;'>18-35</a>] for the 10th, 11th and 12th of June and then on the 23rd of August [<a href='' onclick='store.loadPage(40);return false;'>36-39</a>] and then again on the 27th of August [<a href='' onclick='store.loadPage(44);return false;'>40-41</a>] at the Observatory in <a href='/search?keyword=Spitsbergen'>Spitsbergen</a> after an unsuccessful venture into the ice north of Spitsbergen. Thereafter there are no further entries. The voyage that Franklin was undertaking when he used this volume was an attempt to go north from Spitsbergen in command of <a href='/search?keyword=HMS%20Trent'> <i>HMS Trent</i> </a>. Fanklin was accompanying Captain <a href='/search?keyword=David%20Buchan'>David Buchan</a> on <a href='/search?keyword=HMS%20Dorothea'> <i>HMS Dorothea</i> </a> in an attempt to find passage to the Bering Strait after Whalers reported open waters extending significantly further north than in previous years. The voyage was rather unsuccessful however as the reported open waters of the previous summer had remained ice in 1818 and the ships were forced to retreat back to open water after being dragged approximately sixty miles by rope through the ice. Once back in open water <a href='/search?keyword=HMS%20Dorothea'> <i>HMS Dorothea</i> </a> was damaged during a storm and Captain Buchan, against Franklin’s desires, decided to return both ships back to England.</p> <p>Sophie Waring<br />History and Philosophy of Science<br />University of Cambridge<br /> </p>

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