Unpublished letter, 'On a new method of computing the perturbations of planets where eccentricities and inclinations are not small' from Professor [Peter Andreas] Hansen to G B [George Biddell] Airy Copy of a letter in which Hansen provides a mathematical method for computing the perturbations of planets of large eccentricities and inclinations, calculating the perturbations of the comet of Encke produced by Saturn to illustrate his method. Subject: Astronomy Received 28 December 1842. Communicated by Airy. Original letter written by Hansen in Gotha [Germany]. A translation of this letter was published by Airy in The Monthly Notices of the Royal Astronomical Society: Airy, G.B. 'Translation of a Letter from Professor Hansen to G. B. Airy, Esq. the Astronomer Royal, on a New Method of Computing the Perturbations of Planets, whose Eccentricities and Inclinations are not small.' The Monthly Notices of the Royal Astronomical Society, volume 5, number 27 (1843), pp. 227-229. 14 December 1842