Correspondence with Donald Sadler, including copies of official correspondence between H.M. Nautical Almanac Office and the U.S. Navy N.A.O. The subjects include the use of 'Nautical Almanac' material in the B.A.A. Handbook, with some mention of the copyright position and reproduction fee; the recomputation of Crommelin's Perturbation Tables, mentioning the use of (human) computers in the N.A.O. and British Astronomical Association in September 1947; the use of 'National Machines' in this recomputation and the accuracy and use of Crommelin's Tables; the orbit of Comet Pons-Winnecke during 1939-1945 and a comparison of the Cowell and Crommelin methods; Gerald Merton and his interest in the recomputation of these tables; the change of working method from logaritH.M.S. to machines; the work for the Connaissance des Temps; 'The Night Sky' broadcasts; an ephemeris for Vesta completed up to 31 January 1947; work to be done by Porter for W.H. Steavenson on Ariel (Uranus I); constellation name abbreviations used in the 'Nautical Almanac' and the B.A.A. Handbook; and the installation at the N.A.O. of the I.C.T. 1909 electronic computer. There is also miscellaneous correspondence with the U.S. Navy N.A.O. regarding the 'Nautical Almanac', the 'Air Almanac' and the 'Astronomical Ephemeris', including reference to changes to be made in the 1966 edition to the tabulation of information on Saturn's satellites and the subsequent revision of the 1970 'Astronomical Ephemeris'.