The Editor welcomes this opportunity of publishing an account of the valuable and fundamental work done by the Navigation Section of the Aeroplane and Armament Experimental Establishment at Boscombe Down. Some of the results have previously appeared in reports with limited circulation, but no full account has yet been published.

The Navigation Section of Aeroplane & Armament Experimental Establishment (A. & A.E.E.) had, at the outbreak of war in 1939, only recently been established, and was in the charge of Squadron Leader (later Air Commodore) D. J. Waghorn, who was followed by Wing Commander W. S. Jenkins. Both of these officers were keenly interested in methods of astronomical navigation, and in development work. Professor H. H. Plaskett, F.R.S., Savilian Professor of Astronomy at Oxford, was attached to the section, and brought to it an invaluable experience in observational theory and techniques.

The work of the section in the earlier part of the war mirrors exactly the state of knowledge in astronomical methods in navigation at that time. A bubble sextant, the Mk. VIII, had been in use for some time, although knowledge of astronomical methods was limited to comparatively few highly trained members of aircrew. The potentialities of astro-navigation were appreciated, however, and the Mk. IX sextant was being developed.