In an article on “Aerial Navigation,” by Lieutenant Commander Weems (U. S. Naval Institute Proceedings, vol. 55, No. 314, April, 1929), the subject was divided into four sections, the fourth of which, celo-navigation, was defined as that part of aerial navigation in which the position of the observer is found by observations of heavenly bodies, the sun, moon, stars, and planets.
In these notes it is proposed to deal only with celo-navigation and to describe the two instruments officially designed and adopted by the Royal Air Force for this purpose. These instruments have also been adopted by many other European aviators and were used by the Marquis de Pinedo on his flight to America.