The Role of Occultations in the Improvement of the Lunar Ephemeris

Abstract

Analyses of occultation timings show that periodic correction terms with semi-amplitude as great as 0.″18 arise from corrections required to the empirical constants of the Brown/Eckert theory. Using the atomic time-scale, some of the occultation data have been used to determine a correction of – 30 ± 16″/cy2 to Spencer Jones' value for the secular acceleration of the Moon. In the light of this correction, and previous determinations, attention is drawn to the possible weakness of Spencer Jones' value, which is not reflected in his quoted error of ± 1″/cy2. Further analyses of 50000 occultations observed since 1943 promise to reveal more accurately-determined corrections.