Ernest William Brown - Legacy

Legacy

Brown's Tables were adopted by nearly all of the national ephemerides in 1923 for their calculations of the Moon's position, and continued to be used, eventually with some modification, until 1983. With the advent of digital computers, Brown's original trigonometrical expressions, given in the introduction to his 1919 tables (and from which the tables had been compiled), began to be used for direct computation instead of the tables themselves. This also gained some improvement in precision, since the tables themselves had embodied some minor approximations, in a trade-off between accuracy and the amount of labor need for computations using the tables in those days of manual calculation. By mid-century, the difference between Universal and Ephemeris Time had been recognised and evaluated, and the troublesome empirical terms were also removed. Further adjustments to Brown's theory were then also made in a later stage, arising from improved observational values of the fundamental astronomical constants used in the theory, and from re-working Brown's original analytical expansions to gain more precise versions of the coefficients used in the theory.

It was only as recently as in the ephemerides for 1984 that Brown's work was superseded: it was replaced by results gained from more modern observational data (including data from lunar laser ranging) and by altogether new computational methods for calculating the Moon's ephemeris.