Newcomb's Tables of The Sun

Newcomb's Tables Of The Sun

Newcomb's Tables of the Sun is the short title and running head of a work by the American astronomer and mathematician Simon Newcomb entitled "Tables of the Motion of the Earth on its Axis and Around the Sun" on pages 1–169 of "Tables of the Four Inner Planets" (1895), volume VI of the serial publication Astronomical Papers prepared for the use of the American Ephemeris and Nautical Almanac. The work contains Newcomb's mathematical development of the position of the Earth in the Solar System, which is constructed from classical celestial mechanics as well as centuries of astronomical measurements. The bulk of the work, however, is a collection of tabulated precomputed values that provide the position of the sun at any point in time.

Newcomb's Tables were the basis for practically all ephemerides of the Sun published from 1900 through 1983, including the annual almanacs of the U.S. Naval Observatory and the Royal Greenwich Observatory. The tables are seldom used now; since the Astronomical Almanac for 1984 they have been superseded by more accurate numerically-integrated ephemerides developed at Jet Propulsion Laboratory, based on much more accurate observations than were available to Newcomb. Also, the tables did not account for the effects of general relativity which was unknown at the time. Nevertheless, his tabulated values remain accurate to within a few seconds of arc to this day.

Newcomb's work was no small accomplishment, especially considering that it predated the advent of digital computers by more than a half century. Emphasis is often placed on the tables themselves, rather than the underlying theory. The latter may turn out to be the more enduring work because the formulas he developed are still used in astronomical software and other computer algorithms.

Newcomb developed similar formulas and tables for the other planets; those of the inner planets have proved to be the most accurate.