Newcomb's Tables of The Sun - Discontinuance

Discontinuance

By 1970 the astronomical community recognized the need for improved ephemerides, which are used to prepare national almanacs. The changes required were

• a new fundamental catalog of stars to replace FK4
• the use of improved values of astronomical constants that had been discovered
• a better definition and practical realization of ephemeris time which would take advantage of atomic time
• a new epoch to replace 1950.0

It was decided to introduce as many changes as possible at one time in a consistent system, and the new system would go into effect for the 1984 edition of the ephemerides. "The majority of the resolutions were prepared and adopted by the General Assembly of the IAU at the 1976 and 1979 meetings."

The new fundamental ephemeris was prepared by the Jet Propulsion Laboratory and named DE200/LE200. It uses numerical integration.