Secular Trends in the Mean Longitudes of Planets Derived from Optical Observations
Kolesnik, Yuri B.; Masreliez, C. Johan
Russia, United States
Abstract
About 240,000 worldwide optical observations of the Sun, Mercury, and Venus, accumulated during the entire era of classical astrometry from James Bradley up to the present, are used to analyze the secular longitude variations of the innermost planets. A reduction method relating historical planetary observations to the Hipparcos reference frame is presented. Secular trends in the longitudes of the Sun, Mercury, and Venus with respect to the ephemeris DE405 are estimated for the time span 1750-2000.