The obliquity of the ecliptic.
Abstract
In view of the discrepancy between observed and calculated secular rates of change in the mean apparent obliquity of the ecliptic, a reassessment of observed values of the obliquity of the ecliptic is made. Leastsquares adjusted values of the obliquity are derived for a number of epochs (1000 B.C. to A.D. 2000). A simple numerical expression for the obliquity is given which supersedes the standard expression and amply approximates the expected cyclic behavior for a time span of at least 1 million years.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 March 1979
 Bibcode:
 1979A&A....73..129W
 Keywords:

 Astrometry;
 Ecliptic;
 Secular Variations;
 Solar Orbits;
 Chronology;
 Least Squares Method;
 Long Term Effects;
 Tables (Data);
 Astronomy;
 Ecliptic:Obliquity