Macros | Functions
epsilon.c File Reference

Calculate the obliquity of the ecliptic. More...

#include <stdio.h>
#include "aephem.h"


 Use William's obliquity calculations (c.f. AE_PRECESS_USE_WILLIAMS).
 Use Simon's et al obliquity calculations (c.f. AE_PRECESS_USE_SIMON).


double ae_epsilon (double jd_tt)
 Calculate the obliquity of the ecliptic. More...

Detailed Description

Calculate the obliquity of the ecliptic.

Function Documentation

double ae_epsilon ( double  jd_tt)

Calculate the obliquity of the ecliptic.

J. L. Simon, P. Bretagnon, J. Chapront, M. Chapront-Touze', G. Francou, and J. Laskar, "Numerical Expressions for precession formulae and mean elements for the Moon and the planets," Astronomy and Astrophysics 282, 663-683 (1994).

IAU Coefficients are from: J. H. Lieske, T. Lederle, W. Fricke, and B. Morando, "Expressions for the Precession Quantities Based upon the IAU (1976) System of Astronomical Constants," Astronomy and Astrophysics 58, 1-16 (1977).

Before or after 200 years from J2000, the formula used is from: J. Laskar, "Secular terms of classical planetary theories using the results of general theory," Astronomy and Astrophysics 157, 59070 (1986).

See precess.c and page B18 of the Astronomical Almanac.

jd_ttThe Julian date in TT.
The obliquity, in seconds of arc.

Referenced by ae_geocentric_moon_from_orbit(), ae_gmoon(), ae_kepler(), ae_precess(), ae_rect_to_polar_with_jd(), ae_topocentric(), aes_last(), and aes_nutate().