Astronomical Applications Department, U.S. Naval Observatory novas c 2 doc Page 31
31
4.16
EARTHTILT
void earthtilt (double tjd,
double *mobl, double *tobl, double *eq, double *dpsi,
double *deps)
PURPOSE:
Computes quantities related to the orientation of the Earth's
rotation axis at Julian date 'tjd'.
INPUT
ARGUMENTS:
tjd (double)
TDB Julian date of the desired time
OUTPUT
ARGUMENTS:
*mobl (double)
Mean obliquity of the ecliptic in degrees at 'tjd'.
*tobl (double)
True obliquity of the ecliptic in degrees at 'tjd'.
*eq (double)
Equation of the equinoxes in seconds of time at 'tjd'.
*dpsi (double)
Nutation in longitude in arcseconds at 'tjd'.
*deps (double)
Nutation in obliquity in arcseconds at 'tjd'.
RETURNED
VALUE:
None.
Discussion:
This function computes various quantities related to the orientation of the Earth's
rotation axis in inertial space at a specific time. The computation involves a call to
function nutation_angles to evaluate the nutation series. The output values of the last
four arguments will correctly reflect the celestial pole offsets if function cel_pole has
previously been called. A call to cel_pole is required for ICRS compatibility.
