Astronomical Applications Department, U.S. Naval Observatory novas c 2 doc (Page 32)

void cel_pole (double del_dpsi, double del_deps)

PURPOSE:
This function allows for the specification of celestial pole
offsets for high-precision applications. These are added
to the nutation parameters delta psi and delta epsilon.

INPUT
ARGUMENTS:
del_dpsi (double)
Value of offset in delta psi (dpsi) in arcseconds.
del_deps (double)
Value of offset in delta epsilon (deps) in arcseconds.

OUTPUT
ARGUMENTS:
None.

RETURNED
VALUE:
None.

Discussion:

This function allows for the specification of celestial pole offsets for high precision

(better than 0.1 arcsecond) applications. The offsets are subsequently applied as
corrections to the nutation in longitude and nutation in obliquity within earthtilt. Thus,
earthtilt's output arguments

will be affected. Since other

NOVAS subroutines require earthtilt to obtain data related to the Earth's orientation in
space, the celestial pole offsets specified here are propagated through the data that the
various NOVAS-C functions provide.

Daily values of the celestial pole offsets are published, for example, in IERS Bulletins

A and B. The celestial pole offsets effectively correct for errors or incompleteness in the
standard precession or nutation models, and are needed for conformity with the ICRS
system. If you use cel_pole, make sure it is called before any other functions for a given
date. Values of the pole offsets that you specify by a call to cel_pole will be used by
earthtilt until you explicitly change them.

Astronomical Applications Department, U.S. Naval Observatory - novas c 2 doc (Page 32)