pub fn atciqz(rc: f64, dc: f64, astrom: &mut IauAstrom) -> (f64, f64)Expand description
Quick astrometric ICRS −> CIRS
Quick ICRS to CIRS transformation, given precomputed star- independent astrometry parameters, and assuming zero parallax and proper motion.
Use of this function is appropriate when efficiency is important and where many star positions are to be transformed for one date. The star-independent parameters can be obtained by calling one of the functions iauApci[13], iauApcg[13], iauApco[13] or iauApcs[13].
The corresponding function for the case of non-zero parallax and proper motion is iauAtciq.
This function is part of the International Astronomical Union’s SOFA (Standards of Fundamental Astronomy) software collection.
Status: support function.
Given:
rc,dc double ICRS astrometric RA,Dec (radians)
astrom iauASTROM* star-independent astrometry parameters:
pmt double PM time interval (SSB, Julian years)
eb double[3] SSB to observer (vector, au)
eh double[3] Sun to observer (unit vector)
em double distance from Sun to observer (au)
v double[3] barycentric observer velocity (vector, c)
bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor
bpn double[3][3] bias-precession-nutation matrix
along double longitude + s' (radians)
xpl double polar motion xp wrt local meridian (radians)
ypl double polar motion yp wrt local meridian (radians)
sphi double sine of geodetic latitude
cphi double cosine of geodetic latitude
diurab double magnitude of diurnal aberration vector
eral double "local" Earth rotation angle (radians)
refa double refraction constant A (radians)
refb double refraction constant B (radians)Returned:
ri,di double CIRS RA,Dec (radians)Note:
All the vectors are with respect to BCRS axes.
References:
Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to the Astronomical Almanac, 3rd ed., University Science Books (2013).
Klioner, Sergei A., “A practical relativistic model for micro- arcsecond astrometry in space”, Astr. J. 125, 1580-1597 (2003).
Called:
iauS2c spherical coordinates to unit vector
iauLdsun light deflection due to Sun
iauAb stellar aberration
iauRxp product of r-matrix and p-vector
iauC2s p-vector to spherical
iauAnp normalize angle into range +/- pi