atciqz¶

erfa.atciqz(rc, dc, astrom)[source]¶

Quick ICRS to CIRS transformation, given precomputed star- independent astrometry parameters, and assuming zero parallax and proper motion.

Parameters:

rcdouble array
dcdouble array
astromeraASTROM array

Returns:

ridouble array
didouble array

Notes

Wraps ERFA function eraAtciqz. The ERFA documentation is:

- - - - - - - - - -
 e r a A t c i q z
- - - - - - - - - -

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 eraApci[13], eraApcg[13], eraApco[13] or eraApcs[13].

The corresponding function for the case of non-zero parallax and
proper motion is eraAtciq.

Given:
   rc,dc  double     ICRS astrometric RA,Dec (radians)
   astrom eraASTROM* 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:
   eraS2c       spherical coordinates to unit vector
   eraLdsun     light deflection due to Sun
   eraAb        stellar aberration
   eraRxp       product of r-matrix and p-vector
   eraC2s       p-vector to spherical
   eraAnp       normalize angle into range +/- pi

This revision:   2013 October 9

Copyright (C) 2013-2023, NumFOCUS Foundation.
Derived, with permission, from the SOFA library.  See notes at end of file.

Navigation

atciqz¶