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- atciqz

# atciqz

erfa.atciqz(rc, dc, astrom)

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

  Parameters:
    rc double array
    dc double array
    astrom eraASTROM array
  Returns:
    ri double array
    di double 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.