void eraAtoiq	(	const char *	type,
		double	ob1,
		double	ob2,
		eraASTROM *	astrom,
		double *	ri,
		double *	di
	)

Definition at line 3 of file atoiq.c.

References eraASTROM::cphi, eraASTROM::diurab, eraAnp(), eraC2s(), eraASTROM::eral, eraS2c(), eraASTROM::refa, eraASTROM::refb, eraASTROM::sphi, eraASTROM::xpl, and eraASTROM::ypl.

Referenced by eraAtoc13(), eraAtoi13(), and t_atoiq().

{
   int c;
   double c1, c2, sphi, cphi, ce, xaeo, yaeo, zaeo, v[3],
          xmhdo, ymhdo, zmhdo, az, sz, zdo, refa, refb, tz, dref,
          zdt, xaet, yaet, zaet, xmhda, ymhda, zmhda,
          f, xhd, yhd, zhd, xpl, ypl, w, hma;

/* Coordinate type. */
   c = (int) type[0];

/* Coordinates. */
   c1 = ob1;
   c2 = ob2;

/* Sin, cos of latitude. */
   sphi = astrom->sphi;
   cphi = astrom->cphi;

/* Standardize coordinate type. */
   if ( c == 'r' || c == 'R' ) {
      c = 'R';
   } else if ( c == 'h' || c == 'H' ) {
      c = 'H';
   } else {
      c = 'A';
   }

/* If Az,ZD, convert to Cartesian (S=0,E=90). */
   if ( c == 'A' ) {
      ce = sin(c2);
      xaeo = - cos(c1) * ce;
      yaeo = sin(c1) * ce;
      zaeo = cos(c2);

   } else {

   /* If RA,Dec, convert to HA,Dec. */
      if ( c == 'R' ) c1 = astrom->eral - c1;

   /* To Cartesian -HA,Dec. */
      eraS2c ( -c1, c2, v );
      xmhdo = v[0];
      ymhdo = v[1];
      zmhdo = v[2];

   /* To Cartesian Az,El (S=0,E=90). */
      xaeo = sphi*xmhdo - cphi*zmhdo;
      yaeo = ymhdo;
      zaeo = cphi*xmhdo + sphi*zmhdo;
   }

/* Azimuth (S=0,E=90). */
   az = ( xaeo != 0.0 || yaeo != 0.0 ) ? atan2(yaeo,xaeo) : 0.0;

/* Sine of observed ZD, and observed ZD. */
   sz = sqrt ( xaeo*xaeo + yaeo*yaeo );
   zdo = atan2 ( sz, zaeo );

/*
** Refraction
** ----------
*/

/* Fast algorithm using two constant model. */
   refa = astrom->refa;
   refb = astrom->refb;
   tz = sz / zaeo;
   dref = ( refa + refb*tz*tz ) * tz;
   zdt = zdo + dref;

/* To Cartesian Az,ZD. */
   ce = sin(zdt);
   xaet = cos(az) * ce;
   yaet = sin(az) * ce;
   zaet = cos(zdt);

/* Cartesian Az,ZD to Cartesian -HA,Dec. */
   xmhda = sphi*xaet + cphi*zaet;
   ymhda = yaet;
   zmhda = - cphi*xaet + sphi*zaet;

/* Diurnal aberration. */
   f = ( 1.0 + astrom->diurab*ymhda );
   xhd = f * xmhda;
   yhd = f * ( ymhda - astrom->diurab );
   zhd = f * zmhda;

/* Polar motion. */
   xpl = astrom->xpl;
   ypl = astrom->ypl;
   w = xpl*xhd - ypl*yhd + zhd;
   v[0] = xhd - xpl*w;
   v[1] = yhd + ypl*w;
   v[2] = w - ( xpl*xpl + ypl*ypl ) * zhd;

/* To spherical -HA,Dec. */
   eraC2s(v, &hma, di);

/* Right ascension. */
   *ri = eraAnp(astrom->eral + hma);

/* Finished. */

}

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