#include "sofa.h" void iauAtoiq(const char *type, double ob1, double ob2, iauASTROM *astrom, double *ri, double *di) /* ** - - - - - - - - - ** i a u A t o i q ** - - - - - - - - - ** ** Quick observed place to CIRS, given the star-independent astrometry ** parameters. ** ** Use of this function is appropriate when efficiency is important and ** where many star positions are all to be transformed for one date. ** The star-independent astrometry parameters can be obtained by ** calling iauApio[13] or iauApco[13]. ** ** Status: support function. ** ** Given: ** type char[] type of coordinates: "R", "H" or "A" (Note 1) ** ob1 double observed Az, HA or RA (radians; Az is N=0,E=90) ** ob2 double observed ZD or 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 double* CIRS right ascension (CIO-based, radians) ** di double* CIRS declination (radians) ** ** Notes: ** ** 1) "Observed" Az,El means the position that would be seen by a ** perfect geodetically aligned theodolite. This is related to ** the observed HA,Dec via the standard rotation, using the geodetic ** latitude (corrected for polar motion), while the observed HA and ** RA are related simply through the Earth rotation angle and the ** site longitude. "Observed" RA,Dec or HA,Dec thus means the ** position that would be seen by a perfect equatorial with its ** polar axis aligned to the Earth's axis of rotation. By removing ** from the observed place the effects of atmospheric refraction and ** diurnal aberration, the CIRS RA,Dec is obtained. ** ** 2) Only the first character of the type argument is significant. ** "R" or "r" indicates that ob1 and ob2 are the observed right ** ascension and declination; "H" or "h" indicates that they are ** hour angle (west +ve) and declination; anything else ("A" or ** "a" is recommended) indicates that ob1 and ob2 are azimuth (north ** zero, east 90 deg) and zenith distance. (Zenith distance is used ** rather than altitude in order to reflect the fact that no ** allowance is made for depression of the horizon.) ** ** 3) The accuracy of the result is limited by the corrections for ** refraction, which use a simple A*tan(z) + B*tan^3(z) model. ** Providing the meteorological parameters are known accurately and ** there are no gross local effects, the predicted observed ** coordinates should be within 0.05 arcsec (optical) or 1 arcsec ** (radio) for a zenith distance of less than 70 degrees, better ** than 30 arcsec (optical or radio) at 85 degrees and better than ** 20 arcmin (optical) or 30 arcmin (radio) at the horizon. ** ** Without refraction, the complementary functions iauAtioq and ** iauAtoiq are self-consistent to better than 1 microarcsecond all ** over the celestial sphere. With refraction included, consistency ** falls off at high zenith distances, but is still better than ** 0.05 arcsec at 85 degrees. ** ** 4) It is advisable to take great care with units, as even unlikely ** values of the input parameters are accepted and processed in ** accordance with the models used. ** ** Called: ** iauS2c spherical coordinates to unit vector ** iauC2s p-vector to spherical ** iauAnp normalize angle into range 0 to 2pi ** ** This revision: 2013 October 9 ** ** SOFA release 2016-05-03 ** ** Copyright (C) 2016 IAU SOFA Board. See notes at end. */ { 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. */ iauS2c ( -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. */ iauC2s(v, &hma, di); /* Right ascension. */ *ri = iauAnp(astrom->eral + hma); /* Finished. */ /*---------------------------------------------------------------------- ** ** Copyright (C) 2016 ** Standards Of Fundamental Astronomy Board ** of the International Astronomical Union. ** ** ===================== ** SOFA Software License ** ===================== ** ** NOTICE TO USER: ** ** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND ** CONDITIONS WHICH APPLY TO ITS USE. ** ** 1. The Software is owned by the IAU SOFA Board ("SOFA"). ** ** 2. Permission is granted to anyone to use the SOFA software for any ** purpose, including commercial applications, free of charge and ** without payment of royalties, subject to the conditions and ** restrictions listed below. ** ** 3. You (the user) may copy and distribute SOFA source code to others, ** and use and adapt its code and algorithms in your own software, ** on a world-wide, royalty-free basis. 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