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Annotation of researchv10no/cmd/sky/helio.c, revision 1.1

1.1     ! root        1: #include "sky.h"
        !             2: 
        !             3: helio()
        !             4: {
        !             5: /*
        !             6:  *     uses lambda, beta, rad, motion
        !             7:  *     uses xms, yms, zms, xdot, ydot, zdot
        !             8:  *     uses mag, semi, psi, tobliq
        !             9:  *     sets alpha, delta
        !            10:  *     sets geolam, geobet, georad
        !            11:  */
        !            12: 
        !            13: /*
        !            14:  *     helio converts from ecliptic heliocentric coordinates
        !            15:  *     referred to the mean equinox of date
        !            16:  *     to equatorial geocentric coordinates referred to
        !            17:  *     the true equator and equinox
        !            18:  */
        !            19: 
        !            20:        double xmp, ymp, zmp;
        !            21:        double radtemp;
        !            22: 
        !            23: /*
        !            24:  *     compute geocentric distance of object and
        !            25:  *     compute light-time correction (i.i. planetary aberration)
        !            26:  */
        !            27: 
        !            28:        xmp = rad*cos(beta)*cos(lambda);
        !            29:        ymp = rad*cos(beta)*sin(lambda);
        !            30:        zmp = rad*sin(beta);
        !            31:        georad = sqrt((xmp+xms)*(xmp+xms) +
        !            32:                (ymp+yms)*(ymp+yms) +
        !            33:                (zmp+zms)*(zmp+zms));
        !            34:        geolam = lambda - .0057756e0*georad*ldot;
        !            35:        geobet = beta - .0057756*georad*bdot;
        !            36:        radtemp = georad;
        !            37:        georad = rad - .0057756*georad*rdot;
        !            38: 
        !            39:        xmp = georad*cos(geobet)*cos(geolam);
        !            40:        ymp = georad*cos(geobet)*sin(geolam);
        !            41:        zmp = georad*sin(geobet);
        !            42: 
        !            43: /*
        !            44:  *     compute annual parallax from the position of the sun
        !            45:  */
        !            46: 
        !            47:        xmp += xms;
        !            48:        ymp += yms;
        !            49:        zmp += zms;
        !            50:        georad = sqrt(xmp*xmp + ymp*ymp + zmp*zmp);
        !            51: 
        !            52: /*
        !            53:  *     compute annual (i.e. stellar) aberration
        !            54:  *     from the orbital velocity of the earth
        !            55:  *     (by an incorrect method)
        !            56:  */
        !            57: 
        !            58:        xmp -= xdot*georad;
        !            59:        ymp -= ydot*georad;
        !            60:        zmp -= zdot*georad;
        !            61: 
        !            62: /*
        !            63:  *     perform the nutation and so convert from the mean
        !            64:  *     equator and equinox to the true
        !            65:  */
        !            66: 
        !            67:        geolam = atan2(ymp, xmp);
        !            68:        geobet = atan2(zmp, sqrt(xmp*xmp+ymp*ymp));
        !            69:        geolam += psi;
        !            70: 
        !            71: /*
        !            72:  *     change to equatorial coordinates
        !            73:  */
        !            74: 
        !            75:        xmp = georad*cos(geolam)*cos(geobet);
        !            76:        ymp = georad*(sin(geolam)*cos(geobet)*cos(tobliq) - sin(tobliq)*sin(geobet));
        !            77:        zmp = georad*(sin(geolam)*cos(geobet)*sin(tobliq) + cos(tobliq)*sin(geobet));
        !            78: 
        !            79:        alpha = atan2(ymp, xmp);
        !            80:        delta = atan2(zmp, sqrt(xmp*xmp+ymp*ymp));
        !            81: 
        !            82:        hp = 8.794e0*radsec/georad;
        !            83:        semi /= georad;
        !            84:        georad = radtemp;
        !            85:        if(rad > 0. && rad < 2.e5)
        !            86:                mag += 2.17*log(rad*georad);
        !            87: }

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