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Annotation of researchv10dc/cmd/sky/star.c, revision 1.1

1.1     ! root        1: #include "sky.h"
        !             2: 
        !             3: star()
        !             4: {
        !             5:        double capt0, capt1, capt12, capt13;
        !             6:        double sl, sb, cl;
        !             7:        double zt, zee, tht;
        !             8:        double sa, ca, sd;
        !             9: 
        !            10:        capt0 = epoch/36524.220;
        !            11:        capt1 = (eday - epoch)/36524.220;
        !            12:        capt12 = capt1*capt1;
        !            13:        capt13 = capt12*capt1;
        !            14: 
        !            15:        da = da*radsec*15.*100.;
        !            16:        dd = dd*radsec*100.;
        !            17: 
        !            18: /*
        !            19:  *     remove E-terms of aberration
        !            20:  *     except when finding catalog mean places
        !            21:  *     See Exp. Supp. p. 144 and 48
        !            22:  *
        !            23:  *     I have omitted an unimportant time dependence which depends
        !            24:  *     in essence on the change in the eccentricity
        !            25:  *     and the perihelion position of the earths orbit.
        !            26:  */
        !            27: 
        !            28:        alpha = alpha + .341*radsec*sin(alpha+168.8*radian)
        !            29:          /cos(delta);
        !            30:        delta = delta + .341*radsec*cos(alpha+168.8*radian)
        !            31:          *sin(delta) + .029*radsec*cos(delta);
        !            32: 
        !            33: /*
        !            34:  *     Correct for proper motion.
        !            35:  *
        !            36:  *     This computation is a second order approximation which
        !            37:  *     causes no perciptible error in a millenium.
        !            38:  */
        !            39: 
        !            40:        alpha = alpha + capt1*da
        !            41:         + da*dd*sin(delta)/cos(delta)*capt1*capt1;
        !            42:        delta = delta + capt1*dd
        !            43:         - 0.25*da*da*sin(2.*delta)*capt1*capt1;
        !            44: 
        !            45: /*
        !            46:  *     The effect of radial velocity has been omitted.
        !            47:  *     The only bright stars perceptibly affected are
        !            48:  *     Sirius, alpha Cent, and Altair.
        !            49:  */
        !            50: 
        !            51: /*
        !            52:  *     convert mean places at epoch of startable to current
        !            53:  *     epoch (i.e. compute relevant precession)
        !            54:  *     Coefficients are from Exp. Supp. p. 30.
        !            55:  */
        !            56: 
        !            57:        zt = (2304.250 + 1.396*capt0)*capt1 + 0.302*capt12
        !            58:         + 0.018*capt13;
        !            59:        zee = zt + 0.791*capt12;
        !            60:        tht = (2004.682 - 0.853*capt0)*capt1 - 0.426*capt12
        !            61:         - 0.042*capt13;
        !            62: 
        !            63:        zt = zt*radsec;
        !            64:        zee = zee*radsec;
        !            65:        tht = tht*radsec;
        !            66: 
        !            67:        sa = cos(delta)*sin(alpha+zt);
        !            68:        ca = cos(tht)*cos(delta)*cos(alpha+zt) - sin(tht)*sin(delta);
        !            69:        sd = cos(tht)*sin(delta) + sin(tht)*cos(delta)*cos(alpha+zt);
        !            70: 
        !            71:        alpha = atan2(sa,ca) + zee;
        !            72:        delta = atan2(sd, sqrt(sa*sa+ca*ca));
        !            73: 
        !            74: /*
        !            75:  *     convert to mean ecliptic system of date
        !            76:  */
        !            77: 
        !            78:        cl = cos(delta)*cos(alpha);
        !            79:        sl = cos(delta)*sin(alpha)*cos(obliq) + sin(delta)*sin(obliq);
        !            80:        sb = -cos(delta)*sin(alpha)*sin(obliq) + sin(delta)*cos(obliq);
        !            81:        lambda = atan2(sl,cl);
        !            82:        beta = atan2(sb,sqrt(cl*cl+sl*sl));
        !            83:        if(px > 1.0) px = 0.;
        !            84:        if(px != 0.) rad = 1./(radsec*px);
        !            85:        if(px <= 0.) rad = 1.e9;
        !            86:        semi = 0.;
        !            87:        ldot = 0.;
        !            88:        bdot = 0.;
        !            89:        rdot = 0.;
        !            90: 
        !            91:        helio();
        !            92:        geo();
        !            93: }

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