source: Sophya/trunk/SophyaExt/XephemAstroLib/atlas.c@ 3891

/* look up which star atlas an ra/dec is in.
 * Urano and Mill contributed by Atsuo Ohki <ohki@gssm.otsuka.tsukuba.ac.jp>
 * U2K by Robert Lane <roblane@alum.mit.edu>
 *
 * N.B. skylist.c assumes a certain max length for any returned string.
 */
 
#include <stdio.h>
#include <string.h>

#include "astro.h"

/* for Millennium Star Atlas */
static int msa_charts[] = {
    /* 90*/  2, /* 84*/  4, /* 78*/  8, /* 72*/ 10, /* 66*/ 12,
    /* 60*/ 14, /* 54*/ 16, /* 48*/ 20, /* 42*/ 20, /* 36*/ 22,
    /* 30*/ 22, /* 24*/ 24, /* 18*/ 24, /* 12*/ 24, /*  6*/ 24,
    /*  0*/ 24,
    /* -6*/ 24, /*-12*/ 24, /*-18*/ 24, /*-24*/ 24, /*-30*/ 22,
    /*-36*/ 22, /*-42*/ 20, /*-48*/ 20, /*-54*/ 16, /*-60*/ 14,
    /*-66*/ 12, /*-72*/ 10, /*-78*/  8, /*-84*/  4, /*-90*/  2
};

/*
 * find the chart number of Millennium Star Atlas and return pointer to static
 * string describing location.
 * 0 <= ra < 24;  -90 <= dec <= 90
 */
char *
msa_atlas(double ra, double dec)
{
        static char buf[512];
        int zone, band;
        int i, p;

        ra = radhr(ra);
        dec = raddeg(dec);
        buf[0] = 0;
        if (ra < 0.0 || 24.0 <= ra || dec < -90.0 || 90.0 < dec)
            return (buf);
        zone = (int)(ra/8.0);
        band = -((int)(dec+((dec>=0)?3:-3))/6 - 15);
        for (p=0, i=0; i <= band; i++)
            p += msa_charts[i];
        i = (int)((ra - 8.0*zone) / (8.0/msa_charts[band]));
        sprintf(buf, "V%d - P%3d", zone+1, p-i+zone*516);
        return (buf);
}

/* for original Uranometria */
static struct {
    double l;
    int n;
} um_zones[] = {
    /* 84 - 90 */ { 84.5,  2},
    /* 72 - 85 */ { 72.5, 12},
    /* 60 - 73 */ { 61.0, 20},
    /* 49 - 62 */ { 50.0, 24},
    /* 38 - 51 */ { 39.0, 30},
    /* 27 - 40 */ { 28.0, 36},
    /* 16 - 29 */ { 17.0, 45},
    /*  5 - 18 */ {  5.5, 45},
    /*  0 -  6 */ {  0.0, 45},
                  {  0.0,  0}
};

/*
 * find the chart number of Uranometria first edition and return pointer to
 * static string describing location.
 * 0 <= ra < 24;  -90 <= dec <= 90
 */
char *
um_atlas(double ra, double dec)
{
        static char buf[512];
        int band, south;
        int p;
        double w;

        ra = radhr(ra);
        dec = raddeg(dec);
        buf[0] = 0;
        if (ra < 0.0 || 24.0 <= ra || dec < -90.0 || 90.0 < dec)
            return (buf);
        p = 0;
        if (dec < 0.0) {
            dec = -dec;
            south = 1;
        } else
            south = 0;
        p = 1;
        for (band=0; um_zones[band].n; band++) {
            if (um_zones[band].l <= dec)
                break; 
            p += um_zones[band].n;
        }
        if (!um_zones[band].n)
            return (buf);
        w = 24.0 / um_zones[band].n;
        if (band) {
            ra += w/2.0;
            if (ra >= 24.0)
                ra -= 24.0;
        }
        if (south && um_zones[band+1].n)
            p = 475 - p - um_zones[band].n;
        if (south && band == 0) {
            /* south pole part is mis-ordered! */
            ra = 24.0 - ra;
        }
        sprintf(buf, "V%d - P%3d", south+1, p+(int)(ra/w));
        return (buf);
}

/* for Uranometria 2000.0 */
static struct {
    double lowDec;      /* lower dec cutoff */
    int numZones;       /* number of panels (aka zones) */

} u2k_zones[] = { /* array of book layout info */
    /* 84 - 90 */ { 84.5,  1}, /* lower dec cutoff, # of panels in band */
    /* 73 - 85 */ { 73.5,  6},
    /* 62 - 74 */ { 62.0, 10},
    /* 51 - 63 */ { 51.0, 12},
    /* 40 - 52 */ { 40.0, 15},
    /* 29 - 41 */ { 29.0, 18},
    /* 17 - 30 */ { 17.0, 18},
    /*  5 - 18 */ {  5.5, 20},
    /*  0 -  6 */ {  0.0, 20},
                  {  0.0,  0} /*numZones value in this line is a stopper.*/
};

/* find the chart number of Uranometria 2000.0 and return pointer to static
 * string describing location.
 * 0 <= ra < 24;  -90 <= dec <= 90
 */
char *
u2k_atlas(double ra, double dec)
{
        static char buf[512];
        static char err[] = "???";
        int band;               /* index to array */
        int south;              /* flag for volume 2*/
        int panel;              /* panel number */

        ra = radhr(ra);
        dec = raddeg(dec);
        buf[0] = 0;
        if (ra < 0.0 || 24.0 <= ra || dec < -90.0 || 90.0 < dec) {
            strcpy (buf, err);
            return (buf); /* range checking */
        }

        if (dec < 0.0) {
            dec = -dec;
            south = 1; /* South is mirror of North */
        } else
            south = 0;

        panel = 1;
        band = 0;

        /* scan u2k_zones for the correct band: */
        while (u2k_zones[band].numZones != 0 && dec <= u2k_zones[band].lowDec ){
            panel += u2k_zones[band].numZones; /*accumulate total panels */
            band++ ;
        }

        if (!u2k_zones[band].numZones) { /* hit end of array with no match. */
            strcpy (buf, err);
            return (buf);
        }

        ra -= 12.0 / u2k_zones[band].numZones; /*offset by half-width of panel*/
        if (ra >= 24.0)                 /* reality check. shouldn't happen. */
            ra -= 24.0;

        if (ra < 0.0)                   /* offset could give negative ra */
            ra += 24.0;

        if (south && u2k_zones[band+1].numZones)
            panel = 222 - panel - u2k_zones[band].numZones;

        /* resultant panel number is accumulated panels in prior bands plus
         * ra's fraction of panels in dec's band. panel # goes up as ra goes
         * down.
         */
        sprintf(buf, "V%d - P%3d", south+1,
        panel+(int)(u2k_zones[band].numZones*(24.0 - ra)/24.0));

        return (buf);
}


/* For RCS Only -- Do Not Edit */
static char *rcsid[2] = {(char *)rcsid, "@(#) $RCSfile: atlas.c,v $ $Date: 2009-07-16 10:34:36 $ $Revision: 1.6 $ $Name: not supported by cvs2svn $"};