/************************************************************************
 * Copyright (C) 1996-2003, International Business Machines Corporation *
 * and others. All Rights Reserved.                                     *
 ************************************************************************
 *  2003-nov-07   srl       Port from Java
 */

#include "astro.h"

#if !UCONFIG_NO_FORMATTING

#include "unicode/calendar.h"
#include "math.h"
#include <float.h>

#ifdef U_DEBUG_ASTRO
# include <stdio.h>
# include "uresimp.h" // for debugging

static void debug_astro_loc(const char *f, int32_t l)
{
  fprintf(stderr, "%s:%d: ", f, l);
}

static void debug_astro_msg(const char *pat, ...)
{
  va_list ap;
  va_start(ap, pat);
  vfprintf(stderr, pat, ap);
  fflush(stderr);
}
#include "unicode/datefmt.h"
#include "unicode/ustring.h"
static const char * debug_astro_date(UDate d) {
  static char gStrBuf[1024];
  static DateFormat *df = NULL;
  if(df == NULL) {
    df = DateFormat::createDateTimeInstance(DateFormat::MEDIUM, DateFormat::MEDIUM, Locale::getUS());
    df->adoptTimeZone(TimeZone::getGMT()->clone());
  }
  UnicodeString str;
  df->format(d,str);
  u_austrncpy(gStrBuf,str.getTerminatedBuffer(),sizeof(gStrBuf)-1);
  return gStrBuf;
}

// must use double parens, i.e.:  U_DEBUG_ASTRO_MSG(("four is: %d",4));
#define U_DEBUG_ASTRO_MSG(x) {debug_astro_loc(__FILE__,__LINE__);debug_astro_msg x;}
#else
#define U_DEBUG_ASTRO_MSG(x)
#endif


/**
     * The number of standard hours in one sidereal day.
     * Approximately 24.93.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const double CalendarAstronomer::SIDEREAL_DAY = 23.93446960027;
    
/**
     * The number of sidereal hours in one mean solar day.
     * Approximately 24.07.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const double CalendarAstronomer::SOLAR_DAY =  24.065709816;
    
/**
     * The average number of solar days from one new moon to the next.  This is the time
     * it takes for the moon to return the same ecliptic longitude as the sun.
     * It is longer than the sidereal month because the sun's longitude increases
     * during the year due to the revolution of the earth around the sun.
     * Approximately 29.53.
     *
     * @see #SIDEREAL_MONTH
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const double CalendarAstronomer::SYNODIC_MONTH = 29.530588853;
    
/**
     * The average number of days it takes
     * for the moon to return to the same ecliptic longitude relative to the
     * stellar background.  This is referred to as the sidereal month.
     * It is shorter than the synodic month due to
     * the revolution of the earth around the sun.
     * Approximately 27.32.
     *
     * @see #SYNODIC_MONTH
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const double CalendarAstronomer::SIDEREAL_MONTH = 27.32166;
    
/**
     * The average number number of days between successive vernal equinoxes.
     * Due to the precession of the earth's
     * axis, this is not precisely the same as the sidereal year.
     * Approximately 365.24
     *
     * @see #SIDEREAL_YEAR
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const double CalendarAstronomer::TROPICAL_YEAR = 365.242191;
    
/**
     * The average number of days it takes
     * for the sun to return to the same position against the fixed stellar
     * background.  This is the duration of one orbit of the earth about the sun
     * as it would appear to an outside observer.
     * Due to the precession of the earth's
     * axis, this is not precisely the same as the tropical year.
     * Approximately 365.25.
     *
     * @see #TROPICAL_YEAR
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const double CalendarAstronomer::SIDEREAL_YEAR = 365.25636;

//-------------------------------------------------------------------------
// Time-related constants
//-------------------------------------------------------------------------

    /** 
     * The number of milliseconds in one second. 
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const int32_t  CalendarAstronomer::SECOND_MS = 1000;

/** 
     * The number of milliseconds in one minute. 
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const int32_t  CalendarAstronomer::MINUTE_MS = 60*SECOND_MS;

/** 
     * The number of milliseconds in one hour. 
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const int32_t  CalendarAstronomer::HOUR_MS   = 60*MINUTE_MS;

/** 
     * The number of milliseconds in one day. 
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const  double CalendarAstronomer::DAY_MS    = 24.*HOUR_MS;

/**
     * The start of the julian day numbering scheme used by astronomers, which
     * is 1/1/4713 BC (Julian), 12:00 GMT.  This is given as the number of milliseconds
     * since 1/1/1970 AD (Gregorian), a negative number.
     * Note that julian day numbers and
     * the Julian calendar are <em>not</em> the same thing.  Also note that
     * julian days start at <em>noon</em>, not midnight.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const double CalendarAstronomer::JULIAN_EPOCH_MS = -210866760000000.0;
    
    
/**
 * Milliseconds value for 0.0 January 2000 AD.
 */
const double CalendarAstronomer::EPOCH_2000_MS = 946598400000.0;

//-------------------------------------------------------------------------
// Assorted private data used for conversions
//-------------------------------------------------------------------------

    // My own copies of these so compilers are more likely to optimize them away
const double CalendarAstronomer::PI = 3.14159265358979323846;
const double CalendarAstronomer::PI2 = CalendarAstronomer::PI * 2.0;
const double CalendarAstronomer::RAD_HOUR = 12 / CalendarAstronomer::PI;        // radians -> hours
const double CalendarAstronomer::DEG_RAD  = CalendarAstronomer::PI / 180;        // degrees -> radians
const double CalendarAstronomer::RAD_DEG  = 180 / CalendarAstronomer::PI;        // radians -> degrees
    
//-------------------------------------------------------------------------
// Constructors
//-------------------------------------------------------------------------

/**
 * Construct a new <code>CalendarAstronomer</code> object that is initialized to
 * the current date and time.
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
CalendarAstronomer::CalendarAstronomer():
  fTime(Calendar::getNow()), moonPosition(NULL) {
}
    
/**
 * Construct a new <code>CalendarAstronomer</code> object that is initialized to
 * the specified date and time.
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
CalendarAstronomer::CalendarAstronomer(UDate d): fTime(d),moonPosition(NULL) {
}

/**
 * Construct a new <code>CalendarAstronomer</code> object with the given
 * latitude and longitude.  The object's time is set to the current
 * date and time.
 * <p>
 * @param longitude The desired longitude, in <em>degrees</em> east of
 *                  the Greenwich meridian.
 *
 * @param latitude  The desired latitude, in <em>degrees</em>.  Positive
 *                  values signify North, negative South.
 *
 * @see java.util.Date#getTime()
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
CalendarAstronomer::CalendarAstronomer(double longitude, double latitude) :
  fTime(Calendar::getNow()), moonPosition(NULL) {
  fLongitude = normPI(longitude * DEG_RAD);
  fLatitude  = normPI(latitude  * DEG_RAD);
  fGmtOffset = (double)(fLongitude * 24 * HOUR_MS / CalendarAstronomer::PI2);
}
    
CalendarAstronomer::~CalendarAstronomer()
{
  delete moonPosition;
}
    
//-------------------------------------------------------------------------
// Time and date getters and setters
//-------------------------------------------------------------------------
    
    /**
     * Set the current date and time of this <code>CalendarAstronomer</code> object.  All
     * astronomical calculations are performed based on this time setting.
     *
     * @param aTime the date and time, expressed as the number of milliseconds since
     *              1/1/1970 0:00 GMT (Gregorian).
     *
     * @see #setDate
     * @see #getTime
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
void CalendarAstronomer::setTime(UDate aTime) {
  fTime = aTime;
  U_DEBUG_ASTRO_MSG(("setTime(%.1lf, %sL)\n", aTime, debug_astro_date(aTime+fGmtOffset)));
  clearCache();
}

/**
 * Set the current date and time of this <code>CalendarAstronomer</code> object.  All
 * astronomical calculations are performed based on this time setting.
 *
 * @param jdn   the desired time, expressed as a "julian day number",
 *              which is the number of elapsed days since 
 *              1/1/4713 BC (Julian), 12:00 GMT.  Note that julian day
 *              numbers start at <em>noon</em>.  To get the jdn for
 *              the corresponding midnight, subtract 0.5.
 *
 * @see #getJulianDay
 * @see #JULIAN_EPOCH_MS
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
void CalendarAstronomer::setJulianDay(double jdn) {
  fTime = (double)(jdn * DAY_MS) + JULIAN_EPOCH_MS;
  clearCache();
  julianDay = jdn;
}

/**
 * Get the current time of this <code>CalendarAstronomer</code> object,
 * represented as the number of milliseconds since
 * 1/1/1970 AD 0:00 GMT (Gregorian).
 *
 * @see #setTime
 * @see #getDate
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
UDate CalendarAstronomer::getTime() {
  return fTime;
}
    
/**
 * Get the current time of this <code>CalendarAstronomer</code> object,
 * expressed as a "julian day number", which is the number of elapsed
 * days since 1/1/4713 BC (Julian), 12:00 GMT.
 *
 * @see #setJulianDay
 * @see #JULIAN_EPOCH_MS
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
double CalendarAstronomer::getJulianDay() {
  if (julianDay == INVALID) {
    julianDay = (fTime - (double)JULIAN_EPOCH_MS) / (double)DAY_MS;
  }
  return julianDay;
}
    
/**
     * Return this object's time expressed in julian centuries:
     * the number of centuries after 1/1/1900 AD, 12:00 GMT
     *
     * @see #getJulianDay
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
double CalendarAstronomer::getJulianCentury() {
  if (julianCentury == INVALID) {
    julianCentury = (getJulianDay() - 2415020.0) / 36525;
  }
  return julianCentury;
}

/**
     * Returns the current Greenwich sidereal time, measured in hours
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
double CalendarAstronomer::getGreenwichSidereal() {
  if (siderealTime == INVALID) {
    // See page 86 of "Practial Astronomy with your Calculator",
    // by Peter Duffet-Smith, for details on the algorithm.
                
    double UT = normalize((double)fTime/HOUR_MS, 24);
        
    siderealTime = normalize(getSiderealOffset() + UT*1.002737909, 24);
  }
  return siderealTime;
}
    
double CalendarAstronomer::getSiderealOffset() {
  if (siderealT0 == INVALID) {
    double JD  = uprv_floor(getJulianDay() - 0.5) + 0.5;
    double S   = JD - 2451545.0;
    double T   = S / 36525.0;
    siderealT0 = normalize(6.697374558 + 2400.051336*T + 0.000025862*T*T, 24);
  }
  return siderealT0;
}
    
/**
     * Returns the current local sidereal time, measured in hours
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
double CalendarAstronomer::getLocalSidereal() {
  return normalize(getGreenwichSidereal() + (double)fGmtOffset/HOUR_MS, 24);
}
    
/**
     * Converts local sidereal time to Universal Time.
     *
     * @param lst   The Local Sidereal Time, in hours since sidereal midnight
     *              on this object's current date.
     *
     * @return      The corresponding Universal Time, in milliseconds since
     *              1 Jan 1970, GMT.  
     */
double CalendarAstronomer::lstToUT(double lst) {
  // Convert to local mean time
  double lt = normalize((lst - getSiderealOffset()) * 0.9972695663, 24);
        
  // Then find local midnight on this day
  double base = (DAY_MS * Math::floorDivide(fTime + fGmtOffset,DAY_MS)) - fGmtOffset;
        
  //out("    lt  =" + lt + " hours");
  //out("    base=" + new Date(base));
        
  return base + (long)(lt * HOUR_MS);
}
    
    
//-------------------------------------------------------------------------
// Coordinate transformations, all based on the current time of this object
//-------------------------------------------------------------------------

    /**
     * Convert from ecliptic to equatorial coordinates.
     *
     * @param ecliptic  A point in the sky in ecliptic coordinates.
     * @return          The corresponding point in equatorial coordinates.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
CalendarAstronomer::Equatorial* CalendarAstronomer::eclipticToEquatorial(CalendarAstronomer::Ecliptic& ecliptic)
{
  return eclipticToEquatorial(ecliptic.longitude, ecliptic.latitude);
}

/**
     * Convert from ecliptic to equatorial coordinates.
     *
     * @param eclipLong     The ecliptic longitude
     * @param eclipLat      The ecliptic latitude
     *
     * @return              The corresponding point in equatorial coordinates.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
CalendarAstronomer::Equatorial* CalendarAstronomer::eclipticToEquatorial(double eclipLong, double eclipLat)
{
  // See page 42 of "Practial Astronomy with your Calculator",
  // by Peter Duffet-Smith, for details on the algorithm.

  double obliq = eclipticObliquity();
  double sinE = ::sin(obliq);
  double cosE = cos(obliq);
        
  double sinL = ::sin(eclipLong);
  double cosL = cos(eclipLong);
        
  double sinB = ::sin(eclipLat);
  double cosB = cos(eclipLat);
  double tanB = tan(eclipLat);
        
  return new Equatorial(atan2(sinL*cosE - tanB*sinE, cosL),
                        asin(sinB*cosE + cosB*sinE*sinL) );
}

/**
     * Convert from ecliptic longitude to equatorial coordinates.
     *
     * @param eclipLong     The ecliptic longitude
     *
     * @return              The corresponding point in equatorial coordinates.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
CalendarAstronomer::Equatorial* CalendarAstronomer::eclipticToEquatorial(double eclipLong)
{
  return eclipticToEquatorial(eclipLong, 0);  // TODO: optimize
}

/**
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
CalendarAstronomer::Horizon* CalendarAstronomer::eclipticToHorizon(double eclipLong)
{
  Equatorial* equatorial = eclipticToEquatorial(eclipLong);
        
  double H = getLocalSidereal()*CalendarAstronomer::PI/12 - equatorial->ascension;     // Hour-angle
        
  double sinH = ::sin(H);
  double cosH = cos(H);
  double sinD = ::sin(equatorial->declination);
  double cosD = cos(equatorial->declination);
  double sinL = ::sin(fLatitude);
  double cosL = cos(fLatitude);
        
  double altitude = asin(sinD*sinL + cosD*cosL*cosH);
  double azimuth  = atan2(-cosD*cosL*sinH, sinD - sinL * ::sin(altitude));

  delete equatorial;
  return new Horizon(azimuth, altitude);
}

    
//-------------------------------------------------------------------------
// The Sun
//-------------------------------------------------------------------------

    //
    // Parameters of the Sun's orbit as of the epoch Jan 0.0 1990
    // Angles are in radians (after multiplying by CalendarAstronomer::PI/180)
    //
const double CalendarAstronomer::JD_EPOCH = 2447891.5; // Julian day of epoch

const double CalendarAstronomer::SUN_ETA_G   = 279.403303 * CalendarAstronomer::PI/180; // Ecliptic longitude at epoch
const double CalendarAstronomer::SUN_OMEGA_G = 282.768422 * CalendarAstronomer::PI/180; // Ecliptic longitude of perigee
const double CalendarAstronomer::SUN_E      =   0.016713;          // Eccentricity of orbit
//double sunR0     =   1.495585e8;        // Semi-major axis in KM
//double sunTheta0 =   0.533128 * CalendarAstronomer::PI/180; // Angular diameter at R0

    // The following three methods, which compute the sun parameters
    // given above for an arbitrary epoch (whatever time the object is
    // set to), make only a small difference as compared to using the
    // above constants.  E.g., Sunset times might differ by ~12
    // seconds.  Furthermore, the eta-g computation is befuddled by
    // Duffet-Smith's incorrect coefficients (p.86).  I've corrected
    // the first-order coefficient but the others may be off too - no
    // way of knowing without consulting another source.

//  /**
//   * Return the sun's ecliptic longitude at perigee for the current time.
//   * See Duffett-Smith, p. 86.
//   * @return radians
//   */
//  private double getSunOmegaG() {
//      double T = getJulianCentury();
//      return (281.2208444 + (1.719175 + 0.000452778*T)*T) * DEG_RAD;
//  }

//  /**
//   * Return the sun's ecliptic longitude for the current time.
//   * See Duffett-Smith, p. 86.
//   * @return radians
//   */
//  private double getSunEtaG() {
//      double T = getJulianCentury();
//      //return (279.6966778 + (36000.76892 + 0.0003025*T)*T) * DEG_RAD;
//      //
//      // The above line is from Duffett-Smith, and yields manifestly wrong
//      // results.  The below constant is derived empirically to match the
//      // constant he gives for the 1990 EPOCH.
//      //
//      return (279.6966778 + (-0.3262541582718024 + 0.0003025*T)*T) * DEG_RAD;
//  }

//  /**
//   * Return the sun's eccentricity of orbit for the current time.
//   * See Duffett-Smith, p. 86.
//   * @return double
//   */
//  private double getSunE() {
//      double T = getJulianCentury();
//      return 0.01675104 - (0.0000418 + 0.000000126*T)*T;
//  }

    /**
     * The longitude of the sun at the time specified by this object.
     * The longitude is measured in radians along the ecliptic
     * from the "first point of Aries," the point at which the ecliptic
     * crosses the earth's equatorial plane at the vernal equinox.
     * <p>
     * Currently, this method uses an approximation of the two-body Kepler's
     * equation for the earth and the sun.  It does not take into account the
     * perturbations caused by the other planets, the moon, etc.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
double CalendarAstronomer::getSunLongitude()
{
  // See page 86 of "Practial Astronomy with your Calculator",
  // by Peter Duffet-Smith, for details on the algorithm.
        
  if (sunLongitude == INVALID) {
    getSunLongitude(getJulianDay(), sunLongitude, meanAnomalySun);
  }
  return sunLongitude;
}
  
/**
     * TODO Make this public when the entire class is package-private.
     */
/*public*/ void CalendarAstronomer::getSunLongitude(double julianDay, double &longitude, double &meanAnomaly)
{
  // See page 86 of "Practial Astronomy with your Calculator",
  // by Peter Duffet-Smith, for details on the algorithm.
        
  double day = julianDay - JD_EPOCH;       // Days since epoch
        
  // Find the angular distance the sun in a fictitious
  // circular orbit has travelled since the epoch.
  double epochAngle = norm2PI(PI2/TROPICAL_YEAR*day);
        
        // The epoch wasn't at the sun's perigee; find the angular distance
        // since perigee, which is called the "mean anomaly"
  meanAnomaly = norm2PI(epochAngle + SUN_ETA_G - SUN_OMEGA_G);
        
  // Now find the "true anomaly", e.g. the real solar longitude
  // by solving Kepler's equation for an elliptical orbit
  // NOTE: The 3rd ed. of the book lists omega_g and eta_g in different
  // equations; omega_g is to be correct.
  longitude =  norm2PI(trueAnomaly(meanAnomaly, SUN_E) + SUN_OMEGA_G);
}

/**
     * The position of the sun at this object's current date and time,
     * in equatorial coordinates.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
CalendarAstronomer::Equatorial* CalendarAstronomer::getSunPosition() {
  return eclipticToEquatorial(getSunLongitude(), 0);
}

    
/**
     * Constant representing the vernal equinox.
     * For use with {@link #getSunTime getSunTime}. 
     * Note: In this case, "vernal" refers to the northern hemisphere's seasons.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const CalendarAstronomer::SolarLongitude CalendarAstronomer::VERNAL_EQUINOX  =  CalendarAstronomer::SolarLongitude(0);
    
/**
     * Constant representing the summer solstice.
     * For use with {@link #getSunTime getSunTime}.
     * Note: In this case, "summer" refers to the northern hemisphere's seasons.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const CalendarAstronomer::SolarLongitude CalendarAstronomer::SUMMER_SOLSTICE =  CalendarAstronomer::SolarLongitude(PI/2);
    
/**
     * Constant representing the autumnal equinox.
     * For use with {@link #getSunTime getSunTime}.
     * Note: In this case, "autumn" refers to the northern hemisphere's seasons.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const CalendarAstronomer::SolarLongitude CalendarAstronomer::AUTUMN_EQUINOX  =  CalendarAstronomer::SolarLongitude(PI);
    
/**
     * Constant representing the winter solstice.
     * For use with {@link #getSunTime getSunTime}.
     * Note: In this case, "winter" refers to the northern hemisphere's seasons.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
const CalendarAstronomer::SolarLongitude CalendarAstronomer::WINTER_SOLSTICE =  CalendarAstronomer::SolarLongitude((PI*3)/2);
    
/**
     * Find the next time at which the sun's ecliptic longitude will have
     * the desired value.  
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
class SunTimeAngleFunc : public CalendarAstronomer::AngleFunc {
public:
  virtual double eval(CalendarAstronomer& a) { return a.getSunLongitude(); }
};

UDate CalendarAstronomer::getSunTime(double desired, UBool next)
{
  SunTimeAngleFunc func;
  return timeOfAngle( func,
                      desired,
                      TROPICAL_YEAR,
                      MINUTE_MS,
                      next);
}
    
/**
     * Find the next time at which the sun's ecliptic longitude will have
     * the desired value.  
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
UDate CalendarAstronomer::getSunTime(const SolarLongitude& desired, UBool next) {
  return getSunTime(desired.value, next);
}

class RiseSetCoordFunc : public CalendarAstronomer::CoordFunc {
public:
  virtual CalendarAstronomer::Equatorial* eval(CalendarAstronomer&a) { return a.getSunPosition(); }
};

UDate CalendarAstronomer::getSunRiseSet(UBool rise)
{
  UDate t0 = fTime;

  // Make a rough guess: 6am or 6pm local time on the current day
  double noon = Math::floorDivide(fTime + fGmtOffset, DAY_MS)*DAY_MS - fGmtOffset + (12*HOUR_MS);
        
  U_DEBUG_ASTRO_MSG(("Noon=%.2lf, %sL, gmtoff %.2lf\n", noon, debug_astro_date(noon+fGmtOffset), fGmtOffset));
  setTime(noon +  ((rise ? -6 : 6) * HOUR_MS));
  U_DEBUG_ASTRO_MSG(("added %.2lf ms as a guess,\n", ((rise ? -6. : 6.) * HOUR_MS)));

  RiseSetCoordFunc func;
  double t = riseOrSet(func,
                       rise,
                       .533 * DEG_RAD,        // Angular Diameter
                       34. /60.0 * DEG_RAD,    // Refraction correction
                       MINUTE_MS / 12.);       // Desired accuracy

  setTime(t0);
  return t;
}

// Commented out - currently unused. ICU 2.6, Alan
//    //-------------------------------------------------------------------------
//    // Alternate Sun Rise/Set
//    // See Duffett-Smith p.93
//    //-------------------------------------------------------------------------
//
//    // This yields worse results (as compared to USNO data) than getSunRiseSet().
//    /**
//     * TODO Make this when the entire class is package-private.
//     */
//    /*public*/ long getSunRiseSet2(boolean rise) {
//        // 1. Calculate coordinates of the sun's center for midnight
//        double jd = uprv_floor(getJulianDay() - 0.5) + 0.5;
//        double[] sl = getSunLongitude(jd);//        double lambda1 = sl[0];
//        Equatorial pos1 = eclipticToEquatorial(lambda1, 0);
//
//        // 2. Add ... to lambda to get position 24 hours later
//        double lambda2 = lambda1 + 0.985647*DEG_RAD;
//        Equatorial pos2 = eclipticToEquatorial(lambda2, 0);
//
//        // 3. Calculate LSTs of rising and setting for these two positions
//        double tanL = ::tan(fLatitude);
//        double H = ::acos(-tanL * ::tan(pos1.declination));
//        double lst1r = (PI2 + pos1.ascension - H) * 24 / CalendarAstronomer::PI2;
//        double lst1s = (pos1.ascension + H) * 24 / CalendarAstronomer::PI2;
//               H = ::acos(-tanL * ::tan(pos2.declination));
//        double lst2r = (PI2-H + pos2.ascension ) * 24 / CalendarAstronomer::PI2;
//        double lst2s = (H + pos2.ascension ) * 24 / CalendarAstronomer::PI2;
//        if (lst1r > 24) lst1r -= 24;
//        if (lst1s > 24) lst1s -= 24;
//        if (lst2r > 24) lst2r -= 24;
//        if (lst2s > 24) lst2s -= 24;
//        
//        // 4. Convert LSTs to GSTs.  If GST1 > GST2, add 24 to GST2.
//        double gst1r = lstToGst(lst1r);
//        double gst1s = lstToGst(lst1s);
//        double gst2r = lstToGst(lst2r);
//        double gst2s = lstToGst(lst2s);
//        if (gst1r > gst2r) gst2r += 24;
//        if (gst1s > gst2s) gst2s += 24;
//
//        // 5. Calculate GST at 0h UT of this date
//        double t00 = utToGst(0);
//        
//        // 6. Calculate GST at 0h on the observer's longitude
//        double offset = ::round(fLongitude*12/PI); // p.95 step 6; he _rounds_ to nearest 15 deg.
//        double t00p = t00 - offset*1.002737909;
//        if (t00p < 0) t00p += 24; // do NOT normalize
//        
//        // 7. Adjust
//        if (gst1r < t00p) {
//            gst1r += 24;
//            gst2r += 24;
//        }
//        if (gst1s < t00p) {
//            gst1s += 24;
//            gst2s += 24;
//        }
//
//        // 8.
//        double gstr = (24.07*gst1r-t00*(gst2r-gst1r))/(24.07+gst1r-gst2r);
//        double gsts = (24.07*gst1s-t00*(gst2s-gst1s))/(24.07+gst1s-gst2s);
//
//        // 9. Correct for parallax, refraction, and sun's diameter
//        double dec = (pos1.declination + pos2.declination) / 2;
//        double psi = ::acos(sin(fLatitude) / cos(dec));
//        double x = 0.830725 * DEG_RAD; // parallax+refraction+diameter
//        double y = ::asin(sin(x) / ::sin(psi)) * RAD_DEG;
//        double delta_t = 240 * y / cos(dec) / 3600; // hours
//
//        // 10. Add correction to GSTs, subtract from GSTr
//        gstr -= delta_t;
//        gsts += delta_t;
//
//        // 11. Convert GST to UT and then to local civil time
//        double ut = gstToUt(rise ? gstr : gsts);
//        //System.out.println((rise?"rise=":"set=") + ut + ", delta_t=" + delta_t);
//        long midnight = DAY_MS * (time / DAY_MS); // Find UT midnight on this day
//        return midnight + (long) (ut * 3600000);
//    }

// Commented out - currently unused. ICU 2.6, Alan
//    /**
//     * Convert local sidereal time to Greenwich sidereal time.
//     * Section 15.  Duffett-Smith p.21
//     * @param lst in hours (0..24)
//     * @return GST in hours (0..24)
//     */
//    double lstToGst(double lst) {
//        double delta = fLongitude * 24 / CalendarAstronomer::PI2;
//        return normalize(lst - delta, 24);
//    }
 
// Commented out - currently unused. ICU 2.6, Alan
//    /**
//     * Convert UT to GST on this date.
//     * Section 12.  Duffett-Smith p.17
//     * @param ut in hours
//     * @return GST in hours
//     */
//    double utToGst(double ut) {
//        return normalize(getT0() + ut*1.002737909, 24);
//    }

// Commented out - currently unused. ICU 2.6, Alan
//    /**
//     * Convert GST to UT on this date.
//     * Section 13.  Duffett-Smith p.18
//     * @param gst in hours
//     * @return UT in hours
//     */
//    double gstToUt(double gst) {
//        return normalize(gst - getT0(), 24) * 0.9972695663;
//    }

// Commented out - currently unused. ICU 2.6, Alan
//    double getT0() {
//        // Common computation for UT <=> GST
//
//        // Find JD for 0h UT
//        double jd = uprv_floor(getJulianDay() - 0.5) + 0.5;
//
//        double s = jd - 2451545.0;
//        double t = s / 36525.0;
//        double t0 = 6.697374558 + (2400.051336 + 0.000025862*t)*t;
//        return t0;
//    }

// Commented out - currently unused. ICU 2.6, Alan
//    //-------------------------------------------------------------------------
//    // Alternate Sun Rise/Set
//    // See sci.astro FAQ
//    // http://www.faqs.org/faqs/astronomy/faq/part3/section-5.html
//    //-------------------------------------------------------------------------
//
//    // Note: This method appears to produce inferior accuracy as
//    // compared to getSunRiseSet(). 
//
//    /**
//     * TODO Make this when the entire class is package-private.
//     */
//    /*public*/ long getSunRiseSet3(boolean rise) {
//
//        // Compute day number for 0.0 Jan 2000 epoch
//        double d = (double)(time - EPOCH_2000_MS) / DAY_MS;
//
//        // Now compute the Local Sidereal Time, LST:
//        // 
//        double LST  =  98.9818  +  0.985647352 * d  +  /*UT*15  +  long*/
//            fLongitude*RAD_DEG;
//        // 
//        // (east long. positive).  Note that LST is here expressed in degrees,
//        // where 15 degrees corresponds to one hour.  Since LST really is an angle,
//        // it's convenient to use one unit---degrees---throughout.
//
//        // 	COMPUTING THE SUN'S POSITION
//        // 	----------------------------
//        // 
//        // To be able to compute the Sun's rise/set times, you need to be able to
//        // compute the Sun's position at any time.  First compute the "day
//        // number" d as outlined above, for the desired moment.  Next compute:
//        // 
//        double oblecl = 23.4393 - 3.563E-7 * d;
//        // 
//        double w  =  282.9404  +  4.70935E-5   * d;
//        double M  =  356.0470  +  0.9856002585 * d;
//        double e  =  0.016709  -  1.151E-9     * d;
//        // 
//        // This is the obliquity of the ecliptic, plus some of the elements of
//        // the Sun's apparent orbit (i.e., really the Earth's orbit): w =
//        // argument of perihelion, M = mean anomaly, e = eccentricity.
//        // Semi-major axis is here assumed to be exactly 1.0 (while not strictly
//        // true, this is still an accurate approximation).  Next compute E, the
//        // eccentric anomaly:
//        // 
//        double E = M + e*(180/PI) * ::sin(M*DEG_RAD) * ( 1.0 + e*cos(M*DEG_RAD) );
//        // 
//        // where E and M are in degrees.  This is it---no further iterations are
//        // needed because we know e has a sufficiently small value.  Next compute
//        // the true anomaly, v, and the distance, r:
//        // 
//        /*      r * cos(v)  =  */ double A  =  cos(E*DEG_RAD) - e;
//        /*      r * ::sin(v)  =  */ double B  =  ::sqrt(1 - e*e) * ::sin(E*DEG_RAD);
//        // 
//        // and
//        // 
//        //      r  =  sqrt( A*A + B*B )
//        double v  =  ::atan2( B, A )*RAD_DEG;
//        // 
//        // The Sun's true longitude, slon, can now be computed:
//        // 
//        double slon  =  v + w;
//        // 
//        // Since the Sun is always at the ecliptic (or at least very very close to
//        // it), we can use simplified formulae to convert slon (the Sun's ecliptic
//        // longitude) to sRA and sDec (the Sun's RA and Dec):
//        // 
//        //                   ::sin(slon) * cos(oblecl)
//        //     tan(sRA)  =  -------------------------
//        // 			cos(slon)
//        // 
//        //     ::sin(sDec) =  ::sin(oblecl) * ::sin(slon)
//        // 
//        // As was the case when computing az, the Azimuth, if possible use an
//        // atan2() function to compute sRA.
//
//        double sRA = ::atan2(sin(slon*DEG_RAD) * cos(oblecl*DEG_RAD), cos(slon*DEG_RAD))*RAD_DEG;
//
//        double sin_sDec = ::sin(oblecl*DEG_RAD) * ::sin(slon*DEG_RAD);
//        double sDec = ::asin(sin_sDec)*RAD_DEG;
//
//        // 	COMPUTING RISE AND SET TIMES
//        // 	----------------------------
//        // 
//        // To compute when an object rises or sets, you must compute when it
//        // passes the meridian and the HA of rise/set.  Then the rise time is
//        // the meridian time minus HA for rise/set, and the set time is the
//        // meridian time plus the HA for rise/set.
//        // 
//        // To find the meridian time, compute the Local Sidereal Time at 0h local
//        // time (or 0h UT if you prefer to work in UT) as outlined above---name
//        // that quantity LST0.  The Meridian Time, MT, will now be:
//        // 
//        //     MT  =  RA - LST0
//        double MT = normalize(sRA - LST, 360);
//        // 
//        // where "RA" is the object's Right Ascension (in degrees!).  If negative,
//        // add 360 deg to MT.  If the object is the Sun, leave the time as it is,
//        // but if it's stellar, multiply MT by 365.2422/366.2422, to convert from
//        // sidereal to solar time.  Now, compute HA for rise/set, name that
//        // quantity HA0:
//        // 
//        //                 ::sin(h0)  -  ::sin(lat) * ::sin(Dec)
//        // cos(HA0)  =  ---------------------------------
//        //                      cos(lat) * cos(Dec)
//        // 
//        // where h0 is the altitude selected to represent rise/set.  For a purely
//        // mathematical horizon, set h0 = 0 and simplify to:
//        // 
//        // 	cos(HA0)  =  - tan(lat) * tan(Dec)
//        // 
//        // If you want to account for refraction on the atmosphere, set h0 = -35/60
//        // degrees (-35 arc minutes), and if you want to compute the rise/set times
//        // for the Sun's upper limb, set h0 = -50/60 (-50 arc minutes).
//        // 
//        double h0 = -50/60 * DEG_RAD;
//
//        double HA0 = ::acos(
//          (sin(h0) - ::sin(fLatitude) * sin_sDec) /
//          (cos(fLatitude) * cos(sDec*DEG_RAD)))*RAD_DEG;
//
//        // When HA0 has been computed, leave it as it is for the Sun but multiply
//        // by 365.2422/366.2422 for stellar objects, to convert from sidereal to
//        // solar time.  Finally compute:
//        // 
//        //    Rise time  =  MT - HA0
//        //    Set  time  =  MT + HA0
//        // 
//        // convert the times from degrees to hours by dividing by 15.
//        // 
//        // If you'd like to check that your calculations are accurate or just
//        // need a quick result, check the USNO's Sun or Moon Rise/Set Table,
//        // <URL:http://aa.usno.navy.mil/AA/data/docs/RS_OneYear.html>.
//
//        double result = MT + (rise ? -HA0 : HA0); // in degrees
//
//        // Find UT midnight on this day
//        long midnight = DAY_MS * (time / DAY_MS);
//
//        return midnight + (long) (result * 3600000 / 15);
//    }

    //-------------------------------------------------------------------------
    // The Moon
    //-------------------------------------------------------------------------
    
const double CalendarAstronomer::moonL0 = 318.351648 * CalendarAstronomer::PI/180;   // Mean long. at epoch
const double CalendarAstronomer::moonP0 =  36.340410 * CalendarAstronomer::PI/180;   // Mean long. of perigee
const double CalendarAstronomer::moonN0 = 318.510107 * CalendarAstronomer::PI/180;   // Mean long. of node
const double CalendarAstronomer::moonI  =   5.145366 * CalendarAstronomer::PI/180;   // Inclination of orbit
const double CalendarAstronomer::moonE  =   0.054900;            // Eccentricity of orbit
    
// These aren't used right now
const double CalendarAstronomer::moonA  =   3.84401e5;           // semi-major axis (km)
const double CalendarAstronomer::moonT0 =   0.5181 * CalendarAstronomer::PI/180;     // Angular size at distance A
const double CalendarAstronomer::moonPi =   0.9507 * CalendarAstronomer::PI/180;     // Parallax at distance A
    
/**
     * The position of the moon at the time set on this
     * object, in equatorial coordinates.
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
CalendarAstronomer::Equatorial* CalendarAstronomer::getMoonPosition()
{
  //
  // See page 142 of "Practial Astronomy with your Calculator",
  // by Peter Duffet-Smith, for details on the algorithm.
  //
  if (moonPosition == NULL) {
    // Calculate the solar longitude.  Has the side effect of
    // filling in "meanAnomalySun" as well.
    double sunLongitude = getSunLongitude();
            
    //
    // Find the # of days since the epoch of our orbital parameters.
    // TODO: Convert the time of day portion into ephemeris time
    //
    double day = getJulianDay() - JD_EPOCH;       // Days since epoch
            
    // Calculate the mean longitude and anomaly of the moon, based on
    // a circular orbit.  Similar to the corresponding solar calculation.
    double meanLongitude = norm2PI(13.1763966*PI/180*day + moonL0);
    double meanAnomalyMoon = norm2PI(meanLongitude - 0.1114041*PI/180 * day - moonP0);
            
    //
    // Calculate the following corrections:
    //  Evection:   the sun's gravity affects the moon's eccentricity
    //  Annual Eqn: variation in the effect due to earth-sun distance
    //  A3:         correction factor (for ???)
    //
    double evection = 1.2739*PI/180 * ::sin(2 * (meanLongitude - sunLongitude)
                                            - meanAnomalyMoon);
    double annual   = 0.1858*PI/180 * ::sin(meanAnomalySun);
    double a3       = 0.3700*PI/180 * ::sin(meanAnomalySun);

    meanAnomalyMoon += evection - annual - a3;
            
    //
    // More correction factors:
    //  center  equation of the center correction
    //  a4      yet another error correction (???)
    //
    // TODO: Skip the equation of the center correction and solve Kepler's eqn?
    //
    double center = 6.2886*PI/180 * ::sin(meanAnomalyMoon);
    double a4 =     0.2140*PI/180 * ::sin(2 * meanAnomalyMoon);
            
    // Now find the moon's corrected longitude
    moonLongitude = meanLongitude + evection + center - annual + a4;

    //
    // And finally, find the variation, caused by the fact that the sun's
    // gravitational pull on the moon varies depending on which side of
    // the earth the moon is on
    //
    double variation = 0.6583*CalendarAstronomer::PI/180 * ::sin(2*(moonLongitude - sunLongitude));
            
    moonLongitude += variation;
            
    //
    // What we've calculated so far is the moon's longitude in the plane
    // of its own orbit.  Now map to the ecliptic to get the latitude
    // and longitude.  First we need to find the longitude of the ascending
    // node, the position on the ecliptic where it is crossed by the moon's
    // orbit as it crosses from the southern to the northern hemisphere.
    //
    double nodeLongitude = norm2PI(moonN0 - 0.0529539*PI/180 * day);

    nodeLongitude -= 0.16*PI/180 * ::sin(meanAnomalySun);

    double y = ::sin(moonLongitude - nodeLongitude);
    double x = cos(moonLongitude - nodeLongitude);
            
    moonEclipLong = ::atan2(y*cos(moonI), x) + nodeLongitude;
    double moonEclipLat = ::asin(y * ::sin(moonI));

    moonPosition = eclipticToEquatorial(moonEclipLong, moonEclipLat);
  }
  return moonPosition;
}
    
/**
 * The "age" of the moon at the time specified in this object.
 * This is really the angle between the
 * current ecliptic longitudes of the sun and the moon,
 * measured in radians.
 *
 * @see #getMoonPhase
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
double CalendarAstronomer::getMoonAge() {
  // See page 147 of "Practial Astronomy with your Calculator",
  // by Peter Duffet-Smith, for details on the algorithm.
  //
  // Force the moon's position to be calculated.  We're going to use
  // some the intermediate results cached during that calculation.
  //
  getMoonPosition();
        
  return norm2PI(moonEclipLong - sunLongitude);
}
    
/**
 * Calculate the phase of the moon at the time set in this object.
 * The returned phase is a <code>double</code> in the range
 * <code>0 <= phase < 1</code>, interpreted as follows:
 * <ul>
 * <li>0.00: New moon
 * <li>0.25: First quarter
 * <li>0.50: Full moon
 * <li>0.75: Last quarter
 * </ul>
 *
 * @see #getMoonAge
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
double CalendarAstronomer::getMoonPhase() {
  // See page 147 of "Practial Astronomy with your Calculator",
  // by Peter Duffet-Smith, for details on the algorithm.
  return 0.5 * (1 - cos(getMoonAge()));
}
    
/**
 * Constant representing a new moon.
 * For use with {@link #getMoonTime getMoonTime}
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
const CalendarAstronomer::MoonAge CalendarAstronomer::NEW_MOON      =  CalendarAstronomer::MoonAge(0);

/**
 * Constant representing the moon's first quarter.
 * For use with {@link #getMoonTime getMoonTime}
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
const CalendarAstronomer::MoonAge CalendarAstronomer::FIRST_QUARTER =  CalendarAstronomer::MoonAge(CalendarAstronomer::PI/2);
    
/**
 * Constant representing a full moon.
 * For use with {@link #getMoonTime getMoonTime}
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
const CalendarAstronomer::MoonAge CalendarAstronomer::FULL_MOON     =  CalendarAstronomer::MoonAge(CalendarAstronomer::PI);
    
/**
 * Constant representing the moon's last quarter.
 * For use with {@link #getMoonTime getMoonTime}
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */

class MoonTimeAngleFunc : public CalendarAstronomer::AngleFunc {
public:
  virtual double eval(CalendarAstronomer&a) { return a.getMoonAge(); }
};

const CalendarAstronomer::MoonAge CalendarAstronomer::LAST_QUARTER  =  CalendarAstronomer::MoonAge((CalendarAstronomer::PI*3)/2);

/**
 * Find the next or previous time at which the Moon's ecliptic
 * longitude will have the desired value.  
 * <p>
 * @param desired   The desired longitude.
 * @param next      <tt>true</tt> if the next occurrance of the phase
 *                  is desired, <tt>false</tt> for the previous occurrance. 
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
UDate CalendarAstronomer::getMoonTime(double desired, UBool next)
{
  MoonTimeAngleFunc func;
  return timeOfAngle( func,
                      desired,
                      SYNODIC_MONTH,
                      MINUTE_MS,
                      next);
}
    
/**
 * Find the next or previous time at which the moon will be in the
 * desired phase.
 * <p>
 * @param desired   The desired phase of the moon.
 * @param next      <tt>true</tt> if the next occurrance of the phase
 *                  is desired, <tt>false</tt> for the previous occurrance. 
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
UDate CalendarAstronomer::getMoonTime(CalendarAstronomer::MoonAge desired, UBool next) {
  return getMoonTime(desired.value, next);
}
   
class MoonRiseSetCoordFunc : public CalendarAstronomer::CoordFunc {
public:
  virtual CalendarAstronomer::Equatorial* eval(CalendarAstronomer&a) { return a.getMoonPosition(); }
};
 
/**
 * Returns the time (GMT) of sunrise or sunset on the local date to which
 * this calendar is currently set.
 * @internal
 * @deprecated ICU 2.4. This class may be removed or modified.
 */
UDate CalendarAstronomer::getMoonRiseSet(UBool rise)
{
  MoonRiseSetCoordFunc func;
  return riseOrSet(func,
                   rise,
                   .533 * DEG_RAD,        // Angular Diameter
                   34 /60.0 * DEG_RAD,    // Refraction correction
                   MINUTE_MS);            // Desired accuracy
}

//-------------------------------------------------------------------------
// Interpolation methods for finding the time at which a given event occurs
//-------------------------------------------------------------------------
    
UDate CalendarAstronomer::timeOfAngle(AngleFunc& func, double desired,
                                      double periodDays, double epsilon, UBool next)
{
  // Find the value of the function at the current time
  double lastAngle = func.eval(*this);
        
  // Find out how far we are from the desired angle
  double deltaAngle = norm2PI(desired - lastAngle) ;
        
  // Using the average period, estimate the next (or previous) time at
  // which the desired angle occurs.
  double deltaT =  (deltaAngle + (next ? 0 : -PI2)) * (periodDays*DAY_MS) / CalendarAstronomer::PI2;
        
  double lastDeltaT = deltaT; // Liu
  UDate startTime = fTime; // Liu
        
  setTime(fTime + (long)deltaT);

  // Now iterate until we get the error below epsilon.  Throughout
  // this loop we use normPI to get values in the range -Pi to Pi,
  // since we're using them as correction factors rather than absolute angles.
  do {
    // Evaluate the function at the time we've estimated
    double angle = func.eval(*this);

    // Find the # of milliseconds per radian at this point on the curve
    double factor = uprv_fabs(deltaT / normPI(angle-lastAngle));

    // Correct the time estimate based on how far off the angle is
    deltaT = normPI(desired - angle) * factor;
            
    // HACK:
    // 
    // If abs(deltaT) begins to diverge we need to quit this loop.
    // This only appears to happen when attempting to locate, for
    // example, a new moon on the day of the new moon.  E.g.:
    // 
    // This result is correct:
    // newMoon(7508(Mon Jul 23 00:00:00 CST 1990,false))=
    //   Sun Jul 22 10:57:41 CST 1990
    // 
    // But attempting to make the same call a day earlier causes deltaT
    // to diverge:
    // CalendarAstronomer.timeOfAngle() diverging: 1.348508727575625E9 ->
    //   1.3649828540224032E9
    // newMoon(7507(Sun Jul 22 00:00:00 CST 1990,false))=
    //   Sun Jul 08 13:56:15 CST 1990
    //
    // As a temporary solution, we catch this specific condition and
    // adjust our start time by one eighth period days (either forward
    // or backward) and try again.
    // Liu 11/9/00
    if (uprv_fabs(deltaT) > uprv_fabs(lastDeltaT)) {
      long delta = (long) (periodDays * DAY_MS / 8);
      setTime(startTime + (next ? delta : -delta));
      return timeOfAngle(func, desired, periodDays, epsilon, next);
    }

    lastDeltaT = deltaT;
    lastAngle = angle;

    setTime(fTime + (long)deltaT);
  }
  while (uprv_fabs(deltaT) > epsilon);
        
  return fTime;
}
    
UDate CalendarAstronomer::riseOrSet(CoordFunc& func, UBool rise,
                                    double diameter, double refraction, 
                                    double epsilon)
{        
  Equatorial*  pos = NULL;
  double      tanL   = ::tan(fLatitude);
  double     deltaT = 0;
  int32_t         count = 0;
        
  //
  // Calculate the object's position at the current time, then use that
  // position to calculate the time of rising or setting.  The position
  // will be different at that time, so iterate until the error is allowable.
  //
  U_DEBUG_ASTRO_MSG(("setup rise=%s, dia=%.3lf, ref=%.3lf, eps=%.3lf\n",
                     rise?"T":"F", diameter, refraction, epsilon));
  do {
    // See "Practical Astronomy With Your Calculator, section 33.
    pos = func.eval(*this);
    double angle = ::acos(-tanL * ::tan(pos->declination));
    double lst = ((rise ? CalendarAstronomer::PI2-angle : angle) + pos->ascension ) * 24 / CalendarAstronomer::PI2;
                         
    // Convert from LST to Universal Time.
    UDate newTime = lstToUT( lst );
            
    deltaT = newTime - fTime;
    setTime(newTime);
    U_DEBUG_ASTRO_MSG(("%d] dT=%.3lf, angle=%.3lf, lst=%.3lf,   A=%.3lf/D=%.3lf\n",
                       count, deltaT, angle, lst, pos->ascension, pos->declination));
  }
  while (++ count < 5 && uprv_fabs(deltaT) > epsilon);

  // Calculate the correction due to refraction and the object's angular diameter
  double cosD  = ::cos(pos->declination);
  double psi   = ::acos(sin(fLatitude) / cosD);
  double x     = diameter / 2 + refraction;
  double y     = ::asin(sin(x) / ::sin(psi));
  long  delta  = (long)((240 * y * RAD_DEG / cosD)*SECOND_MS);
        
  return fTime + (rise ? -delta : delta);
}
    
/**
     * Find the "true anomaly" (longitude) of an object from
     * its mean anomaly and the eccentricity of its orbit.  This uses
     * an iterative solution to Kepler's equation.
     *
     * @param meanAnomaly   The object's longitude calculated as if it were in
     *                      a regular, circular orbit, measured in radians
     *                      from the point of perigee.  
     *
     * @param eccentricity  The eccentricity of the orbit
     *
     * @return The true anomaly (longitude) measured in radians
     */
double CalendarAstronomer::trueAnomaly(double meanAnomaly, double eccentricity)
{
  // First, solve Kepler's equation iteratively
  // Duffett-Smith, p.90
  double delta;
  double E = meanAnomaly;
  do {
    delta = E - eccentricity * ::sin(E) - meanAnomaly;
    E = E - delta / (1 - eccentricity * ::cos(E));
  } 
  while (uprv_fabs(delta) > 1e-5); // epsilon = 1e-5 rad

  return 2.0 * ::atan( ::tan(E/2) * ::sqrt( (1+eccentricity)
                                            /(1-eccentricity) ) );
}
    
/**
     * Return the obliquity of the ecliptic (the angle between the ecliptic
     * and the earth's equator) at the current time.  This varies due to
     * the precession of the earth's axis.
     *
     * @return  the obliquity of the ecliptic relative to the equator,
     *          measured in radians.
     */
double CalendarAstronomer::eclipticObliquity() {
  if (eclipObliquity == INVALID) {
    const double epoch = 2451545.0;     // 2000 AD, January 1.5

    double T = (getJulianDay() - epoch) / 36525;
            
    eclipObliquity = 23.439292
      - 46.815/3600 * T
      - 0.0006/3600 * T*T
      + 0.00181/3600 * T*T*T;
                           
    eclipObliquity *= DEG_RAD;
  }
  return eclipObliquity;
}
    
     
//-------------------------------------------------------------------------
// Private data
//-------------------------------------------------------------------------
const double CalendarAstronomer::INVALID = DBL_MIN; // revisit

void CalendarAstronomer::clearCache() {
  julianDay       = INVALID;
  julianCentury   = INVALID;
  sunLongitude    = INVALID;
  meanAnomalySun  = INVALID;
  moonLongitude   = INVALID;
  moonEclipLong   = INVALID;
  meanAnomalyMoon = INVALID;
  eclipObliquity  = INVALID;
  siderealTime    = INVALID;
  siderealT0      = INVALID;
  delete moonPosition;
  moonPosition    = NULL;
}
    
//private static void out(String s) {
//    System.out.println(s);
//}
    
    //private static String deg(double rad) {
    //    return Double.toString(rad * RAD_DEG);
    //}
    
    //private static String hours(long ms) {
    //    return Double.toString((double)ms / HOUR_MS) + " hours";
    //}

    /**
     * @internal
     * @deprecated ICU 2.4. This class may be removed or modified.
     */
UDate CalendarAstronomer::local(UDate localMillis) {
  // TODO - srl ?
  TimeZone *tz = TimeZone::createDefault();
  int32_t rawOffset;
  int32_t dstOffset;
  UErrorCode status = U_ZERO_ERROR;
  tz->getOffset(localMillis, TRUE, rawOffset, dstOffset, status);
  delete tz;
  return localMillis - rawOffset;
}


//  static private String radToHms(double angle) {
//    int hrs = (int) (angle*RAD_HOUR);
//    int min = (int)((angle*RAD_HOUR - hrs) * 60);
//    int sec = (int)((angle*RAD_HOUR - hrs - min/60.0) * 3600);
        
//    return Integer.toString(hrs) + "h" + min + "m" + sec + "s";
//  }
    
//  static private String radToDms(double angle) {
//    int deg = (int) (angle*RAD_DEG);
//    int min = (int)((angle*RAD_DEG - deg) * 60);
//    int sec = (int)((angle*RAD_DEG - deg - min/60.0) * 3600);
  
//    return Integer.toString(deg) + "\u00b0" + min + "'" + sec + "\"";
//  }

#endif //  !UCONFIG_NO_FORMATTING