AstTime.cxx

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//
// AstTime
//
// Package: Ast (AstTime).
//
// S. Kasahara 05/03
//
// Purpose: Provide utility routines to convert between different
//          astronomical time systems.
//

#include "AstroUtil/novas.h"
#include "AstroUtil/AstTime.h"

// Definition of methods (alphabetical order)
// ******************************************

void AstUtil::CalendarToJulian( int year, int month, int day,
                                double hour, double& juliandate ) {
  // Static method to convert from calendar date to julian date (hours)

  juliandate = julian_date(year,month,day,hour); // nova routine

}

void AstUtil::JulianToGMST( double juliandate, double& gmst ) {
  // Static method to convert from julian date (hours) to greenwich
  // mean sidereal time (hours)

  double fracjuliandate = fmod(juliandate,1.);
  double intjuliandate = juliandate - fracjuliandate;
  sidereal_time(intjuliandate,fracjuliandate,0,&gmst); // nova routine
 
}

void AstUtil::JulianToGAST( double juliandate, double& gast ) {
  // Static method to convert from julian date to greenwich
  // apparent sidereal time (hours)

  double oblm,oblt,eqeq,psi,eps;
  earthtilt(juliandate,&oblm,&oblt,&eqeq,&psi,&eps);

  double fracjuliandate = fmod(juliandate,1.);
  double intjuliandate = juliandate - fracjuliandate;
  sidereal_time(intjuliandate,fracjuliandate,eqeq,&gast); // nova routine
 
}

void AstUtil::GSTToLST(double gst,double longitude,double& lst) {
  // Static method to convert from greenwich sidereal time (hours) to local 
  // sidereal time (hours) 
  // Longitude is expressed in degrees and east of 0^o is +, west -.

  lst = gst + longitude*12./180.; // hours
  if ( lst < 0. ) lst += 24.;
  if ( lst > 24. ) lst -= 24.;
}

void AstUtil::LSTToGST(double lst,double longitude,double& gst) {
  // Static method to convert from lst to gst (hours) 
  // Longitude is expressed in degrees and east of 0^o is +, west -.

  gst = lst - longitude*12./180.; // hours
  if ( gst < 0. ) gst += 24.;
  if ( gst > 24. ) gst -= 24.;
}

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