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 `/*` `SUNRISET.H - computes Sun rise/set times, start/end of twilight, and` ` the length of the day at any date and latitude` `Written as DAYLEN.C, 1989-08-16` `Modified to SUNRISET.C, 1992-12-01` `Split to a header file, 2017-12-10, by Joachim Nilsson` `(c) Paul Schlyter, 1989, 1992` `Released to the public domain by Paul Schlyter, December 1992` `*/` ``` ``` `/* A macro to compute the number of days elapsed since 2000 Jan 0.0 */` `/* (which is equal to 1999 Dec 31, 0h UT) */` ``` ``` `#define days_since_2000_Jan_0(y,m,d) \` ` (367L*(y)-((7*((y)+(((m)+9)/12)))/4)+((275*(m))/9)+(d)-730530L)` `/* Some conversion factors between radians and degrees */` ``` ``` `#ifndef PI` ` #define PI 3.1415926535897932384` `#endif` `#define RADEG ( 180.0 / PI )` `#define DEGRAD ( PI / 180.0 )` `/* The trigonometric functions in degrees */` ``` ``` `#define sind(x) sin((x)*DEGRAD)` `#define cosd(x) cos((x)*DEGRAD)` `#define tand(x) tan((x)*DEGRAD)` `#define atand(x) (RADEG*atan(x))` `#define asind(x) (RADEG*asin(x))` `#define acosd(x) (RADEG*acos(x))` `#define atan2d(y,x) (RADEG*atan2(y,x))` ``` ``` `/* Following are some macros around the "workhorse" function __daylen__ */` `/* They mainly fill in the desired values for the reference altitude */` `/* below the horizon, and also selects whether this altitude should */` `/* refer to the Sun's center or its upper limb. */` ``` ``` ``` ``` `/* This macro computes the length of the day, from sunrise to sunset. */` `/* Sunrise/set is considered to occur when the Sun's upper limb is */` `/* 35 arc minutes below the horizon (this accounts for the refraction */` `/* of the Earth's atmosphere). */` `#define day_length(year,month,day,lon,lat) \` ` __daylen__( year, month, day, lon, lat, -35.0/60.0, 1 )` `/* This macro computes the length of the day, including civil twilight. */` `/* Civil twilight starts/ends when the Sun's center is 6 degrees below */` `/* the horizon. */` `#define day_civil_twilight_length(year,month,day,lon,lat) \` ` __daylen__( year, month, day, lon, lat, -6.0, 0 )` `/* This macro computes the length of the day, incl. nautical twilight. */` `/* Nautical twilight starts/ends when the Sun's center is 12 degrees */` `/* below the horizon. */` `#define day_nautical_twilight_length(year,month,day,lon,lat) \` ` __daylen__( year, month, day, lon, lat, -12.0, 0 )` `/* This macro computes the length of the day, incl. astronomical twilight. */` `/* Astronomical twilight starts/ends when the Sun's center is 18 degrees */` `/* below the horizon. */` `#define day_astronomical_twilight_length(year,month,day,lon,lat) \` ` __daylen__( year, month, day, lon, lat, -18.0, 0 )` ``` ``` `/* This macro computes times for sunrise/sunset. */` `/* Sunrise/set is considered to occur when the Sun's upper limb is */` `/* 35 arc minutes below the horizon (this accounts for the refraction */` `/* of the Earth's atmosphere). */` `#define sun_rise_set(year,month,day,lon,lat,rise,set) \` ` __sunriset__( year, month, day, lon, lat, -35.0/60.0, 1, rise, set )` `/* This macro computes the start and end times of civil twilight. */` `/* Civil twilight starts/ends when the Sun's center is 6 degrees below */` `/* the horizon. */` `#define civil_twilight(year,month,day,lon,lat,start,end) \` ` __sunriset__( year, month, day, lon, lat, -6.0, 0, start, end )` `/* This macro computes the start and end times of nautical twilight. */` `/* Nautical twilight starts/ends when the Sun's center is 12 degrees */` `/* below the horizon. */` `#define nautical_twilight(year,month,day,lon,lat,start,end) \` ` __sunriset__( year, month, day, lon, lat, -12.0, 0, start, end )` `/* This macro computes the start and end times of astronomical twilight. */` `/* Astronomical twilight starts/ends when the Sun's center is 18 degrees */` `/* below the horizon. */` `#define astronomical_twilight(year,month,day,lon,lat,start,end) \` ` __sunriset__( year, month, day, lon, lat, -18.0, 0, start, end )` ``` ``` `/* Function prototypes */` ``` ``` `double __daylen__( int year, int month, int day, double lon, double lat,` ` double altit, int upper_limb );` ``` ``` `int __sunriset__( int year, int month, int day, double lon, double lat,` ` double altit, int upper_limb, double *rise, double *set );` ``` ``` `void sunpos( double d, double *lon, double *r );` ``` ``` `void sun_RA_dec( double d, double *RA, double *dec, double *r );` ``` ``` `double revolution( double x );` ``` ``` `double rev180( double x );` ``` ``` ```double GMST0( double d ); ``` ``` ```