/* 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 );