def geom_mean_long(time):
'''
Sun mean longitude (degrees)
'''
julian_cent = julian_century(time)
angle = 280.46646 + julian_cent * (julian_cent * 3.032e-4 + 36000.76983)
return angle % 360
def daytime_length(time, latitude):
'''
Length of day time (Sunlight duration) in hours.
'''
julian_cent = julian_century(time)
hour_angle = sunrise_hour_angle(time, latitude)
return 8 * hour_angle / 60
def geom_mean_anom(time):
'''
Sun Mean Anomaly (degrees)
'''
julian_cent = julian_century(time)
angle = 357.52911 + julian_cent * (35999.05029 - julian_cent * 1.537e-4)
return angle
def sunset(time, latitude, longitude):
'''
Sunset time
'''
noon = solar_noon(time, longitude)
julian_cent = julian_century(time)
hour_angle = sunrise_hour_angle(time, latitude)
delta = datetime.timedelta(minutes=4 * hour_angle)
return noon + delta
def solar_zenith(time, latitude, longitude):
'''
Solar Zenith Angle in degrees
'''
julian_cent = julian_century(time)
decn = solar_declination(time)
h_angle = hour_angle(time, longitude)
a1 = sin(radians(latitude)) * sin(radians(decn))
a2 = cos(radians(latitude)) * cos(radians(decn)) * cos(radians(h_angle))
return degrees(acos(a1 + a2))
def equation_of_center(time):
'''
Sun Equation of Center
'''
julian_cent = julian_century(time)
anom = geom_mean_anom(time)
anom = radians(anom)
t1 = sin(anom) * (1.914602 - julian_cent * (0.004817 + 1.4e-5 * julian_cent))
t2 = sin(2 * anom) * (0.019993 - 0.000101 * julian_cent)
t3 = sin(3 * anom) * 0.000289
return t1 + t2 + t3
def true_solar_time(time, longitude):
'''
True solar time in minutes from midnight
'''
utc = pytz.timezone('UTC')
julian_cent = julian_century(time)
eot = equation_of_time(time)
delta = datetime.timedelta(minutes=eot + longitude * 4)
true_time = (time + delta).astimezone(utc)
hour = true_time.hour
minute = true_time.minute
second = true_time.second
return get_minutes(true_time)
def solar_noon(time, longitude):
'''
Solar noon time
'''
tz = time.tzinfo
utc = pytz.timezone('UTC')
julian_cent = julian_century(time)
eot = equation_of_time(time)
noon_offset = (720 - 4 * longitude - eot) / 1440
base_time = datetime.time()
midnight = datetime.datetime.combine(time.date(), base_time)
midnight = utc.localize(midnight)
noon_utc = midnight + datetime.timedelta(days=noon_offset)
return noon_utc.astimezone(tz)
def solar_azimuth(time, latitude, longitude):
'''
Azimuth angle (measured Clockwise from North)
'''
julian_cent = julian_century(time)
zenith = radians(solar_zenith(time, latitude, longitude))
decln = radians(solar_declination(time))
h_angle = hour_angle(time, longitude)
lat = radians(latitude)
if h_angle > 0:
a1 = sin(lat) * cos(zenith) - sin(decln)
a2 = cos(lat) * sin(zenith)
azimuth = degrees(acos( a1 / a2)) + 180
return azimuth%360
else:
a1 = sin(lat) * cos(zenith) - sin(decln)
a2 = cos(lat) * sin(zenith)
azimuth = 540 - degrees(acos(a1 /a2))
return azimuth%360
def obeliq_corr(time):
julian_cent = julian_century(time)
moe = mean_obliq_ecliptic(time)
return moe + 0.00256 * cos(radians(125.04 - 1934.136 * julian_cent))
def mean_obliq_ecliptic(time):
julian_cent = julian_century(time)
res = 46.815 + julian_cent * (0.00059 - julian_cent * 0.001813)
res = 21.448 - julian_cent * (res)
res = 23 + (26 + res / 60) / 60
return res
def app_long(time):
julian_cent = julian_century(time)
tlon = true_longitude(time)
return tlon - 0.00569 - 0.00478 * sin(
radians(125.04 - 1934.136 * julian_cent))
def eccent_earth_orbit(time):
'''
Eccentricity of Earth orbit
'''
julian_cent = julian_century(time)
return 0.016708634 - julian_cent * (4.2037e-5 + 1.267e-7 * julian_cent)
def test_julian_century(self):
tz = pytz.timezone('Australia/Perth')
time = datetime.datetime(2010, 6, 21, 4, 45)
time = tz.localize(time)
self.assertAlmostEqual(julian_century(time), 0.10467801733972)