m + wrap doc

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 213 insertions, 107 deletions

diff --git a/src/solar.py b/src/solar.py
index ead1653..b14ed47 100644
--- a/src/solar.py
+++ b/src/solar.py
@@ -23,42 +23,50 @@ import time
 
 SOLAR_ELEVATION_SUNSET_SUNRISE = 0.0
 '''
-:float  The Sun's elevation at sunset and sunrise, measured in degrees
+:float  The Sun's elevation at sunset and sunrise,
+        measured in degrees
 '''
 
 SOLAR_ELEVATION_CIVIL_DUSK_DAWN = -6.0
 '''
-:float  The Sun's elevation at civil dusk and civil dawn, measured in degrees
+:float  The Sun's elevation at civil dusk and civil
+        dawn, measured in degrees
 '''
 
 SOLAR_ELEVATION_NAUTICAL_DUSK_DAWN = -12.0
 '''
-:float  The Sun's elevation at nautical dusk and nautical dawn, measured in degrees
+:float  The Sun's elevation at nautical dusk and
+        nautical dawn, measured in degrees
 '''
 
 SOLAR_ELEVATION_ASTRONOMICAL_DUSK_DAWN = -18.0
 '''
-:float  The Sun's elevation at astronomical dusk and astronomical dawn, measured in degrees
+:float  The Sun's elevation at astronomical dusk
+        and astronomical dawn, measured in degrees
 '''
 
 SOLAR_ELEVATION_RANGE_TWILIGHT = (-18.0, 0.0)
 '''
-:(float, float)  The Sun's lowest and highest elevation during all periods of twilight, measured in degrees
+:(float, float)  The Sun's lowest and highest elevation during
+                 all periods of twilight, measured in degrees
 '''
 
 SOLAR_ELEVATION_RANGE_CIVIL_TWILIGHT = (-6.0, 0.0)
 '''
-:(float, float)  The Sun's lowest and highest elevation during civil twilight, measured in degrees
+:(float, float)  The Sun's lowest and highest elevation
+                 during civil twilight, measured in degrees
 '''
 
 SOLAR_ELEVATION_RANGE_NAUTICAL_TWILIGHT = (-12.0, -6.0)
 '''
-:(float, float)  The Sun's lowest and highest elevation during nautical twilight, measured in degrees
+:(float, float)  The Sun's lowest and highest elevation
+                 during nautical twilight, measured in degrees
 '''
 
 SOLAR_ELEVATION_RANGE_ASTRONOMICAL_TWILIGHT = (-18.0, -12.0)
 '''
-:(float, float)  The Sun's lowest and highest elevation during astronomical twilight, measured in degrees
+:(float, float)  The Sun's lowest and highest elevation during
+                 astronomical twilight, measured in degrees
 '''
 
 
@@ -73,7 +81,7 @@ def sun(latitude, longitude, t = None, low = -6.0, high = 3.0):
     @param   low:float        The 100 % night limit elevation of the Sun (highest when not visible)
     @param   high:float       The 100 % day limit elevation of the Sun (lowest while fully visible)
     @return  :float           The visibilty of the Sun, 0 during the night, 1 during the day,
-                              between 0 and 1 during twilight. Other values will not occur.
+                              between 0 and 1 during twilight. Other values will not occur
     '''
     t = julian_centuries() if t is None else t
     e = solar_elevation(latitude, longitude, t)
@@ -85,7 +93,7 @@ def sun(latitude, longitude, t = None, low = -6.0, high = 3.0):
 # The following functions are used to calculate the result for `sun`
 # (most of them) but could be used for anything else. There name is
 # should tell you enough, `t` (and `noon`) is in Julian centuries
-# except for in the convertion methods
+# except for in the convertion methods.
 
 
 def julian_day_to_epoch(t):
@@ -279,7 +287,8 @@ def sun_apparent_longitude(t):
 
 def mean_ecliptic_obliquity(t):
     '''
-    Calculates the mean ecliptic obliquity of the Sun's apparent motion without variation correction
+    Calculates the mean ecliptic obliquity of the Sun's
+    apparent motion without variation correction
     
     @param   t:float  The time in Julian Centuries
     @return  :float   The uncorrected mean obliquity, in radians
@@ -292,7 +301,8 @@ def mean_ecliptic_obliquity(t):
 
 def corrected_mean_ecliptic_obliquity(t):
     '''
-    Calculates the mean ecliptic obliquity of the Sun's apparent motion with variation correction
+    Calculates the mean ecliptic obliquity of the Sun's
+    apparent motion with variation correction
     
     @param   t:float  The time in Julian Centuries
     @return  :float   The mean obliquity, in radians
@@ -317,7 +327,8 @@ def solar_declination(t):
 
 def equation_of_time(t):
     '''
-    Calculates the equation of time, the discrepancy between apparent and mean solar time
+    Calculates the equation of time, the discrepancy
+    between apparent and mean solar time
     
     @param   t:float  The time in Julian Centuries
     @return  :float   The equation of time, in degrees
@@ -338,7 +349,8 @@ def hour_angle_from_elevation(latitude, declination, elevation):
     '''
     Calculates the solar hour angle from the Sun's elevation
     
-    @param   longitude:float    The longitude in degrees eastwards from Greenwich, negative for westwards
+    @param   longitude:float    The longitude in degrees eastwards
+                                from Greenwich, negative for westwards
     @param   declination:float  The declination, in degrees
     @param   hour_angle:float   The Sun's elevation, in degrees
     @return  :float             The solar hour angle, in degrees
@@ -356,7 +368,8 @@ def elevation_from_hour_angle(latitude, declination, hour_angle):
     '''
     Calculates the Sun's elevation from the solar hour angle
     
-    @param   longitude:float    The longitude in degrees eastwards from Greenwich, negative for westwards
+    @param   longitude:float    The longitude in degrees eastwards
+                                from Greenwich, negative for westwards
     @param   declination:float  The declination, in degrees
     @param   hour_angle:float   The solar hour angle, in degrees
     @return  :float             The Sun's elevation, in degrees
@@ -372,7 +385,8 @@ def time_of_solar_noon(t, longitude):
     Calculates the time of the closest solar noon
     
     @param   t:float          A time close to the seeked time, in Julian Centuries
-    @param   longitude:float  The longitude in degrees eastwards from Greenwich, negative for westwards
+    @param   longitude:float  The longitude in degrees eastwards from
+                              Greenwich, negative for westwards
     @return  :float           The time, in Julian Centuries, of the closest solar noon
     '''
     t, rc = julian_centuries_to_julian_day(t), longitude
@@ -384,12 +398,15 @@ def time_of_solar_noon(t, longitude):
 
 def time_of_solar_elevation(t, noon, latitude, longitude, elevation):
     '''
-    Calculates the time the Sun has a specified apparent elevation at a geographical position
+    Calculates the time the Sun has a specified apparent
+    elevation at a geographical position
     
     @param   t:float          A time close to the seeked time, in Julian Centuries
     @param   noon:float       The time of the closest solar noon
-    @param   latitude:float   The latitude in degrees northwards from the equator, negative for southwards
-    @param   longitude:float  The longitude in degrees eastwards from Greenwich, negative for westwards
+    @param   latitude:float   The latitude in degrees northwards from
+                              the equator, negative for southwards
+    @param   longitude:float  The longitude in degrees eastwards from
+                              Greenwich, negative for westwards
     @param   elevation:float  The solar elevation, in degrees
     @return  :float           The time, in Julian Centuries, of the specified elevation
     '''
@@ -407,12 +424,16 @@ def time_of_solar_elevation(t, noon, latitude, longitude, elevation):
 
 def solar_elevation_from_time(t, latitude, longitude):
     '''
-    Calculates the Sun's elevation as apparent from a geographical position
+    Calculates the Sun's elevation as apparent
+    from a geographical position
     
     @param   t:float          The time in Julian Centuries
-    @param   latitude:float   The latitude in degrees northwards from the equator, negative for southwards
-    @param   longitude:float  The longitude in degrees eastwards from Greenwich, negative for westwards
-    @return  :float           The Sun's apparent at the specified time as seen from the specified position,
+    @param   latitude:float   The latitude in degrees northwards from
+                              the equator, negative for southwards
+    @param   longitude:float  The longitude in degrees eastwards from
+                              Greenwich, negative for westwards
+    @return  :float           The Sun's apparent at the specified time
+                              as seen from the specified position,
                               measured in degrees
     '''
     rc = julian_centuries_to_julian_day(t)
@@ -424,12 +445,17 @@ def solar_elevation_from_time(t, latitude, longitude):
 
 def solar_elevation(latitude, longitude, t = None):
     '''
-    Calculates the Sun's elevation as apparent from a geographical position
-    
-    @param   latitude:float   The latitude in degrees northwards from the equator, negative for southwards
-    @param   longitude:float  The longitude in degrees eastwards from Greenwich, negative for westwards
-    @param   t:float?         The time in Julian Centuries, `None` for the current time
-    @return  :float           The Sun's apparent at the specified time as seen from the specified position,
+    Calculates the Sun's elevation as apparent
+    from a geographical position
+    
+    @param   latitude:float   The latitude in degrees northwards from
+                              the equator, negative for southwards
+    @param   longitude:float  The longitude in degrees eastwards from
+                              Greenwich, negative for westwards
+    @param   t:float?         The time in Julian Centuries, `None`
+                              for the current time
+    @return  :float           The Sun's apparent at the specified time
+                              as seen from the specified position,
                               measured in degrees
     '''
     rc = julian_centuries() if t is None else t
@@ -441,12 +467,16 @@ def solar_elevation(latitude, longitude, t = None):
 # TODO document
 def have_sunrise_and_sunset(latitude, t = None):
     '''
-    Determine whether solar declination currently is so that there can be sunrises and sunsets.
-    If not, you either have 24-hour daytime or 24-hour nighttime.
+    Determine whether solar declination currently is
+    so that there can be sunrises and sunsets. If not,
+    you either have 24-hour daytime or 24-hour nighttime.
     
-    @param   latitude:float  The latitude in degrees northwards from the equator, negative for southwards
-    @param   t:float?        The time in Julian Centuries, `None` for the current time
-    @return                  Whether there can be sunrises and sunsets where you are located
+    @param   latitude:float  The latitude in degrees northwards from
+                             the equator, negative for southwards
+    @param   t:float?        The time in Julian Centuries, `None`
+                             for the current time
+    @return                  Whether there can be sunrises and
+                             sunsets where you are located
     '''
     t = julian_centuries() if t is None else t
     d = degrees(solar_declination(t))
@@ -465,9 +495,12 @@ def is_summer(latitude, t = None):
     '''
     Determine whether it is summer
     
-    @param   latitude:float  The latitude in degrees northwards from the equator, negative for southwards
-    @param   t:float?        The time in Julian Centuries, `None` for the current time
-    @return                  Whether it is summer on the hemisphere you are located on
+    @param   latitude:float  The latitude in degrees northwards from
+                             the equator, negative for southwards
+    @param   t:float?        The time in Julian Centuries, `None`
+                             for the current time
+    @return                  Whether it is summer on the hemisphere
+                             you are located on
     '''
     t = julian_centuries() if t is None else t
     d = solar_declination(t)
@@ -479,9 +512,12 @@ def is_winter(latitude, t = None):
     '''
     Determine whether it is winter
     
-    @param   latitude:float  The latitude in degrees northwards from the equator, negative for southwards
-    @param   t:float?        The time in Julian Centuries, `None` for the current time
-    @return                  Whether it is winter on the hemisphere you are located on
+    @param   latitude:float  The latitude in degrees northwards from
+                             the equator, negative for southwards
+    @param   t:float?        The time in Julian Centuries, `None`
+                             for the current time
+    @return                  Whether it is winter on the hemisphere
+                             you are located on
     '''
     t = julian_centuries() if t is None else t
     d = solar_declination(t)
@@ -492,15 +528,21 @@ def is_winter(latitude, t = None):
 # TODO document
 def solar_prediction(delta, requested, fun, epsilon = 0.000001, span = 0.01, t = None):
     '''
-    Predict the time point of the next or previous time an arbitrary condition is meet
+    Predict the time point of the next or previous
+    time an arbitrary condition is meet
     
-    @param   delta:float          Iteration step size, negative for past event, positive for future event
-    @param   requested:float      The value returned by `fun` for which to calculate the time point of occurrence
+    @param   delta:float          Iteration step size, negative for past
+                                  event, positive for future event
+    @param   requested:float      The value returned by `fun` for which to
+                                  calculate the time point of occurrence
     @param   fun:(t:float)→float  Function that calculate the data of interest
     @param   epsilon:float        Error tolerance for `requested`
-    @param   span:float           The number of Julian centuries (0,01 for one year) to restrict the search to
-    @param   t:float?             The time in Julian Centuries, `None` for the current time
-    @return  :float?              The calculated time point, `None` if none were found within the specified time span
+    @param   span:float           The number of Julian centuries (0,01 for
+                                  one year) to restrict the search to
+    @param   t:float?             The time in Julian Centuries, `None` for
+                                  the current time
+    @return  :float?              The calculated time point, `None` if none
+                                  were found within the specified time span
     '''
     t = julian_centuries() if t is None else t
     t1 = t2 = t
@@ -542,8 +584,10 @@ def future_past_equinox(delta, t = None):
     '''
     Predict the time point of the next or previous equinox
     
-    @param   delta:float  Iteration step size, negative for past event, positive for future event
-    @param   t:float?     The time in Julian Centuries, `None` for the current time
+    @param   delta:float  Iteration step size, negative for
+                          past event, positive for future event
+    @param   t:float?     The time in Julian Centuries, `None`
+                          for the current time
     @return  :float       The calculated time point
     '''
     return solar_prediction(delta, 0, solar_declination, t = t)
@@ -554,8 +598,10 @@ def future_equinox(t = None):
     '''
     Predict the time point of the next equinox
     
-    @param   delta:float  Iteration step size, negative for past event, positive for future event
-    @param   t:float?     The time in Julian Centuries, `None` for the current time
+    @param   delta:float  Iteration step size, negative for
+                          past event, positive for future event
+    @param   t:float?     The time in Julian Centuries, `None`
+                          for the current time
     @return  :float       The calculated time point
     '''
     return future_past_equinox(0.01 / 2000, t)
@@ -566,8 +612,10 @@ def past_equinox(t = None):
     '''
     Predict the time point of the previous equinox
     
-    @param   delta:float  Iteration step size, negative for past event, positive for future event
-    @param   t:float?     The time in Julian Centuries, `None` for the current time
+    @param   delta:float  Iteration step size, negative for
+                          past event, positive for future event
+    @param   t:float?     The time in Julian Centuries, `None`
+                          for the current time
     @return  :float       The calculated time point
     '''
     return future_past_equinox(0.01 / -2000, t)
@@ -579,13 +627,16 @@ def future_past_solstice(delta, t = None):
     '''
     Predict the time point of the next or previous solstice
     
-    @param   delta:float  Iteration step size, negative for past event, positive for future event
-    @param   t:float?     The time in Julian Centuries, `None` for the current time
+    @param   delta:float  Iteration step size, negative for
+                          past event, positive for future event
+    @param   t:float?     The time in Julian Centuries, `None`
+                          for the current time
     @return  :float       The calculated time point
     '''
     e = 0.00001
-    fun = lambda t : (solar_declination(t + e) - solar_declination(t - e)) / 2
-    return solar_prediction(delta, 0, fun, t = t)
+    fun = solar_declination
+    dfun = lambda t : (fun(t + e) - fun(t - e)) / 2
+    return solar_prediction(delta, 0, dfun, t = t)
 
 
 # TODO document
@@ -593,7 +644,8 @@ def future_solstice(t = None):
     '''
     Predict the time point of the next solstice
     
-    @param   t:float?  The time in Julian Centuries, `None` for the current time
+    @param   t:float?  The time in Julian Centuries,
+                       `None` for the current time
     @return  :float    The calculated time point
     '''
     return future_past_solstice(0.01 / 2000, t)
@@ -604,7 +656,8 @@ def past_solstice(t = None):
     '''
     Predict the time point of the previous solstice
     
-    @param   t:float?  The time in Julian Centuries, `None` for the current time
+    @param   t:float?  The time in Julian Centuries,
+                       `None` for the current time
     @return  :float    The calculated time point
     '''
     return future_past_solstice(0.01 / -2000, t)
@@ -613,111 +666,164 @@ def past_solstice(t = None):
 
 def future_past_elevation(delta, latitude, longitude, elevation, t = None):
     '''
-    Predict the time point of the next or previous time the Sun reaches or reached a specific elevation
+    Predict the time point of the next or previous time
+    the Sun reaches or reached a specific elevation
     
-    @param   delta:float      Iteration step size, negative for past event, positive for future event
-    @param   latitude:float   The latitude in degrees northwards from the equator, negative for southwards
-    @param   longitude:float  The longitude in degrees eastwards from Greenwich, negative for westwards
+    @param   delta:float      Iteration step size, negative for past
+                              event, positive for future event
+    @param   latitude:float   The latitude in degrees northwards from
+                              the equator, negative for southwards
+    @param   longitude:float  The longitude in degrees eastwards from
+                              Greenwich, negative for westwards
     @param   elevation:float  The elevation of interest
-    @param   t:float?         The time in Julian Centuries, `None` for the current time
-    @return  :float?          The calculated time point, `None` if none were found within a year
+    @param   t:float?         The time in Julian Centuries, `None`
+                              for the current time
+    @return  :float?          The calculated time point, `None` if
+                              none were found within a year
     '''
-    return solar_prediction(delta, elevation, lambda t : solar_elevation(latitude, longitude, t), t = t)
+    fun = lambda t : solar_elevation(latitude, longitude, t)
+    return solar_prediction(delta, elevation, fun, t = t)
 
 
 def future_elevation(latitude, longitude, elevation, t = None):
     '''
-    Predict the time point of the next time the Sun reaches a specific elevation
+    Predict the time point of the next time the Sun
+    reaches a specific elevation
     
-    @param   latitude:float   The latitude in degrees northwards from the equator, negative for southwards
-    @param   longitude:float  The longitude in degrees eastwards from Greenwich, negative for westwards
+    @param   latitude:float   The latitude in degrees northwards from
+                              the equator, negative for southwards
+    @param   longitude:float  The longitude in degrees eastwards from
+                              Greenwich, negative for westwards
     @param   elevation:float  The elevation of interest
-    @param   t:float?         The time in Julian Centuries, `None` for the current time
-    @return  :float?          The calculated time point, `None` if none were found within a year
+    @param   t:float?         The time in Julian Centuries, `None`
+                              for the current time
+    @return  :float?          The calculated time point, `None` if
+                              none were found within a year
     '''
     return future_past_elevation(0.01 / 2000, latitude, longitude, elevation, t)
     
 
 def past_elevation(latitude, longitude, elevation, t = None):
     '''
-    Predict the time point of the previous time the Sun reached a specific elevation
+    Predict the time point of the previous time the Sun
+    reached a specific elevation
     
-    @param   latitude:float   The latitude in degrees northwards from the equator, negative for southwards
-    @param   longitude:float  The longitude in degrees eastwards from Greenwich, negative for westwards
+    @param   latitude:float   The latitude in degrees northwards from
+                              the equator, negative for southwards
+    @param   longitude:float  The longitude in degrees eastwards from
+                              Greenwich, negative for westwards
     @param   elevation:float  The elevation of interest
-    @param   t:float?         The time in Julian Centuries, `None` for the current time
-    @return  :float?          The calculated time point, `None` if none were found within a year
+    @param   t:float?         The time in Julian Centuries, `None`
+                              for the current time
+    @return  :float?          The calculated time point, `None` if
+                              none were found within a year
     '''
     return future_past_elevation(0.01 / -2000, latitude, longitude, elevation, t)
 
 
 
 # TODO document
-def future_past_elevation_derivative(delta, latitude, longitude, elevation_derivative, t = None):
-    '''
-    Predict the time point of the next or previous time the Sun reaches or reached a specific elevation derivative
-    
-    @param   delta:float                 Iteration step size, negative for past event, positive for future event
-    @param   latitude:float              The latitude in degrees northwards from the equator, negative for southwards
-    @param   longitude:float             The longitude in degrees eastwards from Greenwich, negative for westwards
-    @param   elevation_derivative:float  The elevation derivative value of interest
-    @param   t:float?                    The time in Julian Centuries, `None` for the current time
-    @return  :float?                     The calculated time point, `None` if none were found within a year
+def future_past_elevation_derivative(delta, latitude, longitude, derivative, t = None):
+    '''
+    Predict the time point of the next or previous time the
+    Sun reaches or reached a specific elevation derivative
+    
+    @param   delta:float       Iteration step size, negative for past
+                               event, positive for future event
+    @param   latitude:float    The latitude in degrees northwards from
+                               the equator, negative for southwards
+    @param   longitude:float   The longitude in degrees eastwards from
+                               Greenwich, negative for westwards
+    @param   derivative:float  The elevation derivative value of interest
+    @param   t:float?          The time in Julian Centuries, `None`
+                               for the current time
+    @return  :float?           The calculated time point, `None` if
+                               none were found within a year
     '''
     fun = lambda t : solar_elevation(latitude, longitude, t)
     dfun = lambda t : (fun(t + e) - fun(t - e)) / 2
-    return solar_prediction(delta, elevation_derivative, dfun, t = t)
+    return solar_prediction(delta, derivative, dfun, t = t)
 
 
 # TODO document
-def future_elevation_derivative(latitude, longitude, elevation_derivative, t = None):
+def future_elevation_derivative(latitude, longitude, derivative, t = None):
     '''
-    Predict the time point of the next time the Sun reaches a specific elevation derivative
+    Predict the time point of the next time the
+    Sun reaches a specific elevation derivative
     
-    @param   latitude:float              The latitude in degrees northwards from the equator, negative for southwards
-    @param   longitude:float             The longitude in degrees eastwards from Greenwich, negative for westwards
-    @param   elevation_derivative:float  The elevation derivative value of interest
-    @param   t:float?                    The time in Julian Centuries, `None` for the current time
-    @return  :float?                     The calculated time point, `None` if none were found within a year
+    @param   latitude:float    The latitude in degrees northwards from
+                               the equator, negative for southwards
+    @param   longitude:float   The longitude in degrees eastwards from
+                               Greenwich, negative for westwards
+    @param   derivative:float  The elevation derivative value of interest
+    @param   t:float?          The time in Julian Centuries, `None`
+                               for the current time
+    @return  :float?           The calculated time point, `None` if
+                               none were found within a year
     '''
-    return future_past_elevation_derivative(0.01 / 2000, latitude, longitude, elevation_derivative, t)
+    return future_past_elevation_derivative(0.01 / 2000, latitude, longitude, derivative, t)
     
 
 # TODO document
-def past_elevation_derivative(latitude, longitude, elevation_derivative, t = None):
+def past_elevation_derivative(latitude, longitude, derivative, t = None):
     '''
-    Predict the time point of the previous time the Sun reached a specific elevation derivative
+    Predict the time point of the previous time
+    the Sun reached a specific elevation derivative
     
-    @param   latitude:float              The latitude in degrees northwards from the equator, negative for southwards
-    @param   longitude:float             The longitude in degrees eastwards from Greenwich, negative for westwards
-    @param   elevation_derivative:float  The elevation derivative value of interest
-    @param   t:float?                    The time in Julian Centuries, `None` for the current time
-    @return  :float?                     The calculated time point, `None` if none were found within a year
+    @param   latitude:float    The latitude in degrees northwards from
+                               the equator, negative for southwards
+    @param   longitude:float   The longitude in degrees eastwards from
+                               Greenwich, negative for westwards
+    @param   derivative:float  The elevation derivative value of interest
+    @param   t:float?          The time in Julian Centuries, `None`
+                               for the current time
+    @return  :float?           The calculated time point, `None`
+                               if none were found within a year
     '''
-    return future_past_elevation_derivative(0.01 / -2000, latitude, longitude, elevation_derivative, t)
+    return future_past_elevation_derivative(0.01 / -2000, latitude, longitude, derivative, t)
 
 
 
 # TODO: This algorithm is imprecise, gives an incorrent sunrise and I do not fully know its behaviour
 def sunrise_equation(latitude, longitude, t = None):
+    # Calculate Julian Cycle
     j_cent = julian_centuries() if t is None else t
     j_date = julian_centuries_to_julian_day(j_cent)
     j_cycle = int(j_date - 2451545.0009 - longitude / 360 + 0.5)
+    
+    # Calculate approximate solar noon and solar man anomaly
     approx_solar_noon = 451545.0009 + longitude / 360 + j_cycle
     solar_mean_anomaly = int(357.5291 + 0.98560028 * (j_cycle - 2451545)) % 360
-    equation_of_centre =  1.9148 * sin(1 * solar_mean_anomaly)
+    
+    # Calculate solar equation of centre
+    equation_of_centre  = 1.9148 * sin(1 * solar_mean_anomaly)
     equation_of_centre += 0.0200 * sin(2 * solar_mean_anomaly)
     equation_of_centre += 0.0003 * sin(3 * solar_mean_anomaly)
+    
+    # Calculate solar ecliptic longitude
     ecliptic_longitude = (solar_mean_anomaly + 102.9372 + equation_of_centre + 180) % 360
-    solar_transit = approx_solar_noon + 0.0053 * sin(solar_mean_anomaly) - 0.0069 * sin(2 * ecliptic_longitude)
+    
+    # Calculate solar transit
+    solar_transit  = approx_solar_noon + 0.0053 * sin(solar_mean_anomaly)
+    solar_transit -= 0.0069 * sin(2 * ecliptic_longitude)
+    
+    # Calculate solar declination
     declination = asin(sin(ecliptic_longitude) * sin(radians(23.45)))
-    hour_angle = sin(radians(-0.83))
+    
+    # Calculate solar hour angle
+    hour_angle  = sin(radians(-0.83))
     hour_angle -= sin(latitude) * sin(declination)
     hour_angle /= cos(latitude) * cos(declination)
     hour_angle = degrees(acos(hour_angle))
-    sunset = 2451545.0009 + (hour_angle + longitude) / 360 + j_cycle + solar_transit - approx_solar_noon
+    
+    # Calculate time of sunset and sunrise
+    sunset  = 2451545.0009 + (hour_angle + longitude) / 360
+    sunset += j_cycle + solar_transit - approx_solar_noon
     sunrise = 2 * solar_transit - sunset
-    return (julian_day_to_julian_centuries(sunset), julian_day_to_julian_centuries(sunrise))
+    
+    # Convert to Julian Centuries
+    return (julian_day_to_julian_centuries(sunset),
+            julian_day_to_julian_centuries(sunrise))