add solar elevation derivative prediction

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

1 files changed, 15 insertions, 1 deletions

diff --git a/src/solar.py b/src/solar.py
index ef74c08..d3c19f5 100644
--- a/src/solar.py
+++ b/src/solar.py
@@ -516,7 +516,7 @@ def past_equinox(t = None):
 # TODO document
 def future_past_solstice(delta, t = None):
     e = 0.00001
-    fun = lambda t : (solar_declination(t - e) - solar_declination(t + e)) / 2
+    fun = lambda t : (solar_declination(t + e) - solar_declination(t - e)) / 2
     return solar_prediction(delta, 0, fun, t = t)
 
 
@@ -570,6 +570,20 @@ def past_elevation(latitude, longitude, elevation, t = None):
     return future_past_elevation(0.01 / -2000, latitude, longitude, elevation, t)
 
 
+def future_past_elevation_derivative(delta, latitude, longitude, elevation_derivative, t = None):
+    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)
+
+
+def future_elevation_derivative(latitude, longitude, elevation_derivative, t = None):
+    return future_past_elevation_derivative(0.01 / 2000, latitude, longitude, elevation_derivative, t)
+    
+
+def past_elevation_derivative(latitude, longitude, elevation_derivative, t = None):
+    return future_past_elevation_derivative(0.01 / -2000, latitude, longitude, elevation_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):
     j_cent = julian_centuries() if t is None else t