Fixed #131 - Added phase_fraction in C, C#.

The C and C# Illumination functions now return
a `phase_fraction` result to complement `phase_angle`.
This makes them consistent with the Python and JavaScript
versions.

generate/template/astronomy.c

@@ -466,6 +466,7 @@ static astro_illum_t IllumError(astro_status_t status)
     result.time = TimeError();
     result.mag = NAN;
     result.phase_angle = NAN;
+    result.phase_fraction = NAN;
     result.helio_dist = NAN;
     result.ring_tilt = NAN;
 
@@ -5364,6 +5365,7 @@ astro_illum_t Astronomy_Illumination(astro_body_t body, astro_time_t time)
     illum.time = time;
     illum.mag = mag;
     illum.phase_angle = phase.angle;
+    illum.phase_fraction = (1.0 + cos(DEG2RAD * phase.angle)) / 2.0;
     illum.helio_dist = helio_dist;
     illum.ring_tilt = ring_tilt;
 

generate/template/astronomy.cs

@@ -1358,6 +1358,9 @@ namespace CosineKitty
         /// <summary>The angle in degrees between the Sun and the Earth, as seen from the body. Indicates the body's phase as seen from the Earth.</summary>
         public readonly double phase_angle;
 
+        /// <summary>A value in the range [0.0, 1.0] indicating what fraction of the body's apparent disc is illuminated, as seen from the Earth.</summary>
+        public readonly double phase_fraction;
+
         /// <summary>The distance between the Sun and the body at the observation time.</summary>
         public readonly double helio_dist;
 
@@ -1369,6 +1372,7 @@ namespace CosineKitty
             this.time = time;
             this.mag = mag;
             this.phase_angle = phase_angle;
+            this.phase_fraction = (1.0 + Math.Cos(Astronomy.DEG2RAD * phase_angle)) / 2.0;
             this.helio_dist = helio_dist;
             this.ring_tilt = ring_tilt;
         }

source/c/README.md

@@ -3252,6 +3252,7 @@ Returned by the functions [`Astronomy_Illumination`](#Astronomy_Illumination) an
 | [`astro_time_t`](#astro_time_t) | `time` |  The date and time of the observation.  |
 | `double` | `mag` |  The visual magnitude of the body. Smaller values are brighter.  |
 | `double` | `phase_angle` |  The angle in degrees between the Sun and the Earth, as seen from the body. Indicates the body's phase as seen from the Earth.  |
+| `double` | `phase_fraction` |  A value in the range [0.0, 1.0] indicating what fraction of the body's apparent disc is illuminated, as seen from the Earth.  |
 | `double` | `helio_dist` |  The distance between the Sun and the body at the observation time.  |
 | `double` | `ring_tilt` |  For Saturn, the tilt angle in degrees of its rings as seen from Earth. For all other bodies, 0.  |
 

source/c/astronomy.c

@@ -466,6 +466,7 @@ static astro_illum_t IllumError(astro_status_t status)
     result.time = TimeError();
     result.mag = NAN;
     result.phase_angle = NAN;
+    result.phase_fraction = NAN;
     result.helio_dist = NAN;
     result.ring_tilt = NAN;
 
@@ -6590,6 +6591,7 @@ astro_illum_t Astronomy_Illumination(astro_body_t body, astro_time_t time)
     illum.time = time;
     illum.mag = mag;
     illum.phase_angle = phase.angle;
+    illum.phase_fraction = (1.0 + cos(DEG2RAD * phase.angle)) / 2.0;
     illum.helio_dist = helio_dist;
     illum.ring_tilt = ring_tilt;
 

source/c/astronomy.h

@@ -573,6 +573,7 @@ typedef struct
     astro_time_t        time;           /**< The date and time of the observation. */
     double              mag;            /**< The visual magnitude of the body. Smaller values are brighter. */
     double              phase_angle;    /**< The angle in degrees between the Sun and the Earth, as seen from the body. Indicates the body's phase as seen from the Earth. */
+    double              phase_fraction; /**< A value in the range [0.0, 1.0] indicating what fraction of the body's apparent disc is illuminated, as seen from the Earth. */
     double              helio_dist;     /**< The distance between the Sun and the body at the observation time. */
     double              ring_tilt;      /**< For Saturn, the tilt angle in degrees of its rings as seen from Earth. For all other bodies, 0. */
 }

source/csharp/README.md

@@ -2181,6 +2181,7 @@ to report the visual magnitude and illuminated fraction of a celestial body at a
 | [`AstroTime`](#AstroTime) | `time` | The date and time of the observation. |
 | `double` | `mag` | The visual magnitude of the body. Smaller values are brighter. |
 | `double` | `phase_angle` | The angle in degrees between the Sun and the Earth, as seen from the body. Indicates the body's phase as seen from the Earth. |
+| `double` | `phase_fraction` | A value in the range [0.0, 1.0] indicating what fraction of the body's apparent disc is illuminated, as seen from the Earth. |
 | `double` | `helio_dist` | The distance between the Sun and the body at the observation time. |
 | `double` | `ring_tilt` | For Saturn, the tilt angle in degrees of its rings as seen from Earth. For all other bodies, 0. |
 

source/csharp/astronomy.cs

@@ -1358,6 +1358,9 @@ namespace CosineKitty
         /// <summary>The angle in degrees between the Sun and the Earth, as seen from the body. Indicates the body's phase as seen from the Earth.</summary>
         public readonly double phase_angle;
 
+        /// <summary>A value in the range [0.0, 1.0] indicating what fraction of the body's apparent disc is illuminated, as seen from the Earth.</summary>
+        public readonly double phase_fraction;
+
         /// <summary>The distance between the Sun and the body at the observation time.</summary>
         public readonly double helio_dist;
 
@@ -1369,6 +1372,7 @@ namespace CosineKitty
             this.time = time;
             this.mag = mag;
             this.phase_angle = phase_angle;
+            this.phase_fraction = (1.0 + Math.Cos(Astronomy.DEG2RAD * phase_angle)) / 2.0;
             this.helio_dist = helio_dist;
             this.ring_tilt = ring_tilt;
         }