Python: added documentation for function Illumination.

source/python/README.md

@@ -633,6 +633,36 @@ for more details.
 
 ---
 
+<a name="Illumination"></a>
+### Illumination(body, time)
+
+**Finds visual magnitude, phase angle, and other illumination information about a celestial body.**
+
+This function calculates information about how bright a celestial body appears from the Earth,
+reported as visual magnitude, which is a smaller (or even negative) number for brighter objects,
+and a larger number for dimmer objects.
+For bodies other than the Sun, it reports a phase angle, which is the angle in degrees between
+the Sun and the Earth, as seen from the center of the body. Phase angle indicates what fraction
+of the body appears illuminated as seen from the Earth. For example, when the phase angle is
+near zero, it means the body appears "full" as seen from the Earth.  A phase angle approaching
+180 degrees means the body appears as a thin crescent as seen from the Earth.  A phase angle
+of 90 degrees means the body appears "half full".
+For the Sun, the phase angle is always reported as 0; the Sun emits light rather than reflecting it,
+so it doesn't have a phase angle.
+When the body is Saturn, the returned object contains a field `ring_tilt` that holds
+the tilt angle in degrees of Saturn's rings as seen from the Earth. A value of 0 means
+the rings appear edge-on, and are thus nearly invisible from the Earth. The `ring_tilt` holds
+0 for all bodies other than Saturn.
+
+| Type | Parameter | Description |
+| --- | --- | --- |
+| [`Body`](#Body) | `body` | The Sun, Moon, or any planet other than the Earth. |
+| [`Time`](#Time) | `time` | The date and time of the observation. |
+
+### Returns: #IlluminationInfo
+
+---
+
 <a name="LongitudeFromSun"></a>
 ### LongitudeFromSun(body, time)
 

source/python/astronomy.py

@@ -4259,6 +4259,37 @@ def _VisualMagnitude(body, phase, helio_dist, geo_dist):
     return mag
 
 def Illumination(body, time):
+    """Finds visual magnitude, phase angle, and other illumination information about a celestial body.
+
+    This function calculates information about how bright a celestial body appears from the Earth,
+    reported as visual magnitude, which is a smaller (or even negative) number for brighter objects,
+    and a larger number for dimmer objects.
+
+    For bodies other than the Sun, it reports a phase angle, which is the angle in degrees between
+    the Sun and the Earth, as seen from the center of the body. Phase angle indicates what fraction
+    of the body appears illuminated as seen from the Earth. For example, when the phase angle is
+    near zero, it means the body appears "full" as seen from the Earth.  A phase angle approaching
+    180 degrees means the body appears as a thin crescent as seen from the Earth.  A phase angle
+    of 90 degrees means the body appears "half full".
+    For the Sun, the phase angle is always reported as 0; the Sun emits light rather than reflecting it,
+    so it doesn't have a phase angle.
+
+    When the body is Saturn, the returned object contains a field `ring_tilt` that holds
+    the tilt angle in degrees of Saturn's rings as seen from the Earth. A value of 0 means
+    the rings appear edge-on, and are thus nearly invisible from the Earth. The `ring_tilt` holds
+    0 for all bodies other than Saturn.
+
+    Parameters
+    ----------
+    body : Body
+        The Sun, Moon, or any planet other than the Earth.
+    time : Time
+        The date and time of the observation.
+
+    Returns
+    -------
+    #IlluminationInfo
+    """
     if body == Body.Earth:
         raise EarthNotAllowedError()
     earth = _CalcEarth(time)