DOC: Update gallery example for Figure.solar (#3858)

Author: yvonnefroehlich

examples/gallery/embellishments/solar.py

@@ -1,12 +1,12 @@
 """
-Day-night terminator line and twilights
-=======================================
+Day-night terminator and twilights
+==================================
 
-Use :meth:`pygmt.Figure.solar` to show the different transition stages between
-daytime and nighttime. The parameter ``terminator`` is used to set the twilight
-stage, and can be either ``"day_night"`` (brightest), ``"civil"``,
-``"nautical"``, or ``"astronomical"`` (darkest).
-Refer to https://en.wikipedia.org/wiki/Twilight for more information.
+Use :meth:`pygmt.Figure.solar` to show the different transition stages between daytime
+and nighttime. The parameter ``terminator`` is used to set the twilight stage, and can
+be either ``"day_night"`` (brightest), ``"civil"``, ``"nautical"``, or
+``"astronomical"`` (darkest). Refer to https://en.wikipedia.org/wiki/Twilight for more
+information.
 """
 
 # %%
@@ -15,39 +15,24 @@
 import pygmt
 
 fig = pygmt.Figure()
-# Create a figure showing the global region on a Mollweide projection
-# Land color is set to dark green and water color is set to light blue
-fig.coast(region="d", projection="W0/15c", land="darkgreen", water="lightblue")
-# Set a time for the day-night terminator and twilights, 17:00 UTC on
-# January 1, 2000
-terminator_datetime = datetime.datetime(
+# Create a global map using the Mollweide projection, centered at 0°E, with a width of
+# 15 centimeters.
+fig.basemap(region="d", projection="W15c", frame=True)
+fig.coast(land="darkgreen", water="lightblue")
+
+# Set a time for the day-night terminator and twilights to 17:00 UTC on January 1, 2000
+reference_time = datetime.datetime(
     year=2000, month=1, day=1, hour=17, minute=0, second=0
 )
-# Set the pen line to be 0.5 points thick
-# Set the fill for the night area to be navy blue at different transparency
-# levels
-fig.solar(
-    terminator="day_night",
-    terminator_datetime=terminator_datetime,
-    fill="navyblue@95",
-    pen="0.5p",
-)
-fig.solar(
-    terminator="civil",
-    terminator_datetime=terminator_datetime,
-    fill="navyblue@85",
-    pen="0.5p",
-)
-fig.solar(
-    terminator="nautical",
-    terminator_datetime=terminator_datetime,
-    fill="navyblue@80",
-    pen="0.5p",
-)
-fig.solar(
-    terminator="astronomical",
-    terminator_datetime=terminator_datetime,
-    fill="navyblue@80",
-    pen="0.5p",
-)
+
+# Plot the day-night terminator and twilights
+for terminator in ["day_night", "civil", "nautical", "astronomical"]:
+    fig.solar(
+        terminator=terminator,
+        terminator_datetime=reference_time,
+        # Set the fill for the night area to navy blue with 85 % transparency
+        fill="navyblue@85",
+        pen="0.5p",  # Set the outline to be 0.5 points thick
+    )
+
 fig.show()