Merge pull request #1410 from Cadair/map_rotate_doc

Add a section to the guide about map alignment with plotting.

doc/source/guide/data_types/maps.rst

@@ -128,6 +128,15 @@ matplotlib figure object by using the plot() command.
 This makes it possible to use the SunPy plot as the foundation for a 
 more complicated figure.
 
+.. note::
+
+   If the `wcsaxes <http://wcsaxes.readthedocs.org/en/latest/>`_ package is not 
+   installed the `~sunpy.map.GenericMap.plot()` and `~sunpy.map.GenericMap.peek()`
+   methods assume that the data is not rotated,
+   i.e. the solar y axis is oriented with the columns of the array. If this condition
+   is not met, when the map is plotted a warning will be issued. You can create
+   an oriented map by using `~sunpy.map.GenericMap.rotate()` before you plot the Map.
+
 6. Overlaying Maps
 ------------------
 The `Map()` method described above can also handle a list of maps. If a list in inputs