diff --git a/python/damask/orientation.py b/python/damask/orientation.py
index a1fe1f845..1bc850734 100644
--- a/python/damask/orientation.py
+++ b/python/damask/orientation.py
@@ -574,6 +574,21 @@ class Symmetry:
 
     proper considers only vectors with z >= 0, hence uses two neighboring SSTs.
     Return inverse pole figure color if requested.
+    Bases are computed from
+
+    basis = {'cubic' :        np.linalg.inv(np.array([[0.,0.,1.],                                   # direction of red
+                                                      [1.,0.,1.]/np.sqrt(2.),                       # direction of green
+                                                      [1.,1.,1.]/np.sqrt(3.)]).T),                  # direction of blue
+             'hexagonal' :    np.linalg.inv(np.array([[0.,0.,1.],                                   # direction of red
+                                                      [1.,0.,0.],                                   # direction of green
+                                                      [np.sqrt(3.),1.,0.]/np.sqrt(4.)]).T),         # direction of blue
+             'tetragonal' :   np.linalg.inv(np.array([[0.,0.,1.],                                   # direction of red
+                                                      [1.,0.,0.],                                   # direction of green
+                                                      [1.,1.,0.]/np.sqrt(2.)]).T),                  # direction of blue
+             'orthorhombic' : np.linalg.inv(np.array([[0.,0.,1.],                                   # direction of red
+                                                      [1.,0.,0.],                                   # direction of green
+                                                      [0.,1.,0.]]).T),                              # direction of blue
+            }
     """
     if self.lattice == 'cubic':
       basis = {'improper':np.array([ [-1.            ,  0.            ,  1. ],