diff --git a/spectrum.py b/spectrum.py
index e765508..7c2d3b2 100755
--- a/spectrum.py
+++ b/spectrum.py
@@ -578,7 +578,9 @@ bias = {
     ),
 }
 
-mean_bias = np.mean( [ bias[ 'top' ] , bias[ 'down' ] ] , axis = 0 )
+print( bias[ 'top' ] , bias[ 'down' ] )
+mean_bias = np.mean( [ bias[ 'top' ] , bias[ 'down' ] ] , axis = 0 ) / 2
+print( 'mean_bias spectrum: ' + str( mean_bias ) )
 
 if verbose:
     print( 'bias substraction finished' )