diff --git a/star_chart_spherical_projection/declination_r_axis.py b/star_chart_spherical_projection/declination_r_axis.py
index 77fcc69..9bd75fc 100644
--- a/star_chart_spherical_projection/declination_r_axis.py
+++ b/star_chart_spherical_projection/declination_r_axis.py
@@ -28,7 +28,7 @@ def _calculate_radius_of_circle(min_dec, pole):
 def _calculate_ruler(declination_min, declination_max, increment, pole):
     # define the length of each segment in ruler when radius = 1
 
-    x_angleOfDeclination = np.arange(-90, 90+1,increment) # declination max range from -90 to 90
+    x_angle_of_declination = np.arange(-90, 90+1,increment) # declination max range from -90 to 90
     y_lengthSegments = []
 
     declination_angles_ruler = np.arange(-90, 90+1, increment) # declination max range from -90 to 90