diff --git a/ugali/observation/mask.py b/ugali/observation/mask.py
index <HASH>..<HASH> 100644
--- a/ugali/observation/mask.py
+++ b/ugali/observation/mask.py
@@ -223,7 +223,7 @@ class Mask:
         if method == 'step':
             func = lambda delta: (delta > 0).astype(float)
         elif method == 'erf':
-            # Trust the ERD???
+            # Trust the SDSS EDR???
             # 95% completeness: 
             def func(delta):
                 # Efficiency at bright end (assumed to be 100%)
@@ -232,6 +232,14 @@ class Mask:
                 width = 0.2 
                 # This should be the halfway point in the curve
                 return (e/2.0)*(1/np.sqrt(2*width))*(np.sqrt(2*width)-scipy.special.erf(-delta))
+        elif method = 'flemming':
+            # Functional form taken from Fleming et al. AJ 109, 1044 (1995)
+            # http://adsabs.harvard.edu/abs/1995AJ....109.1044F
+            # f = 1/2 [1 - alpha(V - Vlim)/sqrt(1 + alpha^2 (V - Vlim)^2)]
+            # CAREFUL: This definition is for Vlim = 50% completeness
+            def func(delta):
+                alpha = 2.0
+                return 0.5 * (1 - (alpha * delta)/np.sqrt(1+alpha**2 * delta**2))
         else:
             raise Exception('...')
         return func(delta)
Added Flemming completeness function