diff --git a/bdsf/functions.py b/bdsf/functions.py
index b33dfd27..2ce3a627 100644
--- a/bdsf/functions.py
+++ b/bdsf/functions.py
@@ -45,28 +45,13 @@ def shapeletfit(cf, Bset, cfshape):
     return y
 
 
-def atanproper(dumr, dx, dy):
-    from math import pi
-
-    ysign = (dy >= 0.0)
-    xsign = (dx >= 0.0)
-    if ysign and (not xsign): dumr = pi - dumr
-    if (not ysign) and (not xsign): dumr = pi + dumr
-    if (not ysign) and xsign: dumr = 2.0*pi - dumr
-
-    return dumr
-
 def gdist_pa(pix1, pix2, gsize):
     """ Computes FWHM in degrees in the direction towards second source, of an elliptical gaussian. """
-    from math import atan, pi, sqrt, cos, sin, tan
+    from math import atan, atan2, pi, sqrt, cos, sin, tan
 
     dx = pix2[0] - pix1[0]
     dy = pix2[1] - pix1[1]
-    if dx == 0.0:
-        val = pi/2.0
-    else:
-        dumr = atan(abs(dy/dx))
-        val = atanproper(dumr, dx, dy)
+    val = atan2(dy, dx)
 
     psi = val - (gsize[2]+90.0)/180.0*pi
 
@@ -422,8 +407,7 @@ def momanalmask_gaus(subim, mask, isrc, bmar_p, allpara=True):
 
         mompara[3] = sqrt((m2[0]+m2[1]+sqrt((m2[0]-m2[1])*(m2[0]-m2[1])+4.0*m11*m11))/(2.0*tot))*fwsig
         mompara[4] = sqrt((m2[0]+m2[1]-sqrt((m2[0]-m2[1])*(m2[0]-m2[1])+4.0*m11*m11))/(2.0*tot))*fwsig
-        dumr = atan(abs(2.0*m11/(m2[0]-m2[1])))
-        dumr = atanproper(dumr, m2[0]-m2[1], 2.0*m11)
+        dumr = N.arctan2(2.0*m11, m2[0]-m2[1]) % (2.0*pi)
         mompara[5] = 0.5*dumr*180.0/pi - 90.0
         if mompara[5] < 0.0: mompara[5] += 180.0
     return mompara