diff --git a/solpolpy/polarizers.py b/solpolpy/polarizers.py
index 001105e..b22191c 100644
--- a/solpolpy/polarizers.py
+++ b/solpolpy/polarizers.py
@@ -21,8 +21,10 @@ def npol_to_mzp(input_cube):
 
     if input_cube['angle_1'].meta['OBSRVTRY'] == 'STEREO_B':
         offset_angle = -18 * u.degree * conv_fact  # STEREOB
-    if input_cube['angle_1'].meta['OBSRVTRY'] == 'STEREO_A':
+    elif input_cube['angle_1'].meta['OBSRVTRY'] == 'STEREO_A':
         offset_angle = 45.8 * u.degree * conv_fact  # STEREOA
+    else:
+        offset_angle = 0
 
     for p_angle in in_list:
         if p_angle == "alpha":
@@ -33,7 +35,7 @@ def npol_to_mzp(input_cube):
     mzp_ang = [-60, 0, 60]
     Bmzp = {}
     for ang in mzp_ang: Bmzp[ang * u.degree] = (1 / 3) * np.sum(
-        [ith_polarizer_brightness * (1 + 2 * np.cos(2 * (ang * u.degree * conv_fact - (ith_angle-offset_angle))))
+        [ith_polarizer_brightness * (1 + 2 * np.cos(2 * (ang * u.degree * conv_fact - (ith_angle-offset_angle* u.degree * conv_fact))))
          for ith_angle, ith_polarizer_brightness in input_dict.items()], axis=0)
 
     # todo: update header properly; time info?