diff --git a/tupak/gw/detector.py b/tupak/gw/detector.py
index ac17539cfc87326ca607eedf14733c0da776b951..c2e7273bd89818e90c52d1e61d151cefa6a7ba69 100644
--- a/tupak/gw/detector.py
+++ b/tupak/gw/detector.py
@@ -292,9 +292,9 @@ class Interferometer(object):
         n - unit vector along arm in cartesian Earth-based coordinates
         """
         if arm == 'x':
-            return self.__calculate_arm(self.xarm_tilt, self.xarm_azimuth)
+            return self.__calculate_arm(self.__xarm_tilt, self.__xarm_azimuth)
         elif arm == 'y':
-            return self.__calculate_arm(self.yarm_tilt, self.yarm_azimuth)
+            return self.__calculate_arm(self.__yarm_tilt, self.__yarm_azimuth)
         else:
             logging.warning('Not a recognized arm, aborting!')
             return
diff --git a/tupak/gw/detectors/H1.interferometer b/tupak/gw/detectors/H1.interferometer
index 7289cf0b900622e46d1f7f0b94101e7317083caa..b524b929da26978e6731c2c9308db058e7312b9a 100644
--- a/tupak/gw/detectors/H1.interferometer
+++ b/tupak/gw/detectors/H1.interferometer
@@ -10,6 +10,6 @@ latitude = 46 + 27. / 60 + 18.528 / 3600
 longitude = -(119 + 24. / 60 + 27.5657 / 3600)
 elevation = 142.554
 xarm_azimuth = 125.9994
-yarm_azimuth = 215.994
+yarm_azimuth = 215.9994
 xarm_tilt = -6.195e-4
 yarm_tilt = 1.25e-5