diff --git a/ObservationSim/MockObject/Galaxy.py b/ObservationSim/MockObject/Galaxy.py
index 315255fc427dcf1c3368647a311bc75be3b2fc3f..8fc86a563a2b3f38a83d06562491ab5985281591 100755
--- a/ObservationSim/MockObject/Galaxy.py
+++ b/ObservationSim/MockObject/Galaxy.py
@@ -310,7 +310,7 @@ class Galaxy(MockObject):
 
             origin_star = [y_nominal - (starImg.center.y - starImg.ymin),
                            x_nominal - (starImg.center.x - starImg.xmin)]
-
+            origin_star.setOrigin(0, 0)
             gal_origin = [origin_star[0], origin_star[1]]
             gal_end = [origin_star[0] + starImg.array.shape[0] - 1, origin_star[1] + starImg.array.shape[1] - 1]
 
@@ -320,6 +320,7 @@ class Galaxy(MockObject):
 
                 subImg_p1 = starImg.array[:, 0:subSlitPos]
                 star_p1 = galsim.Image(subImg_p1)
+                star_p1.setOrigin(0, 0)
                 origin_p1 = origin_star
                 xcenter_p1 = min(x_nominal,grating_split_pos_chip-1) - 0
                 ycenter_p1 = y_nominal-0
@@ -336,6 +337,7 @@ class Galaxy(MockObject):
 
                 subImg_p2 = starImg.array[:, subSlitPos+1:starImg.array.shape[1]]
                 star_p2 = galsim.Image(subImg_p2)
+                star_p2.setOrigin(0, 0)
                 origin_p2 = [origin_star[0], grating_split_pos_chip]
                 xcenter_p2 = max(x_nominal, grating_split_pos_chip - 1) - 0
                 ycenter_p2 = y_nominal - 0
diff --git a/ObservationSim/MockObject/MockObject.py b/ObservationSim/MockObject/MockObject.py
index ab8b234f998e179e2bd756fcadd4467845509272..ae29851024b17be7b264bf815f4a9f72ae449773 100755
--- a/ObservationSim/MockObject/MockObject.py
+++ b/ObservationSim/MockObject/MockObject.py
@@ -358,7 +358,7 @@ class MockObject(object):
 
             origin_star = [y_nominal - (starImg.center.y - starImg.ymin),
                            x_nominal - (starImg.center.x - starImg.xmin)]
-
+            origin_star.setOrigin(0,0)
             gal_origin = [origin_star[0], origin_star[1]]
             gal_end = [origin_star[0] + starImg.array.shape[0] - 1, origin_star[1] + starImg.array.shape[1] - 1]
 
@@ -369,6 +369,7 @@ class MockObject(object):
                 subImg_p1 = starImg.array[:, 0:subSlitPos]
                 star_p1 = galsim.Image(subImg_p1)
                 origin_p1 = origin_star
+                origin_p1.setOrigin(0,0)
                 xcenter_p1 = min(x_nominal, grating_split_pos_chip - 1) - 0
                 ycenter_p1 = y_nominal - 0
 
@@ -384,6 +385,7 @@ class MockObject(object):
 
                 subImg_p2 = starImg.array[:, subSlitPos + 1:starImg.array.shape[1]]
                 star_p2 = galsim.Image(subImg_p2)
+                star_p2.setOrigin(0, 0)
                 origin_p2 = [origin_star[0], grating_split_pos_chip]
                 xcenter_p2 = max(x_nominal, grating_split_pos_chip - 1) - 0
                 ycenter_p2 = y_nominal - 0