diff --git a/observation_sim/ObservationSim.py b/observation_sim/ObservationSim.py
index 4fa42d4d75e99e1930daa92333fbac37692769d5..cb060ab4d65520e8a3ae76b5b5f678a88cfe43d0 100755
--- a/observation_sim/ObservationSim.py
+++ b/observation_sim/ObservationSim.py
@@ -23,7 +23,7 @@ class Observation(object):
         self.filter_param = FilterParam()
         self.Catalog = Catalog
 
-    def prepare_chip_for_exposure(self, chip, ra_cen, dec_cen, pointing, wcs_fp=None, slsPSFOptim = False):
+    def prepare_chip_for_exposure(self, chip, ra_cen, dec_cen, pointing, wcs_fp=None, slsPSFOptim=False):
         # Get WCS for the focal plane
         if wcs_fp == None:
             wcs_fp = self.focal_plane.getTanWCS(
@@ -35,21 +35,22 @@ class Observation(object):
         chip.img.wcs = wcs_fp
 
         chip.slsPSFOptim = slsPSFOptim
-        if chip.chipID in [1,2,3,4,5,10,21,26,27,28,29,30] and slsPSFOptim:
+        if chip.chipID in [1, 2, 3, 4, 5, 10, 21, 26, 27, 28, 29, 30] and slsPSFOptim:
             chip.img_stack = {}
             for id1 in np.arange(2):
                 gn = chip_utils.getChipSLSGratingID(chip.chipID)[id1]
                 orders = {}
                 # for id2 in ['-2','-1','0','1','2']:
-                for id2 in ['0','1']:
+                for id2 in ['0', '1']:
                     o_n = "order"+id2
                     allbands = {}
-                    for id3 in ['1','2','3','4']:
+                    for id3 in ['1', '2', '3', '4']:
                         w_n = "w"+id3
                         allbands[w_n] = galsim.ImageF(chip.npix_x, chip.npix_y)
-                        allbands[w_n].setOrigin(chip.bound.xmin, chip.bound.ymin)
+                        allbands[w_n].setOrigin(
+                            chip.bound.xmin, chip.bound.ymin)
                         allbands[w_n].wcs = wcs_fp
-                    orders[o_n] = allbands      
+                    orders[o_n] = allbands
                 chip.img_stack[gn] = orders
         else:
             chip.img_stack = {}
@@ -111,16 +112,17 @@ class Observation(object):
                 input_date_str=date_str,
                 input_time_str=time_str
             )
-            ra_cen, dec_cen = ra_cen[0], dec_cen[0]
-            ra_offset, dec_offset = pointing.ra - ra_cen, pointing.dec - dec_cen
+            ra_offset, dec_offset = pointing.ra - \
+                ra_cen[0], pointing.dec - dec_cen[0]
         else:
-            ra_cen = pointing.ra
-            dec_cen = pointing.dec
             ra_offset, dec_offset = 0., 0.
-            
+        ra_cen = pointing.ra
+        dec_cen = pointing.dec
+
         slsPSFOpt = False
         # Prepare necessary chip properties for simulation
-        chip = self.prepare_chip_for_exposure(chip, ra_cen, dec_cen, pointing, slsPSFOptim = slsPSFOpt)
+        chip = self.prepare_chip_for_exposure(
+            chip, ra_cen, dec_cen, pointing, slsPSFOptim=slsPSFOpt)
 
         # Initialize SimSteps
         sim_steps = SimSteps(overall_config=self.config,
diff --git a/observation_sim/config/ChipOutput.py b/observation_sim/config/ChipOutput.py
index 5efd0616e8870d90a0844279d476d4817a9a2135..7db5e12d465534523c040a7e1d9e66330ece659e 100755
--- a/observation_sim/config/ChipOutput.py
+++ b/observation_sim/config/ChipOutput.py
@@ -78,12 +78,12 @@ class ChipOutput(object):
                 self.hdr += "\n"
             self.cat.write(self.hdr)
 
-    def cat_add_obj(self, obj, pos_img, pos_shear):
+    def cat_add_obj(self, obj, pos_img, pos_shear, ra_offset=0., dec_offset=0.):
         ximg = obj.real_pos.x + 1.0
         yimg = obj.real_pos.y + 1.0
 
         line = self.fmt % (
-            obj.id, int(self.chip_label), self.filt.filter_type, ximg, yimg, obj.ra, obj.dec, obj.ra_orig, obj.dec_orig, obj.z, obj.getMagFilter(
+            obj.id, int(self.chip_label), self.filt.filter_type, ximg, yimg, obj.ra + ra_offset, obj.dec + dec_offset, obj.ra_orig, obj.dec_orig, obj.z, obj.getMagFilter(
                 self.filt), obj.type,
             obj.pmra, obj.pmdec, obj.rv, obj.parallax)
         line += obj.additional_output_str
diff --git a/observation_sim/sim_steps/add_objects.py b/observation_sim/sim_steps/add_objects.py
index 9ce6c0acd9604a901b2e2b72ec96865da3dc0a6f..6c9c7c197577b2c8a3fda456043366b03d40691e 100644
--- a/observation_sim/sim_steps/add_objects.py
+++ b/observation_sim/sim_steps/add_objects.py
@@ -194,7 +194,8 @@ def add_objects(self, chip, filt, tel, pointing, catalog, obs_param):
 
             if isUpdated == 1:
                 # TODO: add up stats
-                self.chip_output.cat_add_obj(obj, pos_img, pos_shear)
+                self.chip_output.cat_add_obj(
+                    obj, pos_img, pos_shear, ra_offset=self.ra_offset, dec_offset=self.dec_offset)
                 pass
             elif isUpdated == 0:
                 missed_obj += 1
@@ -236,7 +237,7 @@ def add_objects(self, chip, filt, tel, pointing, catalog, obs_param):
         # fits.writeto('order0.fits',img1[0],overwrite=True)
         # fits.writeto('order1.fits',img1[1],overwrite=True)
 
-        psf_model.convolveFullImgWithPCAPSF(chip) 
+        psf_model.convolveFullImgWithPCAPSF(chip)
     del psf_model
     gc.collect()