diff --git a/snsim/astrobj.py b/snsim/astrobj.py
index 87190ca..9ecaa0b 100644
--- a/snsim/astrobj.py
+++ b/snsim/astrobj.py
@@ -302,6 +302,27 @@ def _set_model_par(self, model):
             
             model.set_source_peakmag(self._sim_par['mb'], 'bessellb', 'ab')
             self._sim_par['x0'] = model.get('x0')
+            
+        elif self._relation.lower() == 'salttrip_BS20':
+            # TODO : COMPLETE BS20 using dev_damiano
+            self._obj_attrs.extend(['alpha', 'beta', 'RV', 'Edust', 'x0', 'x1', 'c'])
+            self._sim_par['mb'] = self.SALTTripp(
+                M0, 
+                self._sim_par['alpha'], 
+                self._sim_par['beta'], 
+                self._sim_par['RV'],
+                self._sim_par['Edust']
+                self._sim_par['x1'], 
+                self._sim_par['c']) + self.mu
+            
+            # Compute the x0 parameter
+            model.set(
+                x1=self._sim_par['x1'], 
+                c=self._sim_par['c'])
+            
+            model.set_source_peakmag(self._sim_par['mb'], 'bessellb', 'ab')
+            self._sim_par['x0'] = model.get('x0')
+            
         else:
             # TODO - BC : Find a way to use lambda function for relation
             raise ValueError('Relation not available')
@@ -309,8 +330,11 @@ def _set_model_par(self, model):
     
     @staticmethod
     def SALTTripp(M0, alpha, beta, x1, c):
-        return M0  + alpha * x1 - beta * c
+        return M0 - alpha * x1 + beta * c
 
+    @staticmethod
+    def SALTTrippBS20(M0, alpha, beta, RV, Edust, x1, c):
+        return M0 - alpha * x1 + beta * c + (RV + 1) * Edust
 
 class TimeSeries(AstrObj):
     """TimeSeries class.
diff --git a/snsim/tests/test_astrobj.py b/snsim/tests/test_astrobj.py
index a74e030..c21e39c 100644
--- a/snsim/tests/test_astrobj.py
+++ b/snsim/tests/test_astrobj.py
@@ -51,8 +51,8 @@ def setup_class(self):
     
     def test_tripp(self):
         mb = self.SNIa_Tripp.sim_par['M0'] + self.SNIa_Tripp.mu
-        mb += self.SNIa_Tripp.sim_par['alpha'] * self.SNIa_Tripp.sim_par['x1']
-        mb += -self.SNIa_Tripp.sim_par['beta'] * self.SNIa_Tripp.sim_par['c']
+        mb -= self.SNIa_Tripp.sim_par['alpha'] * self.SNIa_Tripp.sim_par['x1']
+        mb += self.SNIa_Tripp.sim_par['beta'] * self.SNIa_Tripp.sim_par['c']
         assert(self.SNIa_Tripp.mb == mb)
     
     def test_genflux(self):
diff --git a/snsim/tests/test_geout.py b/snsim/tests/test_geout.py
index ae88de6..d60330b 100644
--- a/snsim/tests/test_geout.py
+++ b/snsim/tests/test_geout.py
@@ -12,15 +12,5 @@ def test_compute_area():
     area = geo_ut._compute_area(polygon)
     assert_almost_equal(area, 4 * np.pi)
     
-    
-def test_compute_polygon():
-    
-    # Regular polygon
-    corners = np.array([[[np.pi - 0.02, 0.02]], [[np.pi + 0.02, 0.02]] ,
-                        [[np.pi + 0.02, -0.02]], [[np.pi - 0.02, -0.02]]])
-    
-    polygon = geo_ut._compute_polygon(corners)
-    
-    ra = np.random.uniform(0, 2 * np.pi, 10
-    
+
     
\ No newline at end of file