diff --git a/index.html b/index.html
index 8e13a94..246f721 100644
--- a/index.html
+++ b/index.html
@@ -56,6 +56,7 @@
     <script type="text/javascript" src="js/modules/pgm.js"></script>
     <script type="text/javascript" src="js/modules/fixedstars.js"></script>
     <script type="text/javascript" src="js/modules/fruitmachines.js"></script>
+    <script type="text/javascript" src="js/modules/psi.js"></script>
 
   </head>
 
@@ -341,7 +342,8 @@
           'hygromanteia_lunarsign',
           'kos_pday', 'kos_phour', 'kos_astro',
           'fruitmachine_day', 'fruitmachine_dignity',
-          'behenii'
+          'behenii',
+          'siderealpsi'
         ]);
 
         /*--
diff --git a/js/modules/psi.js b/js/modules/psi.js
new file mode 100644
index 0000000..f072d13
--- /dev/null
+++ b/js/modules/psi.js
@@ -0,0 +1,62 @@
+/**
+* @preserve Copyright (c) 2021 T. F. Raaion, www.sublunar.space
+* License MIT: http://www.opensource.org/licenses/MIT
+*/
+
+//Defines Calendar Objects and Methods
+  
+  var module_siderealpsi = {
+  
+    definitions: {
+      core: true,
+      name: "Sidereal Time Effect Size",
+      group: {
+        id: "siderealpsi",
+        text: "Psi"
+      },
+      actions: [
+        [0],
+        [
+          {
+            "id": "1",
+            "action": "Galactic Center Rising / Highest Effect Size (1997)",
+            "tags": "rising highest"
+          }
+        ],
+        [
+          {
+           "id": "2",
+           "action": "Highest Effect Size (2015)",
+           "tags": "highest"
+          }
+        ],
+        [
+          {
+            "id": "3",
+            "action": "Medium Effect Size",
+            "tags": "medium"
+          }
+        ],
+        [
+          {
+            "id": "4",
+            "action": "Galactic Center Overhead / Lowest Effect Size (1997)",
+            "tags": "overhead lowest"
+          }
+        ],
+      ]
+    },
+    property: function(m) {
+      return m.gst;
+    },
+    calculate: function(definitions, property) {
+      return definitions.actions[getEffectSize(property)];
+    }
+  };
+  
+  function getEffectSize(property) {
+    if ( property > 12.75 && property < 14.25 ) return 1;
+    if ( property > 17.4 && property < 20 ) return 4;
+    if ( property > 6 && property < 8 ) return 2;
+    else return 3;
+  }
\ No newline at end of file