diff --git a/kosmorrolib/data.py b/kosmorrolib/data.py
index e37cd0e..d7e931b 100644
--- a/kosmorrolib/data.py
+++ b/kosmorrolib/data.py
@@ -65,12 +65,17 @@ class Position:
         self.latitude = latitude
         self.longitude = longitude
         self.observation_planet = None
+        self._topos = None
 
     def get_planet_topos(self) -> Topos:
         if self.observation_planet is None:
             raise TypeError('Observation planet must be set.')
 
-        return self.observation_planet + Topos(latitude_degrees=self.latitude, longitude_degrees=self.longitude)
+        if self._topos is None:
+            self._topos = self.observation_planet + Topos(latitude_degrees=self.latitude,
+                                                          longitude_degrees=self.longitude)
+
+        return self._topos
 
 
 class AsterEphemerides: