diff --git a/csaxs_bec/bec_ipython_client/plugins/omny/omny_rt.py b/csaxs_bec/bec_ipython_client/plugins/omny/omny_rt.py
index 901b0a12..f1b8c4af 100644
--- a/csaxs_bec/bec_ipython_client/plugins/omny/omny_rt.py
+++ b/csaxs_bec/bec_ipython_client/plugins/omny/omny_rt.py
@@ -22,9 +22,19 @@ class OMNY_rt_client:
     def __init__(self):
         self.mirror_channel = -1
         self.mirror_amplitutde_increase = 0
+        # Loaded lazily on first use so the OMNY session can start while rt is disabled/off.
         self.mirror_parameters = {}
-        for j in range(1, 9):
-            self.mirror_parameters[j] = dev.rtx.controller.get_mirror_parameters(j)
+
+    def _load_mirror_parameters(self):
+        if self.mirror_parameters:
+            return
+        if not dev.rtx.enabled:
+            raise OMNY_rt_clientError(
+                "Device rtx is disabled; cannot read interferometer mirror parameters."
+            )
+        self.mirror_parameters = {
+            j: dev.rtx.controller.get_mirror_parameters(j) for j in range(1, 9)
+        }
 
     @staticmethod
     def _get_user_param_safe(device, var):
@@ -42,6 +52,7 @@ class OMNY_rt_client:
         self._tweak_interferometer()
 
     def _tweak_interferometer(self):
+        self._load_mirror_parameters()
         self.mirror_channel = -1
 
         # Save the current terminal settings