diff --git a/SAS/TMSS/backend/src/tmss/tmssapp/serializers/specification.py b/SAS/TMSS/backend/src/tmss/tmssapp/serializers/specification.py
index f24068cd0ce5bb6d6e6b6f08d435458e72d3c043..fad6357960023cfb2f09008259ac03027c8dcb06 100644
--- a/SAS/TMSS/backend/src/tmss/tmssapp/serializers/specification.py
+++ b/SAS/TMSS/backend/src/tmss/tmssapp/serializers/specification.py
@@ -347,7 +347,6 @@ class SchedulingUnitBlueprintPublicSerializer(serializers.ModelSerializer):
                             'status',
                             'on_sky_start_time',
                             'on_sky_stop_time',
-                            'on_sky_duration',
                             'target_pointings_astropy',
                             'project']
         fields = read_only_fields