diff --git a/ImageD11/sinograms/dataset.py b/ImageD11/sinograms/dataset.py
index 1ec1497e..67f55644 100644
--- a/ImageD11/sinograms/dataset.py
+++ b/ImageD11/sinograms/dataset.py
@@ -102,21 +102,19 @@ def guess_detector(self):
         
         # open the masterfile
         hname = self.masterfile
+        detectors_seen = []
+        scan = "1.1"
+
         with h5py.File( hname, 'r' ) as hin:
-            detectors_seen = []
             # go through the first scan, and see what detectors we can see
-            scan = "1.1"
-            # scans = [scan for scan in list(hin['/']) if (scan.endswith('.1') and ('measurement' in hin[scan]))]
-            # for scan in scans:
             for measurement in list(hin[scan]['measurement']):
                 if measurement in POSSIBLE_DETECTOR_NAMES:
                     detectors_seen.append(measurement)
-                    
-        unique_detectors_seen = list(set(detectors_seen))
-        if len(unique_detectors_seen) != 1:
+        
+        if len(detectors_seen) != 1:
             raise ValueError("More than one detector seen! Can't work out which one to process.")
         else:
-            self.detector = unique_detectors_seen[0]
+            self.detector = detectors_seen[0]
             
         
     def guess_motornames(self):
@@ -124,25 +122,23 @@ def guess_motornames(self):
         from ImageD11.sinograms.assemble_label import HEADERMOTORS_NSCOPE, HEADERMOTORS_TDXRD, HEADERMOTORS
         # open the masterfile
         hname = self.masterfile
+        motors_seen = []
+        scan = "1.1"
+        
         with h5py.File( hname, 'r' ) as hin:
-            motors_seen = []
-            # go through all the scans, and see what motors we can see
-            # scans = [scan for scan in list(hin['/']) if (scan.endswith('.1') and ('measurement' in hin[scan]))]
-            scan = "1.1"
-            # for scan in scans:
+            # go through the first scan, and see what motors we can see
             for positioner in list(hin[scan]['instrument/positioners']):
                 if positioner in HEADERMOTORS:
                     motors_seen.append(positioner)
-                        
-        unique_motors_seen = list(set(motors_seen))
+        
         using_nscope = False
         using_tdxrd = False
-        for unique_motor in unique_motors_seen:
-            if unique_motor in HEADERMOTORS_NSCOPE:
+        for motor in motors_seen:
+            if motor in HEADERMOTORS_NSCOPE:
                 using_nscope = True
-            elif unique_motor in HEADERMOTORS_TDXRD:
+            elif motor in HEADERMOTORS_TDXRD:
                 using_tdxrd = True
-                
+        
         if using_nscope and using_tdxrd:
             raise ValueError("Found both nscope and tdxrd motors in positioners, not sure which one we were using!")