Index: trunk/ppSub/src/ppSubReadoutInverse.c
===================================================================
--- trunk/ppSub/src/ppSubReadoutInverse.c	(revision 24240)
+++ trunk/ppSub/src/ppSubReadoutInverse.c	(revision 24255)
@@ -23,10 +23,12 @@
     invRO->data_exists = invRO->parent->data_exists = invRO->parent->parent->data_exists = true;
 
+    // Get concepts from reference
+    pmFPAfile *refFile = psMetadataLookupPtr(NULL, config->files, "PPSUB.REF.CONV"); // File with concepts
+    pmFPA *invFPA = invRO->parent->parent->parent; // Inverse FPA
+    pmConceptsCopyFPA(invFPA, refFile->fpa, true, true);
+
+    // Get astrometry from (forward) subtraction
     pmChip *outChip = outRO->parent->parent;       // Output chip
     pmFPA *outFPA = outChip->parent;               // Output FPA
-    pmFPA *invFPA = invRO->parent->parent->parent; // Inverse FPA
-
-    pmConceptsCopyFPA(invFPA, outFPA, true, true);
-
     pmChip *invChip = invRO->parent->parent; // Inverse chip
     pmHDU *invHDU = invFPA->hdu;          // Inverse HDU