Index: branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryDistortion.c
===================================================================
--- branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryDistortion.c	(revision 41821)
+++ branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryDistortion.c	(revision 41823)
@@ -340,12 +340,7 @@
     psRegion *region = pmAstromFPAExtent (fpa);
 
-    // XXX psFree (fpa->fromTPA);
-    // XXX psPlaneTransform *myPT = psPlaneTransformAlloc(fpa->toTPA->x->nX+4, fpa->toTPA->x->nY+4);
-    // XXX fpa->fromTPA = psPlaneTransformInvert(myPT, fpa->toTPA, *region, 50);
-    // XXX psFree (myPT);
-
     // as of r40806, psPlaneTransformInvert supplies the extra order (if non-linear)
     psFree (fpa->fromTPA);
-    fpa->fromTPA = psPlaneTransformInvert(NULL, fpa->toTPA, *region, 50, 4);
+    fpa->fromTPA = psPlaneTransformInvert(NULL, fpa->toTPA, *region, 50, EXTRA_ORDERS);
     psFree (region);
 
Index: branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryModel.c
===================================================================
--- branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryModel.c	(revision 41821)
+++ branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryModel.c	(revision 41823)
@@ -525,5 +525,5 @@
 	// as of r40806, psPlaneTransformInvert supplies the extra order (if non-linear)
         psFree (chip->fromFPA);
-        chip->fromFPA = psPlaneTransformInvert(NULL, chip->toFPA, *region, 50, 4);
+        chip->fromFPA = psPlaneTransformInvert(NULL, chip->toFPA, *region, 50, EXTRA_ORDERS);
 
         psFree (region);
@@ -585,12 +585,7 @@
     psRegion *region = pmAstromFPAExtent (file->fpa);
 
-    // XXX psFree (file->fpa->fromTPA);
-    // XXX psPlaneTransform *myPT = psPlaneTransformAlloc(file->fpa->toTPA->x->nX+4, file->fpa->toTPA->x->nY+4);
-    // XXX file->fpa->fromTPA = psPlaneTransformInvert(myPT, file->fpa->toTPA, *region, 50);
-    // XXX psFree (myPT);
-
     // as of r40806, psPlaneTransformInvert supplies the extra order (if non-linear)
     psFree (file->fpa->fromTPA);
-    file->fpa->fromTPA = psPlaneTransformInvert(NULL, file->fpa->toTPA, *region, 50, 4);
+    file->fpa->fromTPA = psPlaneTransformInvert(NULL, file->fpa->toTPA, *region, 50, EXTRA_ORDERS);
 
     psFree (model);
@@ -728,8 +723,4 @@
     psLogMsg ("psModules.astrom", 4, "Position Angle: %f, Model Position Angle Zero Point: %f\n", POS, PosZero);
 
-//    psPlaneTransform *fromTPA = psPlaneTransformRotate (NULL, file->fpa->fromTPA, rotatorParity * (PosZero - POS));
-//    psFree (file->fpa->fromTPA);
-//    file->fpa->fromTPA = fromTPA;
-
     psPlaneTransform *toTPA = psPlaneTransformRotate (NULL, file->fpa->toTPA, rotatorParity * (POS - PosZero));
     psFree (file->fpa->toTPA);
@@ -739,11 +730,6 @@
     psRegion *region = pmAstromFPAExtent (file->fpa);
 
-    // XXX psFree (file->fpa->fromTPA);
-    // XXX psPlaneTransform *myPT = psPlaneTransformAlloc(file->fpa->toTPA->x->nX+4, file->fpa->toTPA->x->nY+4);
-    // XXX file->fpa->fromTPA = psPlaneTransformInvert(myPT, file->fpa->toTPA, *region, 50);
-    // XXX psFree (myPT);
-
     psFree (file->fpa->fromTPA);
-    file->fpa->fromTPA = psPlaneTransformInvert(NULL, file->fpa->toTPA, *region, 50, 4);
+    file->fpa->fromTPA = psPlaneTransformInvert(NULL, file->fpa->toTPA, *region, 50, EXTRA_ORDERS);
 
     psFree (region);
Index: branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryRegions.h
===================================================================
--- branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryRegions.h	(revision 41821)
+++ branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryRegions.h	(revision 41823)
@@ -10,4 +10,7 @@
 #ifndef PM_ASTROMETRY_REGIONS_H
 #define PM_ASTROMETRY_REGIONS_H
+
+// used by pmAstrometryDistortion.c, pmAstrometryWCS.c, pmAstrometryModel.c
+# define EXTRA_ORDERS 6
 
 /// @addtogroup Astrometry
Index: branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryWCS.c
===================================================================
--- branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryWCS.c	(revision 41821)
+++ branches/eam_branches/ipp-dev-20210817/psModules/src/astrom/pmAstrometryWCS.c	(revision 41823)
@@ -608,5 +608,5 @@
     // as of r40806, psPlaneTransformInvert supplies the extra order (if non-linear)
     psFree (chip->fromFPA);
-    chip->fromFPA = psPlaneTransformInvert(NULL, chip->toFPA, *region, 50, 4);
+    chip->fromFPA = psPlaneTransformInvert(NULL, chip->toFPA, *region, 50, EXTRA_ORDERS);
     psFree (region);
 
@@ -668,5 +668,5 @@
     // as of r40806, psPlaneTransformInvert supplies the extra order (if non-linear)
     psFree (chip->fromFPA);
-    chip->fromFPA = psPlaneTransformInvert(NULL, chip->toFPA, *region, 50, 4);
+    chip->fromFPA = psPlaneTransformInvert(NULL, chip->toFPA, *region, 50, EXTRA_ORDERS);
     psFree (region);
 
@@ -700,5 +700,5 @@
     // the region defines the FPA pixels covered by the tranformation
     psFree (fpa->fromTPA);
-    int additional_orders = 4;  // This is the number of orders that should be added.
+    int additional_orders = EXTRA_ORDERS;  // This is the number of orders that should be added.
     bool status = false;
     int config_additional_orders = psMetadataLookupS32(&status,fpa->analysis, "ADDITIONAL_WCS_ORDERS");
@@ -1032,5 +1032,5 @@
 
     // NOTE: the extraOrders value (4) should be ignored since outToFPA is specified to be linear
-    psPlaneTransform *outFromFPA = psPlaneTransformInvert(NULL, outToFPA, *outputBounds, 50, 4);
+    psPlaneTransform *outFromFPA = psPlaneTransformInvert(NULL, outToFPA, *outputBounds, 50, EXTRA_ORDERS);
     if (!outFromFPA) {
         psFree(outToFPA);
@@ -1148,5 +1148,5 @@
     psFree(dst);
 
-    // this is a linear transformation
+    // this is a linear transformation, no extra orders are needed
     psPlaneTransform *newFromFPA = psPlaneTransformInvert(NULL, newToFPA, *bounds, 1, 0);
     if (!newFromFPA) {