Index: trunk/ppStack/src/ppStackLoop.c
===================================================================
--- trunk/ppStack/src/ppStackLoop.c	(revision 31435)
+++ trunk/ppStack/src/ppStackLoop.c	(revision 34800)
@@ -63,5 +63,5 @@
 
     // Prepare for combination
-    if (!ppStackCombinePrepare("PPSTACK.OUTPUT", "PPSTACK.OUTPUT.EXP", PPSTACK_FILES_STACK, stack, options, config)) {
+    if (!ppStackCombinePrepare("PPSTACK.OUTPUT", "PPSTACK.OUTPUT.EXP", "PPSTACK.OUTPUT.BKGMODEL", PPSTACK_FILES_STACK, stack, options, config)) {
         psError(psErrorCodeLast(), false, "Unable to prepare for combination.");
         psFree(stack);
@@ -84,5 +84,5 @@
         pmCellFreeData(options->cells->data[i]);
     }
-    psFree(stack);
+    //    psFree(stack);
 
     // Pixel rejection
@@ -142,4 +142,11 @@
     }
 
+    // Generate median background stack here.
+    if (!ppStackCombineBackground(stack, options, config)) {
+      psError(psErrorCodeLast(), false, "Unable to generate median of background images.");
+      psFree(stack);
+      return false;
+    }
+    ppStackFileActivation(config,PPSTACK_FILES_BKG ,false);    
     // Photometry
     psTrace("ppStack", 1, "Photometering stacked image....\n");
@@ -171,5 +178,5 @@
         return false;
     }
-    psFree(stack);
+    //    psFree(stack);
     psLogMsg("ppStack", PS_LOG_INFO, "Stage 7: Cleanup, WCS & JPEGS: %f sec", psTimerClear("PPSTACK_STEPS"));
     ppStackMemDump("cleanup");
@@ -186,5 +193,5 @@
 
         // Prepare for combination
-        if (!ppStackCombinePrepare("PPSTACK.UNCONV", "PPSTACK.UNCONV.EXP", PPSTACK_FILES_UNCONV,
+        if (!ppStackCombinePrepare("PPSTACK.UNCONV", "PPSTACK.UNCONV.EXP", NULL, PPSTACK_FILES_UNCONV,
                                    stack, options, config)) {
             psError(psErrorCodeLast(), false, "Unable to prepare for combination.");