Index: trunk/ppStack/src/ppStackCombinePrepare.c
===================================================================
--- trunk/ppStack/src/ppStackCombinePrepare.c	(revision 30620)
+++ trunk/ppStack/src/ppStackCombinePrepare.c	(revision 34800)
@@ -1,5 +1,5 @@
 #include "ppStack.h"
 
-bool ppStackCombinePrepare(const char *outName, const char *expName,
+bool ppStackCombinePrepare(const char *outName, const char *expName, const char *bkgName,
                            ppStackFileList files, ppStackThreadData *stack,
                            ppStackOptions *options, pmConfig *config)
@@ -27,6 +27,46 @@
     options->outRO = pmReadoutAlloc(cell); // Output readout
 
-    pmCell *expCell = pmFPAfileThisCell(config->files, view, expName); // Exposure cell
-    options->expRO = pmReadoutAlloc(expCell); // Output readout
+    if (expName) {
+      pmCell *expCell = pmFPAfileThisCell(config->files, view, expName); // Exposure cell
+      options->expRO = pmReadoutAlloc(expCell); //Output readout
+    }
+/*     else { */
+/*       options->expRO = NULL; */
+/*     } */
+    pmCell *bkgCell;
+    int bkg_r0,bkg_c0;
+    int bkg_nC,bkg_nR;
+    if (bkgName) {
+      ppStackFileActivationSingle(config, PPSTACK_FILES_BKG, true, 0);
+      pmFPAfile *file = pmFPAfileSelectSingle(config->files, "PPSTACK.INPUT.BKGMODEL", 0);
+      pmFPAview *view = ppStackFilesIterateDown(config);
+      pmReadout *ro = pmFPAviewThisReadout(view,file->fpa);
+
+      bkg_r0 = ro->image->row0;
+      bkg_c0 = ro->image->col0;
+      bkg_nC = ro->image->numCols;
+      bkg_nR = ro->image->numRows;
+      bkgCell = pmFPAfileThisCell(config->files, view, bkgName); // Bkg cell
+      
+      options->bkgRO = pmReadoutAlloc(bkgCell); // BKG readout
+      //      if (!pmHDUGenerateForFPA(options->bkgRO->parent->parent->parent)) {
+      options->bkgRO->parent->parent->parent->hdu = pmHDUAlloc(NULL);
+      if (!options->bkgRO->parent->parent->parent->hdu) {
+	fprintf(stderr,"failed to generate a HDU for this thing.\n");
+      }
+      options->bkgRO->parent->parent->parent->hdu->header = psMetadataCopy(options->bkgRO->parent->parent->parent->hdu->header,
+									   ro->parent->parent->parent->hdu->header);
+
+      options->bkgRO->parent->concepts = psMetadataCopy(options->bkgRO->parent->concepts,
+							ro->parent->concepts);
+      options->bkgRO->parent->parent->concepts = psMetadataCopy(options->bkgRO->parent->parent->concepts,
+								ro->parent->parent->concepts);
+      options->bkgRO->parent->parent->parent->concepts = psMetadataCopy(options->bkgRO->parent->parent->parent->concepts,
+									ro->parent->parent->parent->concepts);
+
+    }
+    else {
+      options->bkgRO = NULL;
+    }
 
     psFree(view);
@@ -42,7 +82,19 @@
     }
 
-    if (!pmReadoutStackDefineOutput(options->expRO, col0, row0, numCols, numRows, true, true, 0)) {
+    if (expName) {
+      if (!pmReadoutStackDefineOutput(options->expRO, col0, row0, numCols, numRows, true, true, 0)) {
         psError(PPSTACK_ERR_ARGUMENTS, false, "Unable to prepare output.");
         return false;
+      }
+    }
+
+    if (bkgName) {
+      if (!pmReadoutStackDefineOutput(options->bkgRO, bkg_c0, bkg_r0, bkg_nC, bkg_nR, false, false, 0)) {
+        psError(PPSTACK_ERR_ARGUMENTS, false, "Unable to prepare output.");
+        return false;
+      }
+      
+
+      
     }