Index: trunk/psModules/src/detrend/pmOverscan.c
===================================================================
--- trunk/psModules/src/detrend/pmOverscan.c	(revision 23819)
+++ trunk/psModules/src/detrend/pmOverscan.c	(revision 23826)
@@ -255,4 +255,5 @@
     psMetadataAddStr(hdu->header, PS_LIST_TAIL, "HISTORY", PS_META_DUPLICATE_OK,
 		     comment, "");
+    psTrace ("psModules.detrend", 4, "%s\n", comment);
     psFree(comment);
 
@@ -344,4 +345,19 @@
 	}
 
+	// generate stats of overscan vector for header
+	{ 
+	  psString comment = NULL;    // Comment to add
+	  psStats *vectorStats = psStatsAlloc (PS_STAT_SAMPLE_MEAN | PS_STAT_SAMPLE_STDEV);
+	  psVectorStats (vectorStats, reduced, NULL, NULL, 0);
+	  psStringAppend(&comment, "Mean Overscan value: %f", vectorStats->sampleMean);
+	  psMetadataAddStr(hdu->header, PS_LIST_TAIL, "HISTORY", PS_META_DUPLICATE_OK, comment, "");
+	  psFree(comment);
+
+	  // write metadata header value
+	  psMetadataAddF32(hdu->header, PS_LIST_TAIL, "OVER_VAL", PS_META_REPLACE, "Overscan mean", vectorStats->sampleMean);
+	  psMetadataAddF32(hdu->header, PS_LIST_TAIL, "OVER_SIG", PS_META_REPLACE, "Overscan stdev", vectorStats->sampleStdev);
+	  psFree (vectorStats);
+	}
+
 	// Subtract row by row
 	for (int i = 0; i < image->numRows; i++) {
@@ -392,7 +408,22 @@
 	}
 
-	// Subtract column by column
-	for (int i = 0; i < image->numCols; i++) {
-	    for (int j = 0; j < image->numRows; j++) {
+	// generate stats of overscan vector for header
+	{ 
+	  psString comment = NULL;    // Comment to add
+	  psStats *vectorStats = psStatsAlloc (PS_STAT_SAMPLE_MEAN | PS_STAT_SAMPLE_STDEV);
+	  psVectorStats (vectorStats, reduced, NULL, NULL, 0);
+	  psStringAppend(&comment, "Mean Overscan value: %f", vectorStats->sampleMean);
+	  psMetadataAddStr(hdu->header, PS_LIST_TAIL, "HISTORY", PS_META_DUPLICATE_OK, comment, "");
+	  psFree(comment);
+
+	  // write metadata header value
+	  psMetadataAddF32(hdu->header, PS_LIST_TAIL, "OVER_VAL", PS_META_REPLACE, "Overscan mean", vectorStats->sampleMean);
+	  psMetadataAddF32(hdu->header, PS_LIST_TAIL, "OVER_SIG", PS_META_REPLACE, "Overscan stdev", vectorStats->sampleStdev);
+	  psFree (vectorStats);
+	}
+
+	// Subtract column by column 
+	for (int j = 0; j < image->numRows; j++) {
+	  for (int i = 0; i < image->numCols; i++) {
 		image->data.F32[j][i] -= reduced->data.F32[i];
 	    }