Index: /branches/eam_branches/ipp-20100621/psModules/src/objects/pmSourceMoments.c
===================================================================
--- /branches/eam_branches/ipp-20100621/psModules/src/objects/pmSourceMoments.c	(revision 28970)
+++ /branches/eam_branches/ipp-20100621/psModules/src/objects/pmSourceMoments.c	(revision 28971)
@@ -145,9 +145,11 @@
             psF32 wDiff = *vWgt;
 
-	    // skip pixels below specified significance level.  this is allowed, but should be
-	    // avoided -- the over-weights the wings of bright stars compared to those of faint
-	    // stars.
-            if (PS_SQR(pDiff) < minSN2*wDiff) continue;
-            // if (pDiff < 0) continue; // XXX : MWV says I should include < 0.0 valued points...
+	    // skip pixels below specified significance level.  for a PSFs, this
+	    // over-weights the wings of bright stars compared to those of faint stars.
+	    // for the estimator used for extended source analysis (where the window
+	    // function is allowed to be arbitrarily large), we need to clip to avoid
+	    // negative second moments.
+            if (PS_SQR(pDiff) < minSN2*wDiff) continue; // 
+            if ((minSN > 0.0) && (pDiff < 0)) continue; // 
 
 	    // Apply a Gaussian window function.  Be careful with the window function.  S/N