Index: /trunk/Ohana/src/opihi/lib.data/starfuncs.c
===================================================================
--- /trunk/Ohana/src/opihi/lib.data/starfuncs.c	(revision 19825)
+++ /trunk/Ohana/src/opihi/lib.data/starfuncs.c	(revision 19826)
@@ -44,4 +44,6 @@
   dsky2 = dsky2 / Npts - sky*sky;
   free (ring);
+
+  float dx, dy;
 
   peak = 0;
@@ -52,9 +54,11 @@
       value = gfits_get_matrix_value (matrix, i, j);
       offset = value - sky;
-      x  += i*offset;
-      y  += j*offset;
-      x2 += i*i*offset;
-      y2 += j*j*offset;
-      xy += i*j*offset;
+      dx = i - X;
+      dy = j - Y;
+      x  += dx*offset;
+      y  += dy*offset;
+      x2 += dx*dx*offset;
+      y2 += dy*dy*offset;
+      xy += dx*dy*offset;
       I  += offset;
       Npts ++;