Index: /trunk/psastro/src/psastroMosaicAstrom.c
===================================================================
--- /trunk/psastro/src/psastroMosaicAstrom.c	(revision 15245)
+++ /trunk/psastro/src/psastroMosaicAstrom.c	(revision 15246)
@@ -80,4 +80,26 @@
     if (psTraceGetLevel("psastro.dump") > 0) { psastroDumpMatches (fpa, "match.5.dat"); }
 
+    // do a third pass on the distortion with improved chip positions and rotations
+    // first, re-perform the match with a slightly tighter circle
+    if (!psastroMosaicSetMatch (fpa, recipe, 2)) {
+	psError(PSASTRO_ERR_UNKNOWN, false, "failed to match raw and ref stars for mosaic (3rd pass)");
+	return false;
+    }
+    if (!psastroMosaicCommonScale (fpa, recipe)) {
+	psError(PSASTRO_ERR_UNKNOWN, false, "failed to set a common scale for the chips (3rd pass)");
+	return false;
+    }
+    if (!psastroMosaicGradients (fpa, recipe)) {
+	psError(PSASTRO_ERR_UNKNOWN, false, "failed to measure mosaic gradients (3rd pass)");
+	return false;
+    }
+    if (psTraceGetLevel("psastro.dump") > 0) { psastroDumpMatches (fpa, "match.6.dat"); }
+
+    if (!psastroMosaicChipAstrom (fpa, recipe, 0)) {
+	psError(PSASTRO_ERR_UNKNOWN, false, "failed to measure chip astrometry in mosaic mode (3rd pass)");
+	return false;
+    }
+    if (psTraceGetLevel("psastro.dump") > 0) { psastroDumpMatches (fpa, "match.7.dat"); }
+
     // now fit the chips under the common distortion with higher-order terms
     // first, re-perform the match with a slightly tighter circle
@@ -90,5 +112,5 @@
 	return false;
     }
-    if (psTraceGetLevel("psastro.dump") > 0) { psastroDumpMatches (fpa, "match.6.dat"); }
+    if (psTraceGetLevel("psastro.dump") > 0) { psastroDumpMatches (fpa, "match.8.dat"); }
 
     // save WCS and analysis metadata in update header.