Index: /branches/czw_branch/20160809/psastro/src/psastroModelAdjust.c
===================================================================
--- /branches/czw_branch/20160809/psastro/src/psastroModelAdjust.c	(revision 39705)
+++ /branches/czw_branch/20160809/psastro/src/psastroModelAdjust.c	(revision 39706)
@@ -91,5 +91,6 @@
 
     // get the current posangle of the ref chip
-    float chipAngle = atan2 (refChip->toFPA->y->coeff[1][0], refChip->toFPA->x->coeff[1][0]);
+    // this should have a negative sign : chipAngle = -atan2 (dM/dy, dM/dx)
+    float chipAngle = -atan2 (refChip->toFPA->y->coeff[1][0], refChip->toFPA->x->coeff[1][0]);
 
     // chipAngle should be refChipAngleNominal @ POSANGLE = 0.0
@@ -110,4 +111,5 @@
 	psRegion *region = pmChipPixels (chip);
 
+	// this should ALSO have a negative sign: this rotates by +posAngleOffset
 	psPlaneTransform *toFPA = psPlaneTransformRotate (NULL, chip->toFPA, posAngleOffset);
 	psFree (chip->toFPA);