Index: /branches/eam_rel9_b0/psModules/src/objects/pmPSFtry.c
===================================================================
--- /branches/eam_rel9_b0/psModules/src/objects/pmPSFtry.c	(revision 5810)
+++ /branches/eam_rel9_b0/psModules/src/objects/pmPSFtry.c	(revision 5811)
@@ -196,4 +196,5 @@
     stats->clipIter = 3;
 
+    // fit ApResid only to rflux, ignore x,y variations for now
     // linear clipped fit of ApResid to rflux
     psPolynomial1D *poly = psPolynomial1DAlloc (1, PS_POLYNOMIAL_ORD);
@@ -202,5 +203,5 @@
 
     psfTry->psf->ApTrend->coeff[0][0][0] = poly->coeff[0];
-    psfTry->psf->ApTrend->coeff[0][0][1] = poly->coeff[1];
+    psfTry->psf->ApTrend->coeff[0][0][1] = 0;
 
     psfTry->psf->skyBias  = poly->coeff[1] / (M_PI * PS_SQR(RADIUS));
@@ -214,2 +215,9 @@
     return true;
 }
+
+/*
+  (aprMag' - fitMag) = rflux*skyBias + ApTrend(x,y)
+  (aprMag - rflux*skyBias) - fitMag = ApTrend(x,y)
+  (aprMag - rflux*skyBias) = fitMag + ApTrend(x,y)
+*/
+