Index: trunk/psphot/src/psphotApResid.c
===================================================================
--- trunk/psphot/src/psphotApResid.c	(revision 34404)
+++ trunk/psphot/src/psphotApResid.c	(revision 36623)
@@ -214,5 +214,5 @@
 
         // XXX make this user-configurable?
-        if (source->psfMagErr > 0.01) continue;
+        if (source->psfMagErr > 0.03) continue;
 
         // aperture residual for this source
@@ -267,10 +267,11 @@
 
     // set the max order (0 = constant) which the number of psf stars can support:
-    // rule of thumb: require 3 stars per 'cell' (order+1)^2
+    // we require only 3 stars for n = 0, increase stars / cell for higher order
     int MaxOrderForStars = 0;
-    if (Npsf >= 12) MaxOrderForStars = 1; // 4 cells
-    if (Npsf >= 27) MaxOrderForStars = 2; // 9 cells
-    if (Npsf >= 48) MaxOrderForStars = 3; // 16 cells
-    if (Npsf >  75) MaxOrderForStars = 4; // 25 cells
+    if (Npsf >=  16) MaxOrderForStars = 1; // 4 cells
+    if (Npsf >=  54) MaxOrderForStars = 2; // 9 cells
+    if (Npsf >= 128) MaxOrderForStars = 3; // 16 cells
+    if (Npsf >= 300) MaxOrderForStars = 4; // 25 cells
+    if (Npsf >  576) MaxOrderForStars = 5; // 36 cells
 
     pmTrend2DMode mode = PM_TREND_MAP;