Index: trunk/ppSim/src/ppSimInsertStars.c
===================================================================
--- trunk/ppSim/src/ppSimInsertStars.c	(revision 32350)
+++ trunk/ppSim/src/ppSimInsertStars.c	(revision 34083)
@@ -6,5 +6,5 @@
     PTR = NULL;
 
-float imageSum (psImage *image);
+double imageSum (psImage *image);
 
 bool ppSimInsertStars (pmReadout *readout, psImage *expCorr, psArray *stars, pmConfig *config) {
@@ -79,4 +79,6 @@
     FILE *outfile = fopen (outname, "w");
 
+    float radius = -1.0;
+
     // add sources to the readout image & variance
     psTrace("ppSim", 1, "Inserting %ld stars...\n", stars->n);
@@ -110,7 +112,11 @@
 	pmModelSetFlux (model, flux);
 
-	float radius = model->modelRadius (model->params, nSigmaLim * roughNoise);
-	radius = PS_MAX (radius, 1.0);
-	radius = 20.0;
+	// we must set the radius on the first object, and leave it there for everyone else
+	// (inserting flux with a variable radius introduces a flux-dependent bias)
+	if (radius < 0) {
+	  radius = model->modelRadius (model->params, nSigmaLim * roughNoise);
+	  radius = PS_MAX (radius,  1.0);
+	  radius = PS_MIN (radius, 50.0);
+	}
 
 	// construct a source, with model flux pixels set, based on the model
@@ -136,8 +142,10 @@
 	    readout->image->data.F32[(int)(yCell)][(int)(xCell)] += flux;
 	} else {
-	    // insert the source flux in the image
-	    float sum1 = imageSum(source->pixels);
+	    // insert the source flux in the image and measure inserted flux
+	    // this is a difference of 2 large numbers : must use 'double' or we get floating
+	    // point errors and trends on a scale of ~0.005 mags at > -10 mags instrumental
+	    double sum1 = imageSum(source->pixels);
 	    pmSourceAddWithOffset (source, PM_MODEL_OP_FULL, 0xff, dX, dY);
-	    float sum2 = imageSum(source->pixels);
+	    double sum2 = imageSum(source->pixels);
 	    starFlux = sum2 - sum1;
 	    
@@ -154,5 +162,5 @@
 	    RESET(source->blends);
 	}
-	fprintf (outfile, "%8.3f %8.3f %10.2f  %2d  %7.3f %5.3f  %5.3f %5.3f %5.3f %5.3f  :  %f %f\n", star->x, star->y, starFlux, 0, source->psfMag, source->psfMagErr, axes.major, axes.minor, axes.theta, par8, model->params->data.F32[PM_PAR_I0], radius);
+	fprintf (outfile, "%8.3f %8.3f %10.5f  %2d  %7.3f %5.3f  %5.3f %5.3f %5.3f %5.3f  :  %f %f\n", star->x, star->y, starFlux, 0, source->psfMag, source->psfMagErr, axes.major, axes.minor, axes.theta, par8, model->params->data.F32[PM_PAR_I0], radius);
 
 	// add the sources to the source array