Index: trunk/psphot/src/models/pmModel_STRAIL.c
===================================================================
--- trunk/psphot/src/models/pmModel_STRAIL.c	(revision 19880)
+++ trunk/psphot/src/models/pmModel_STRAIL.c	(revision 19881)
@@ -478,4 +478,5 @@
 {
     pmMoments *Smoments = source->moments;
+    pmPeak    *peak    = source->peak;
     psF32     *params  = model->params->data.F32;
 
@@ -484,7 +485,7 @@
     psEllipseMoments moments;
 
-    moments.x2 = PS_SQR(Smoments->Sx);
-    moments.y2 = PS_SQR(Smoments->Sy);
-    moments.xy = Smoments->Sxy;
+    moments.x2 = Smoments->Mxx;
+    moments.y2 = Smoments->Myy;
+    moments.xy = Smoments->Mxy;
     //sometimes these moment inputs are zero...why?
 
@@ -494,8 +495,9 @@
     shape = psEllipseAxesToShape(axes);
 
-    params[0] = Smoments->Sky;
-    params[1] = Smoments->Peak - Smoments->Sky;
-    params[2] = Smoments->x;
-    params[3] = Smoments->y;
+    params[PM_PAR_SKY]  = Smoments->Sky;
+    params[PM_PAR_I0]   = peak->flux;
+    params[PM_PAR_XPOS] = peak->xf;
+    params[PM_PAR_YPOS] = peak->yf;
+
     params[7] = 2 * axes.major;
     params[8] = axes.theta;
Index: trunk/psphot/src/models/pmModel_TEST1.c
===================================================================
--- trunk/psphot/src/models/pmModel_TEST1.c	(revision 19880)
+++ trunk/psphot/src/models/pmModel_TEST1.c	(revision 19881)
@@ -126,12 +126,23 @@
 {
     pmMoments *moments = source->moments;
+    pmPeak    *peak    = source->peak;
     psF32     *PAR  = model->params->data.F32;
 
+    psEllipseMoments emoments;
+    emoments.x2 = moments->Mxx;
+    emoments.y2 = moments->Myy;
+    emoments.xy = moments->Mxy;
+
+    // force the axis ratio to be < 20.0
+    psEllipseAxes axes = psEllipseMomentsToAxes (emoments, 20.0);
+    psEllipseShape shape = psEllipseAxesToShape (axes);
+
     PAR[PM_PAR_SKY] = moments->Sky;
-    PAR[PM_PAR_I0] = moments->Peak - moments->Sky;
-    PAR[PM_PAR_XPOS] = moments->x;
-    PAR[PM_PAR_YPOS] = moments->y;
-    PAR[PM_PAR_SXX] = PS_MAX(0.5, moments->Sx);
-    PAR[PM_PAR_SYY] = PS_MAX(0.5, moments->Sy);
+    PAR[PM_PAR_I0]   = peak->flux;
+    PAR[PM_PAR_XPOS] = peak->xf;
+    PAR[PM_PAR_YPOS] = peak->yf;
+    PAR[PM_PAR_SXX] = PS_MAX(0.5, M_SQRT2*shape.sx);
+    PAR[PM_PAR_SYY] = PS_MAX(0.5, M_SQRT2*shape.sy);
+    PAR[PM_PAR_SXY] = shape.sxy;
     PAR[PM_PAR_SXY] = 0.0;  // XXX we can get this right if we do the integral
 
Index: trunk/psphot/src/psphotBlendFit.c
===================================================================
--- trunk/psphot/src/psphotBlendFit.c	(revision 19880)
+++ trunk/psphot/src/psphotBlendFit.c	(revision 19881)
@@ -55,13 +55,11 @@
 
         // limit selection to some SN limit
-        // XXX this should use peak?
-        if (source->moments == NULL) continue;
-        if (source->moments->SN < FIT_SN_LIM) continue;
+        if (source->peak->SN < FIT_SN_LIM) continue;
 
         // XXX this should use peak?
-        if (source->moments->x < AnalysisRegion.x0) continue;
-        if (source->moments->y < AnalysisRegion.y0) continue;
-        if (source->moments->x > AnalysisRegion.x1) continue;
-        if (source->moments->y > AnalysisRegion.y1) continue;
+        if (source->peak->xf < AnalysisRegion.x0) continue;
+        if (source->peak->yf < AnalysisRegion.y0) continue;
+        if (source->peak->xf > AnalysisRegion.x1) continue;
+        if (source->peak->yf > AnalysisRegion.y1) continue;
 
         // if model is NULL, we don't have a starting guess
@@ -95,5 +93,5 @@
 	    if (psphotFitBlob (readout, source, sources, psf, maskVal, markVal)) {
 		source->type = PM_SOURCE_TYPE_EXTENDED;
-		psTrace ("psphot", 5, "source at %7.1f, %7.1f is ext", source->moments->x, source->moments->y);
+		psTrace ("psphot", 5, "source at %7.1f, %7.1f is ext", source->peak->xf, source->peak->yf);
 		Next ++;
 		continue;
@@ -102,5 +100,5 @@
 	    if (psphotFitBlend (readout, source, psf, maskVal, markVal)) {
 		source->type = PM_SOURCE_TYPE_STAR;
-		psTrace ("psphot", 5, "source at %7.1f, %7.1f is psf", source->moments->x, source->moments->y);
+		psTrace ("psphot", 5, "source at %7.1f, %7.1f is psf", source->peak->xf, source->peak->yf);
 		Npsf ++;
 		continue;
@@ -108,5 +106,5 @@
 	}
 
-        psTrace ("psphot", 5, "source at %7.1f, %7.1f failed", source->moments->x, source->moments->y);
+        psTrace ("psphot", 5, "source at %7.1f, %7.1f failed", source->peak->xf, source->peak->yf);
         Nfail ++;
 
Index: trunk/psphot/src/psphotChoosePSF.c
===================================================================
--- trunk/psphot/src/psphotChoosePSF.c	(revision 19880)
+++ trunk/psphot/src/psphotChoosePSF.c	(revision 19881)
@@ -474,8 +474,7 @@
         if (!(source->mode & PM_SOURCE_MODE_PSFSTAR)) continue;
 
-        // moments->Sx,Sy are roughly sigma_x,y
-        moments.x2 = PS_SQR(source->moments->Sx);
-        moments.y2 = PS_SQR(source->moments->Sy);
-        moments.xy = source->moments->Sxy;
+        moments.x2 = source->moments->Mxx;
+        moments.y2 = source->moments->Myy;
+        moments.xy = source->moments->Mxy;
 
         // limit axis ratio < 20.0
Index: trunk/psphot/src/psphotExtendedSourceAnalysis.c
===================================================================
--- trunk/psphot/src/psphotExtendedSourceAnalysis.c	(revision 19880)
+++ trunk/psphot/src/psphotExtendedSourceAnalysis.c	(revision 19881)
@@ -71,5 +71,5 @@
 		// all measurements below require the radial profile; skip them all
 		// re-subtract the object, leave local sky
-		psTrace ("psphot", 5, "failed to extract radial profile for source at %7.1f, %7.1f", source->moments->x, source->moments->y);
+		psTrace ("psphot", 5, "failed to extract radial profile for source at %7.1f, %7.1f", source->moments->Mx, source->moments->My);
 		pmSourceSub (source, PM_MODEL_OP_FULL, maskVal);
 		source->mode |= PM_SOURCE_MODE_SUBTRACTED;
@@ -81,7 +81,7 @@
 	if (doIsophotal) {
 	    if (!psphotIsophotal (source, recipe, maskVal)) {
-		psTrace ("psphot", 5, "failed to measure isophotal mags for source at %7.1f, %7.1f", source->moments->x, source->moments->y);
+		psTrace ("psphot", 5, "failed to measure isophotal mags for source at %7.1f, %7.1f", source->moments->Mx, source->moments->My);
 	    } else {
-		psTrace ("psphot", 5, "measured isophotal mags for source at %7.1f, %7.1f", source->moments->x, source->moments->y);
+		psTrace ("psphot", 5, "measured isophotal mags for source at %7.1f, %7.1f", source->moments->Mx, source->moments->My);
 		Nisophot ++;
 	    }
@@ -91,7 +91,7 @@
 	if (doPetrosian) {
 	    if (!psphotPetrosian (source, recipe, maskVal)) {
-		psTrace ("psphot", 5, "measured petrosian flux & radius for source at %7.1f, %7.1f", source->moments->x, source->moments->y);
+		psTrace ("psphot", 5, "measured petrosian flux & radius for source at %7.1f, %7.1f", source->moments->Mx, source->moments->My);
 	    } else {
-		psTrace ("psphot", 5, "measured petrosian flux & radius for source at %7.1f, %7.1f", source->moments->x, source->moments->y);
+		psTrace ("psphot", 5, "measured petrosian flux & radius for source at %7.1f, %7.1f", source->moments->Mx, source->moments->My);
 		Npetro ++;
 	    }
@@ -101,7 +101,7 @@
 	if (doKron) {
 	    if (!psphotKron (source, recipe, maskVal)) {
-		psTrace ("psphot", 5, "failed to measure kron mags for source at %7.1f, %7.1f", source->moments->x, source->moments->y);
+		psTrace ("psphot", 5, "failed to measure kron mags for source at %7.1f, %7.1f", source->moments->Mx, source->moments->My);
 	    } else {
-		psTrace ("psphot", 5, "measure kron mags for source at %7.1f, %7.1f", source->moments->x, source->moments->y);
+		psTrace ("psphot", 5, "measure kron mags for source at %7.1f, %7.1f", source->moments->Mx, source->moments->My);
 		Nkron ++;
 	    }
@@ -114,5 +114,5 @@
 		return false;
 	    } 
-	    psTrace ("psphot", 5, "measured annuli for source at %7.1f, %7.1f", source->moments->x, source->moments->y);
+	    psTrace ("psphot", 5, "measured annuli for source at %7.1f, %7.1f", source->moments->Mx, source->moments->My);
 	    Nannuli ++;
 	}
Index: trunk/psphot/src/psphotExtendedSourceFits.c
===================================================================
--- trunk/psphot/src/psphotExtendedSourceFits.c	(revision 19880)
+++ trunk/psphot/src/psphotExtendedSourceFits.c	(revision 19881)
@@ -163,8 +163,8 @@
               modelFit = psphotPSFConvModel (readout, source, modelType, maskVal, markVal, psfSize);
               if (!modelFit) {
-                  psTrace ("psphot", 5, "failed to fit psf-conv model for object at %f, %f", source->moments->x, source->moments->y);
+                  psTrace ("psphot", 5, "failed to fit psf-conv model for object at %f, %f", source->moments->Mx, source->moments->My);
                   continue;
               }
-              psTrace ("psphot", 4, "fit psf-conv model for %f, %f : %s chisq = %f\n", source->moments->x, source->moments->y, pmModelClassGetName (modelFit->type), modelFit->chisq);
+              psTrace ("psphot", 4, "fit psf-conv model for %f, %f : %s chisq = %f\n", source->moments->Mx, source->moments->My, pmModelClassGetName (modelFit->type), modelFit->chisq);
               Nconvolve ++;
               if (!(modelFit->flags & (PM_MODEL_STATUS_BADARGS | PM_MODEL_STATUS_NONCONVERGE | PM_MODEL_STATUS_OFFIMAGE))) {
@@ -176,9 +176,9 @@
               modelFit = psphotFitEXT (readout, source, modelType, maskVal, markVal);
               if (!modelFit) {
-                  psTrace ("psphot", 5, "failed to fit plain model for object at %f, %f", source->moments->x, source->moments->y);
+                  psTrace ("psphot", 5, "failed to fit plain model for object at %f, %f", source->moments->Mx, source->moments->My);
                   continue;
               }
               pmSourceCacheModel (source, maskVal);
-              psTrace ("psphot", 4, "fit plain model for %f, %f : %s chisq = %f\n", source->moments->x, source->moments->y, pmModelClassGetName (modelFit->type), modelFit->chisq);
+              psTrace ("psphot", 4, "fit plain model for %f, %f : %s chisq = %f\n", source->moments->Mx, source->moments->My, pmModelClassGetName (modelFit->type), modelFit->chisq);
               Nplain ++;
               if (!(modelFit->flags & (PM_MODEL_STATUS_BADARGS | PM_MODEL_STATUS_NONCONVERGE | PM_MODEL_STATUS_OFFIMAGE))) {
@@ -217,5 +217,5 @@
         if (minModel == -1) {
           // re-subtract the object, leave local sky
-          psTrace ("psphot", 5, "failed to fit extended source model to object at %f, %f", source->moments->x, source->moments->y);
+          psTrace ("psphot", 5, "failed to fit extended source model to object at %f, %f", source->moments->Mx, source->moments->My);
 
           // replace original model, subtract it
@@ -257,6 +257,6 @@
         psFree (modelFluxes);
 
-        psTrace ("psphot", 4, "best ext model for %f, %f : %s chisq = %f\n", source->moments->x, source->moments->y, pmModelClassGetName (source->modelEXT->type), source->modelEXT->chisq);
-        psTrace ("psphot", 5, "extended source model for source at %7.1f, %7.1f", source->moments->x, source->moments->y);
+        psTrace ("psphot", 4, "best ext model for %f, %f : %s chisq = %f\n", source->moments->Mx, source->moments->My, pmModelClassGetName (source->modelEXT->type), source->modelEXT->chisq);
+        psTrace ("psphot", 5, "extended source model for source at %7.1f, %7.1f", source->moments->Mx, source->moments->My);
 
         if (savePics) {
Index: trunk/psphot/src/psphotFakeSources.c
===================================================================
--- trunk/psphot/src/psphotFakeSources.c	(revision 19880)
+++ trunk/psphot/src/psphotFakeSources.c	(revision 19881)
@@ -10,9 +10,9 @@
         pmSource *source = pmSourceAlloc ();
         source->moments = pmMomentsAlloc ();
-        source->moments->x = 10;
-        source->moments->y = 10;
-        source->moments->Sx = 1;
-        source->moments->Sy = 1;
-        source->moments->Sxy = 0;
+        source->moments->Mx = 10;
+        source->moments->My = 10;
+        source->moments->Mxx = 1;
+        source->moments->Myy = 1;
+        source->moments->Mxy = 0;
         source->moments->Sum = 1000;
         source->moments->Peak = 100;
Index: trunk/psphot/src/psphotGuessModels.c
===================================================================
--- trunk/psphot/src/psphotGuessModels.c	(revision 19880)
+++ trunk/psphot/src/psphotGuessModels.c	(revision 19881)
@@ -59,6 +59,6 @@
 	    // these valuse are set in pmSourceModelGuess, should this rule be in there as well?
 	    if (source->mode &  PM_SOURCE_MODE_SATSTAR) {
-		modelEXT->params->data.F32[PM_PAR_XPOS] = source->moments->x;
-		modelEXT->params->data.F32[PM_PAR_YPOS] = source->moments->y;
+		modelEXT->params->data.F32[PM_PAR_XPOS] = source->moments->Mx;
+		modelEXT->params->data.F32[PM_PAR_YPOS] = source->moments->My;
 	    } else {
 		modelEXT->params->data.F32[PM_PAR_XPOS] = source->peak->xf;
Index: trunk/psphot/src/psphotModelTest.c
===================================================================
--- trunk/psphot/src/psphotModelTest.c	(revision 19880)
+++ trunk/psphot/src/psphotModelTest.c	(revision 19881)
@@ -143,11 +143,11 @@
     source->peak->value = source->moments->Peak;
 
-    fprintf (stderr, "sum: %f @ (%f, %f)\n", source->moments->Sum, source->moments->x, source->moments->y);
-    fprintf (stderr, "moments: %f, %f - %f\n", source->moments->Sx, source->moments->Sy, source->moments->Sxy);
+    fprintf (stderr, "sum: %f @ (%f, %f)\n", source->moments->Sum, source->moments->Mx, source->moments->My);
+    fprintf (stderr, "moments: %f, %f - %f\n", source->moments->Mxx, source->moments->Myy, source->moments->Mxy);
 
     psEllipseMoments moments;
-    moments.x2 = source->moments->Sx;
-    moments.y2 = source->moments->Sy;
-    moments.xy = source->moments->Sxy;
+    moments.x2 = source->moments->Mxx;
+    moments.y2 = source->moments->Myy;
+    moments.xy = source->moments->Mxy;
     psEllipseAxes axes = psEllipseMomentsToAxes (moments, 20.0);
 
Index: trunk/psphot/src/psphotMosaicSubimage.c
===================================================================
--- trunk/psphot/src/psphotMosaicSubimage.c	(revision 19880)
+++ trunk/psphot/src/psphotMosaicSubimage.c	(revision 19881)
@@ -38,5 +38,5 @@
 		newImage->data.F32[iy][ix] = subImage->data.F32[iy][ix] / peak;
 	    } else {
-		newImage->data.F32[iy][ix] = subImage->data.F32[iy][ix] / peak;
+		newImage->data.F32[iy][ix] = subImage->data.F32[iy][ix];
 	    }
 	}
Index: trunk/psphot/src/psphotSourceFits.c
===================================================================
--- trunk/psphot/src/psphotSourceFits.c	(revision 19880)
+++ trunk/psphot/src/psphotSourceFits.c	(revision 19881)
@@ -218,5 +218,5 @@
     if (source->type == PM_SOURCE_TYPE_DEFECT) return false;
     if (source->type == PM_SOURCE_TYPE_SATURATED) return false;
-    if (source->moments->SN < EXT_MIN_SN) return false;
+    if (source->peak->SN < EXT_MIN_SN) return false;
 
     // recalculate the source moments using the larger extended-source moments radius
@@ -331,8 +331,12 @@
     maskVal |= markVal;
 
+    // XXX this is really poor: if we don't have moments for the source, we have no guess.
+    // force the measurement?
+    psAssert (source->moments, "moments are re-calculated for any extended source");
+	
     // make a guess at the position of the two sources
-    moments.x2 = source->moments->Sx;
-    moments.y2 = source->moments->Sy;
-    moments.xy = source->moments->Sxy;
+    moments.x2 = source->moments->Mxx;
+    moments.xy = source->moments->Mxy;
+    moments.y2 = source->moments->Myy;
     axes = psEllipseMomentsToAxes (moments, 20.0);
 
@@ -380,6 +384,6 @@
     psphotCheckRadiusEXT (readout, source, EXT, markVal);
 
-    if ((source->moments->Sx < 1e-3) || (source->moments->Sx < 1e-3)) {
-        psTrace ("psphot", 5, "problem source: moments: %f %f\n", source->moments->Sx, source->moments->Sy);
+    if ((source->moments->Mxx < 1e-3) || (source->moments->Myy < 1e-3)) {
+        psTrace ("psphot", 5, "problem source: moments: %f %f\n", source->moments->Mxx, source->moments->Myy);
     }
 
Index: trunk/psphot/src/psphotSummaryPlots.c
===================================================================
--- trunk/psphot/src/psphotSummaryPlots.c	(revision 19880)
+++ trunk/psphot/src/psphotSummaryPlots.c	(revision 19881)
@@ -61,6 +61,6 @@
 	if (source->moments == NULL) continue;
     
-	xFaint->data.F32[nF] = source->moments->Sx;
-	yFaint->data.F32[nF] = source->moments->Sy;
+	xFaint->data.F32[nF] = source->moments->Mxx;
+	yFaint->data.F32[nF] = source->moments->Myy;
 	nF++;
     
@@ -68,6 +68,6 @@
 	if (source->moments->SN < 25) continue;
 
-	xBright->data.F32[nB] = source->moments->Sx;
-	yBright->data.F32[nB] = source->moments->Sy;
+	xBright->data.F32[nB] = source->moments->Mxx;
+	yBright->data.F32[nB] = source->moments->Myy;
 	nB++;
     }
@@ -160,7 +160,7 @@
 
 	psEllipseMoments moments;
-	moments.x2 = source->moments->Sx;
-	moments.y2 = source->moments->Sy;
-	moments.xy = source->moments->Sxy;
+	moments.x2 = source->moments->Mxx;
+	moments.xy = source->moments->Mxy;
+	moments.y2 = source->moments->Myy;
 
 	psEllipseShape shape;