Index: trunk/ppSim/src/ppSimLoadStars.c
===================================================================
--- trunk/ppSim/src/ppSimLoadStars.c	(revision 14463)
+++ trunk/ppSim/src/ppSimLoadStars.c	(revision 14531)
@@ -22,4 +22,7 @@
     float radius = 0.5 * PS_MAX(bounds->x1 - bounds->x0, bounds->y1 - bounds->y0) * scale;
     psFree(bounds);
+
+    float x0fpa = 0.5*(bounds->x0 + bounds->x1);
+    float y0fpa = 0.5*(bounds->y0 + bounds->y1);
 
     psMetadataAdd(astroRecipe, PS_LIST_TAIL, "RA_MIN",  PS_DATA_F32 | PS_META_REPLACE, "", ra0 - radius);
@@ -47,11 +50,11 @@
 
 	// Convert to x,y position on tangent plane, in pixels
-	float div = sin(star->ra) * sin(dec0) + cos(star->dec) * cos(dec0) * cos(star->ra - ra0) / scale;
+	float div = (sin(star->ra) * sin(dec0) + cos(star->dec) * cos(dec0) * cos(star->ra - ra0)) * scale;
 	float xi = cos(star->dec) * sin(star->ra - ra0) / div;
 	float eta = (sin(star->dec) * cos(dec0) - cos(star->dec) * sin(dec0) * cos(star->ra - ra0)) / div;
 
-	// Apply rotation
-	star->x = cos(pa) * xi - sin(pa) * eta;
-	star->y = sin(pa) * xi + cos(pa) * eta;
+	// Apply rotation, make FPA center of boresite
+	star->x = cos(pa) * xi - sin(pa) * eta + x0fpa;
+	star->y = sin(pa) * xi + cos(pa) * eta + y0fpa;
 
 	// Convert magnitude to peak flux