Index: trunk/Mars/hawc/fresnellens_psf.C
===================================================================
--- trunk/Mars/hawc/fresnellens_psf.C	(revision 19932)
+++ trunk/Mars/hawc/fresnellens_psf.C	(revision 19933)
@@ -19,4 +19,11 @@
     const double D = 54.92;  // [cm] Diameter of the refractive surface
     const double F = 50.21;  // [cm] Nominal focal length of the lens
+    const double w = 0.01;   // [cm] Width of a single groove
+
+    // Tim used some unintentionally wrong values in his simulation:
+    // const double D = 50.21;   // [cm] Diameter of the refractive surface
+    // const double F = 49.833;  // [cm] calculated as D * (F/D) with D=50.21/54.92
+    // const double w = 0.05;    // [cm] Width of a single groove
+
     const double H = 0.25;   // [cm] Thickness of lens
     const double Z = F;      // [cm] camera position w.r.t. lens exit (see also MGeomCamFAMOUS!)