--- ray/src/cv/tilt.cal	1991/08/22 08:43:47	1.1
+++ ray/src/cv/tilt.cal	2003/02/22 02:07:23	2.3
@@ -1,11 +1,10 @@
-{ SCCSid "$SunId$ LBL" }
-
+{ RCSid: $Id: tilt.cal,v 2.3 2003/02/22 02:07:23 greg Exp $ }
 {
 	tilt.cal - tilt data for IES luminaires
 }
 
 tilt_ang = Acos(Kz) / DEGREE;
-tilt_xang = Asin(Jy/sqrt(Jy*Jy+Jz*Jz)) / DEGREE;
+tilt_xang = if(Jy*Jy-FTINY, Asin(Jy/sqrt(Jy*Jy+Jz*Jz))/DEGREE, 0);
 
 tilt_ang2 = tri(tilt_ang, 90);
 tilt_xang2 = tri(tilt_xang, 90);