--- ray/src/gen/gendaymtx.c	2014/10/26 17:37:34	2.18
+++ ray/src/gen/gendaymtx.c	2015/09/02 22:52:04	2.21
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: gendaymtx.c,v 2.18 2014/10/26 17:37:34 greg Exp $";
+static const char RCSid[] = "$Id: gendaymtx.c,v 2.21 2015/09/02 22:52:04 greg Exp $";
 #endif
 /*
  *  gendaymtx.c
@@ -86,6 +86,7 @@ static const char RCSid[] = "$Id: gendaymtx.c,v 2.18 2
 #include <string.h>
 #include <ctype.h>
 #include "rtmath.h"
+#include "resolu.h"
 #include "platform.h"
 #include "color.h"
 #include "resolu.h"
@@ -393,7 +394,13 @@ main(int argc, char *argv[])
 			break;
 		case '5':			/* 5-phase calculation */
 			nsuns = 1;
-			fixed_sun_sa = 6.797e-05;
+			fixed_sun_sa = PI/360.*atof(argv[++i]);
+			if (fixed_sun_sa <= 0) {
+				fprintf(stderr, "%s: missing solar disk size argument for '-5' option\n",
+						argv[0]);
+				exit(1);
+			}
+			fixed_sun_sa *= fixed_sun_sa*PI;
 			break;
 		default:
 			goto userr;