Index: trunk/Ohana/src/opihi/cmd.astro/cgrid.c
===================================================================
--- trunk/Ohana/src/opihi/cmd.astro/cgrid.c	(revision 26258)
+++ trunk/Ohana/src/opihi/cmd.astro/cgrid.c	(revision 29001)
@@ -153,4 +153,12 @@
   SetVector (&Yvec, OPIHI_FLT, NELEMENTS);
   
+  { // sanity check
+    float Nelem;
+    Nelem = 180.0 / minorRA;
+    if (!isfinite(Nelem) || (fabs(Nelem) > 10000)) { fprintf (stderr, "absurd cgrid spacing %f\n", minorRA); return FALSE; }
+    Nelem = 180.0 / minorDEC;
+    if (!isfinite(Nelem) || (fabs(Nelem) > 10000)) { fprintf (stderr, "absurd cgrid spacing %f\n", minorDEC); return FALSE; }
+  }
+
   /***  do consecutive RA lines, first increasing **/
   OnPic = TRUE;