Index: trunk/Ohana/src/opihi/cmd.astro/jdtolst.c
===================================================================
--- trunk/Ohana/src/opihi/cmd.astro/jdtolst.c	(revision 40376)
+++ trunk/Ohana/src/opihi/cmd.astro/jdtolst.c	(revision 41379)
@@ -23,10 +23,10 @@
   char *long_str = get_variable ("LONGITUDE");
   if (!long_str) {
-    gprint (GP_ERR, "please define $LONGITUDE\n");
+    gprint (GP_ERR, "please define $LONGITUDE (decimal hours, west positive)\n");
     FREE (OutputName);
     return FALSE;
   }
   double longitude = atof (long_str);
-  if (VERBOSE) gprint (GP_ERR, "using longitude of %f\n", longitude);
+  if (VERBOSE) gprint (GP_ERR, "using longitude of %f (decimal hours, west positive)\n", longitude);
   free (long_str);
 
@@ -87,4 +87,97 @@
   gprint (GP_ERR, "  (JD) may be a number or a vector.\n");
   gprint (GP_ERR, "  if (JD) is a vector, (output) must be supplied and is used as the name of the output vector \n");
+  gprint (GP_ERR, "  $LONGITUDE must be set (decimal hours, west positive)\n");
   return (FALSE);
 }
+
+# define MJD_OFFSET 2400000.5
+
+int mjdtolst (int argc, char **argv) {
+
+  int N;
+  Vector *mjdvec, *outvec;
+
+  int VERBOSE = FALSE;
+  VERBOSE = FALSE;
+  if ((N = get_argument (argc, argv, "-v"))) {
+    VERBOSE = TRUE;
+    remove_argument (N, &argc, argv);
+  }
+
+  char *OutputName = NULL;
+  if ((N = get_argument (argc, argv, "-output"))) {
+    remove_argument (N, &argc, argv);
+    OutputName = strcreate (argv[N]);
+    remove_argument (N, &argc, argv);
+  }
+  if (argc != 2) goto syntax;
+
+  char *long_str = get_variable ("LONGITUDE");
+  if (!long_str) {
+    gprint (GP_ERR, "please define $LONGITUDE (decimal hours, west positive)\n");
+    FREE (OutputName);
+    return FALSE;
+  }
+  double longitude = atof (long_str);
+  if (VERBOSE) gprint (GP_ERR, "using longitude of %f (decimal hours, west positive)\n", longitude);
+  free (long_str);
+
+  if (ISNUM(argv[1][0])) {
+
+    char *endptr;
+    double mjd = strtod (argv[1], &endptr);
+    if (endptr == argv[1]) {
+      gprint (GP_ERR, "error interpretting %s as a number\n", argv[1]);
+      FREE (OutputName);
+      return FALSE;
+    }
+
+    double lst = ohana_lst (mjd + MJD_OFFSET, longitude);
+
+    if (OutputName) {
+      set_variable (OutputName, lst);
+      FREE (OutputName);
+      return (TRUE);
+    }
+    
+    gprint (GP_ERR, "lst: %f\n", lst);
+    return (TRUE);
+  }
+
+  if (!OutputName) {
+    gprint (GP_ERR, " if (MJD) is a vector, -output must be supplied\n");
+    return FALSE;
+  }
+
+  if ((mjdvec = SelectVector (argv[1], OLDVECTOR, TRUE)) == NULL) {
+    FREE (OutputName);
+    return FALSE;
+  }
+
+  if (mjdvec->type != OPIHI_FLT) {
+    gprint (GP_ERR, " (MJD) must be of type FLOAT\n");
+    FREE (OutputName);
+    return FALSE;
+  }
+
+  if ((outvec = SelectVector (OutputName, ANYVECTOR, TRUE)) == NULL) {
+    FREE (OutputName);
+    return FALSE;
+  }
+
+  ResetVector (outvec, OPIHI_FLT, mjdvec[0].Nelements);
+
+  for (int i = 0; i < mjdvec[0].Nelements; i++) {
+    double lst = ohana_lst (mjdvec->elements.Flt[i] + MJD_OFFSET, longitude);
+    outvec->elements.Flt[i] = lst;
+  }
+  FREE (OutputName);
+  return TRUE;
+
+ syntax:
+  gprint (GP_ERR, "USAGE: mjdtolst (MJD) [-output name]\n");
+  gprint (GP_ERR, "  (MJD) may be a number or a vector.\n");
+  gprint (GP_ERR, "  if (MJD) is a vector, (output) must be supplied and is used as the name of the output vector \n");
+  gprint (GP_ERR, "  $LONGITUDE must be set (decimal hours, west positive)\n");
+  return (FALSE);
+}