Index: trunk/Ohana/src/relphot/include/relphot.h
===================================================================
--- trunk/Ohana/src/relphot/include/relphot.h	(revision 40385)
+++ trunk/Ohana/src/relphot/include/relphot.h	(revision 40386)
@@ -294,4 +294,6 @@
 int    PARALLEL_SERIAL;
 char  *MANUAL_UNIQUER;
+
+int    SKIP_PARALLEL_GROUPS;
 
 int    PARALLEL_REGIONS_MANUAL;
Index: trunk/Ohana/src/relphot/src/args.c
===================================================================
--- trunk/Ohana/src/relphot/src/args.c	(revision 40385)
+++ trunk/Ohana/src/relphot/src/args.c	(revision 40386)
@@ -134,4 +134,10 @@
     PARALLEL = TRUE; // -parallel-serial implies -parallel
     PARALLEL_SERIAL = TRUE;
+    remove_argument (N, &argc, argv);
+  }
+  SKIP_PARALLEL_GROUPS = 0;
+  if ((N = get_argument (argc, argv, "-skip-parallel-groups"))) {
+    remove_argument (N, &argc, argv);
+    SKIP_PARALLEL_GROUPS = atoi(argv[N]);
     remove_argument (N, &argc, argv);
   }
@@ -549,4 +555,5 @@
   PARALLEL_MANUAL = FALSE;
   PARALLEL_SERIAL = FALSE;
+  SKIP_PARALLEL_GROUPS = 0;
 
   HOST_ID = 0;
Index: trunk/Ohana/src/relphot/src/reload_catalogs.c
===================================================================
--- trunk/Ohana/src/relphot/src/reload_catalogs.c	(revision 40385)
+++ trunk/Ohana/src/relphot/src/reload_catalogs.c	(revision 40386)
@@ -180,4 +180,5 @@
   for (i = 0; i < Ngroups; i++) {
     // update only a group of unique machines at a time
+    if (i < SKIP_PARALLEL_GROUPS) continue;
     reload_catalog_parallel_group (&groups[i], sky, imageFile);
   }