diff --git a/applications/smurf/defaults/smurf_makemap.def b/applications/smurf/defaults/smurf_makemap.def
index 44bfa9b9a2c..46a2a42c354 100644
--- a/applications/smurf/defaults/smurf_makemap.def
+++ b/applications/smurf/defaults/smurf_makemap.def
@@ -95,6 +95,12 @@ ast.mapspike = 10
 #               masking for the FLT and/or COM models, since it allows a
 #               reasonable mask to be formed before subtracting off the
 #               first estimate of the astronommical signal.
+#
+#               If ast.skip is set to a negative value, it gives the
+#               largest number of iterations to perform and indicates
+#               that the AST model should be skipped on all of them. In
+#               this case the value supplied for parameter "numiter" is
+#               ignored.
 ast.skip = 0
 
 #-----------------------------------------------------------------
diff --git a/applications/smurf/libsmf/smf_calcmodel_ast.c b/applications/smurf/libsmf/smf_calcmodel_ast.c
index 11a696a09d8..a4e87a9fffd 100644
--- a/applications/smurf/libsmf/smf_calcmodel_ast.c
+++ b/applications/smurf/libsmf/smf_calcmodel_ast.c
@@ -310,6 +310,8 @@ void smf_calcmodel_ast( ThrWorkForce *wf __attribute__((unused)),
 
   /* We only do the rest if we are not skipping this iteration. */
   astMapGet0I( kmap, "SKIP", &skip );
+  if( skip < 0 ) skip = -skip;
+
   if( dat->iter < skip ) {
     dat->ast_skipped = 1;
     msgOutf( " ","   skipping AST model on this iteration (AST.SKIP=%d)\n",
diff --git a/applications/smurf/libsmf/smf_get_mask.c b/applications/smurf/libsmf/smf_get_mask.c
index b54214fa68a..1e0cfb91691 100644
--- a/applications/smurf/libsmf/smf_get_mask.c
+++ b/applications/smurf/libsmf/smf_get_mask.c
@@ -114,7 +114,7 @@
 *        rather than an error, since a null mask does not prevent a map
 *        being cerated.
 *     10-MAR-2014 (DSB):
-*        Allow source pixels defined by SNR to be accumulated from iteration 
+*        Allow source pixels defined by SNR to be accumulated from iteration
 *        to iteration, rather than replaced.
 *     {enter_further_changes_here}
 
@@ -259,6 +259,7 @@ unsigned char *smf_get_mask( ThrWorkForce *wf, smf_modeltype mtype,
    astMapGet0A( config, "AST", &akm );
    astMapGet0I( akm, "SKIP", &skip );
    akm = astAnnul( akm );
+   if( skip < 0 ) skip = -skip;
 
 /* Get the number of iterations over which the mask is to be applied. Zero
    means all. Return with no mask if this number of iterations has
diff --git a/applications/smurf/libsmf/smf_iteratemap.c b/applications/smurf/libsmf/smf_iteratemap.c
index a0e0d613d74..8113fa3919c 100644
--- a/applications/smurf/libsmf/smf_iteratemap.c
+++ b/applications/smurf/libsmf/smf_iteratemap.c
@@ -436,6 +436,10 @@
 *        performed that included an AST Model. Previously, termination
 *        could occur as soon as the initial AST-free iterations had been
 *        completed.
+*     2014-03-10 (DSB):
+*        Provide an option to skip the AST model on all iterations,
+*        terminating using the normal maptol criterion. This is done by
+*        setting a negative value for AST.SKIP.
 *     {enter_further_changes_here}
 
 *  Notes:
@@ -549,6 +553,7 @@ void smf_iteratemap( ThrWorkForce *wf, const Grp *igrp, const Grp *iterrootgrp,
                      size_t *numcnvg, int *iters, int *status ) {
 
   /* Local Variables */
+  int ast_skip;                 /* Number of iterations with no AST model */
   int bolomap=0;                /* If set, produce single bolo maps */
   size_t bstride;               /* Bolometer stride */
   double *chisquared=NULL;      /* chisquared for each chunk each iter */
@@ -805,8 +810,20 @@ void smf_iteratemap( ThrWorkForce *wf, const Grp *igrp, const Grp *iterrootgrp,
       /* Does maptol refer to mean map change or max map change? */
       astMapGet0I( keymap, "MAPTOL_MEAN", &maptol_mean );
 
+      /* A negative AST.SKIP value over-rides NUMITER. */
+      ast_skip = 0;
+      if( astMapGet0A( keymap, "AST", &kmap ) ) {
+         astMapGet0I( kmap, "SKIP", &ast_skip );
+         kmap = astAnnul( kmap );
+      }
+
       /* Number of iterations */
-      astMapGet0I( keymap, "NUMITER", &numiter );
+      if( ast_skip < 0 ) {
+         numiter = ast_skip;
+      } else {
+         astMapGet0I( keymap, "NUMITER", &numiter );
+      }
+
       if( numiter == 0 ) {
         *status = SAI__ERROR;
         errRep("", FUNC_NAME ": NUMITER cannot be 0", status);
@@ -2245,9 +2262,12 @@ void smf_iteratemap( ThrWorkForce *wf, const Grp *igrp, const Grp *iterrootgrp,
 
           /* Remember if no AST model was subtracted from the
              previous iteration. The dat.ast_skipped flag is updated
-             within smf_Calcmodel_ast, so we store its current value
-             now, before it is changed */
-          last_skipped = dat.ast_skipped;
+             within smf_calcmodel_ast, so we store its current value
+             now, before it is changed. It is used to decide on
+             convergence. But if all iterations are being skipped
+             we leave it set to zero to prevent it influencing the
+             termination critirion. */
+          if( ast_skip > 0 ) last_skipped = dat.ast_skipped;
 
           /* Estimate the AST model and subtract from the residuals. */
           smf_calcmodel_ast( wf, &dat, 0, keymap, NULL, dimmflags, status );