Index: trunk/Ohana/src/relphot/src/MosaicOps.c
===================================================================
--- trunk/Ohana/src/relphot/src/MosaicOps.c	(revision 41485)
+++ trunk/Ohana/src/relphot/src/MosaicOps.c	(revision 41486)
@@ -1330,4 +1330,7 @@
   }
 
+  // skip mosaics with too few good measurements
+  if (mark) return TRUE;
+
   fit1d_irls (psfStars, N);
   fit1d_irls (brightStars, Nbright);
Index: trunk/Ohana/src/relphot/src/TGroupOps.c
===================================================================
--- trunk/Ohana/src/relphot/src/TGroupOps.c	(revision 41485)
+++ trunk/Ohana/src/relphot/src/TGroupOps.c	(revision 41486)
@@ -952,4 +952,7 @@
   // do anything special with identified good nights?
   // (myTGroup->flags & ID_IMAGE_PHOTOM_UBERCAL)
+
+  // skip mosaics with too few good measurements
+  if (mark) return TRUE;
 
   fit1d_irls (psfStars, N);