Index: /branches/eam_branches/ohana.20190329/src/opihi/mana/deimos_mkslit.c
===================================================================
--- /branches/eam_branches/ohana.20190329/src/opihi/mana/deimos_mkslit.c	(revision 40770)
+++ /branches/eam_branches/ohana.20190329/src/opihi/mana/deimos_mkslit.c	(revision 40771)
@@ -109,5 +109,5 @@
 
       // set the sky in the entire window 
-      out[ix + iy*Nx] = sky ? sky->elements.Flt[iy] : 0.0;
+      out[ix + iy*Nx] = NAN;
 
       // equivalent coord in the profile:
@@ -117,4 +117,5 @@
 
       // a default value:
+      float vsky = sky ? sky->elements.Flt[iy] : 0.0;
       float vout = NAN;
 
@@ -140,5 +141,5 @@
       if (flux) vout *= flux->elements.Flt[iy];
 
-      out[ix + iy*Nx] += vout;
+      out[ix + iy*Nx] = vsky + vout;
     }
   }