Index: /trunk/dvoTools/src/dvoMakeCorrLoop.c
===================================================================
--- /trunk/dvoTools/src/dvoMakeCorrLoop.c	(revision 41743)
+++ /trunk/dvoTools/src/dvoMakeCorrLoop.c	(revision 41744)
@@ -66,4 +66,9 @@
 	  continue;
 	}
+
+	// not all extensions are required to exist.  skip if not found
+	if (!psFitsMoveExtName (input->fits, inChip->hdu->extname)) {
+	  continue;
+	}
 	psImage *inImage = psFitsReadImage (input->fits, fullImage, 0);
 	assert (inImage);