Just to pick up on Rick's point, here is a quote from Juan:
"Don't use the BatchPreprocessing script to integrate your light frames. In most cases, BatchPreprocessing does a fine job for generation of master calibration frames, image calibration and registration. However, integration of light frames is a critical process requiring manual intervention to fine tune pixel rejection and image combination parameters. The integrated output of BatchPreprocessing can be used as a quick preview of the image that can be achieved, but it is not the optimal image by any means, and many times you're quite likely to get a grossly wrong result (e.g., invalid rejection of plane and satellite trails, etc.)."
Seems pretty definitive to me, IMHO,
Jim