D..2 January, 2008 (AE Version 3.173b)

• For a long time now, a bug in CIAO has complicated the construction of masked exposure maps for use in the EXTRACT_BACKGROUNDS stage, leading to cropping of the background data. Brief discussion of this bug was added to this manual in several places in October, 2006. However, readers may have easily missed those references to the problem since some were in footnotes. Since the bug remains in the recently-released CIAO 4.0 and will probably be with us for a while longer, I've modified the ae_standard_extraction tool work around this bug (by adding small mask regions at the corners of the exposure map). If you choose to prepare masked exposure maps manually, §7.12 now describes in more detail the options you have for dealing with this bug.