Bugs: dmfilth

A common error with dmfilth is to use an event file as input instead of an image. If an event file is used event file, the tool bins it into a very large image (8192 x 8192 for ACIS). With an image that large all the system memory can easily be exhausted -- especially if running on a 32bit machine which is limited to ~2Gb of memory per-application (regardless of how much memory is installed).

Ensure that an image is being used (dmlist the file will show either 'Table' or 'Image'). If using a table (ie event file) then it should be binned into an image first.

Instead of copying the WCS, it creates a new WCS in the output image taking values from the input image. This can result in sometime subtle differences (like comments, units being different) to fully incorrect results(eg when the input image does not define a tangent plane WCS projection).

dmfilth only works when the input image contains a non-linear world coordinate system that ties the X and Y axes together. Without this linkage, the coordinates used to check for inclusion in the source or background regions is wrong.