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Hello,Is there a way to use external object masks with XDIMSUM? I will be reducing data of a field for which I already have a deep image. The idea is from the deep image to create an accurate object mask. When the new images are obtained, the mask will be registered to each individual image and used to achieve better sky subtraction. Can this be done within XDIMSUM? Or there are other packages more suitable for this task (Gemini)?Vallery

Hello Vallery,XDIMSUM is mainly a collection of complex scripts. I don't think there is an easy way to do what you want with this package through functionally it is doing exactly what you are thinking.I am not aware of any "canned" tool that does what you want. I think the question you are asking is how to go back from a mask derived from a stacked image to masks for specific images used in the stack. If the images needed to be resampled, particularly with rotations or higher order distortion functions, then going back is not easy. If the deep image was made with shift and add then registering a mask back to the individual images should not been too hard to do using normal image tasks.In any case, this is a general image processing problem and the tools do exist but using them and understanding them may be tricky. If you started with accurate world coordinates when were updated during the registration and stacking process then matching a mask back to some other image may be not too hard with a task like mscimage where you specify a reference image for resampling an image to match.I'm sorry if this is not very specific guidance.Yours,
Frank Valdes