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Hi,
I was wondering if anyone knows how to specify a background region near a star (for instance having a box of a certain area to the right or left of the target/comparison star). My problem is that both my target and comparison stars are both near the edge of the ccd field of view since the ccd I was using has a very narrow field of view (about 3.8 arcmin.). I have collect 680 images of GJ 436 and I'm trying to produce a light curve during which GJ 436b transited across GJ 436. Both MaximDL and IRAF have been giving me issues when I try to auto tag the target and comparison star. Both programs don't like how the stars are near the edge and that there is not much background on one side of each of the stars. The stars also drift up and down along the field of view a bit but stay completely within the field of view and in MaximDL the tagging seems to lose the centroids after about 15 or so images. If anyone can help please get back to me as soon as possible.
Thanks,
Brett Addison

Hello,I'm not sure if one of the DIGIPHOT packages, say APPHOT, has the option for uncentered sky regions. The most likely task would be polyphot but my quick reading of the help file doesn't suggest this is possible.The task that will do this is in the external GUIAPPS package. The subpackage XAPPHOT is for photometry and the tasks XGUIPHOT or XGPHOT allow independent skies. The GUI task can be quite useful for complex interactive photometry situations such as you are dealing with.Yours,
Frank Valdes