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In my (or perhaps everyone's) version of daophot, I get .psg file as output from running psf. However, nstar's default group file input is .grp. I have had no trouble manually inputting the psg file, but would like to know if I can modify either psf or nstar so they take the same file format. I have a LOT of psf images to fit (200 down, probably another 200 to go), so I think doing this might be worth my time if it takes less than 2 hours.I know that you can make your own IRAF programs but I don't know how. I figure I can clone the program, find the place in the code that says grp and only change those three letters? How do I do this?Thanks!

I would still like to know how to do this.I am trying to do something along the lines of what is listed here:ftp://iraf.noao.edu/ftp/web/projects/sitemail/0933.htmlSo I went to
blah/blah/iraf/iraf/noao/digiphot/daophot/nstar/And found that on line 189 of file t_nstar.x, there was something promising. From what I can tell, I might only need to change "grp" to "psg" and done, so I did that. (can someone confirm this?)Now I'm stuck on the part where the change makes a difference. I -ahem- made the change directly in the original file (bad, I know, but at worst I can scp the files from another IRAF installation in my lab). I had no luck with mkpkg or redefine, but I am probably doing it wrong. What next?