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  • $\begingroup$ What programming language do you work in? Furthermore, it is not entirely clear to me what you want as output, and I am unfamiliar with this 'nuproducts' tool. Why are the degrees, in which you have converted the pixel coordinates as you say in the EDIT, unsufficient? $\endgroup$ Commented Dec 7, 2017 at 12:19
  • $\begingroup$ I'm working in Julia now. Basically, NuSTAR data has to be calibrated before it's suitable for scientific analysis and there are a few stages to that calibration, one of the stages requires you to select a source region (as a .reg file, usually created by manually selecting an area using DS9) before you get the final fully calibrated/cleaned data. The FITS files store data as X Y pixel coordinates, but the region file needs to be in WCS, so I convert X, Y to FK5 angles. Problem now is that for converting the angle I get in degrees (which is correct) to hh:mm:ss is different to what DS9 outputs $\endgroup$ Commented Dec 7, 2017 at 12:22
  • $\begingroup$ How much is the discrepancy between DS9 output and what you get? $\endgroup$ Commented Dec 7, 2017 at 15:07
  • $\begingroup$ Aha, figured out what I did wrong, I was being stupid and converting degrees to h:m:s as if they were angles on a circle, which doesn't work for right-ascension since it goes from -90 to 90, not 0 to 360. Now that I've fixed it (here's a notebook where it works) it's still a bit off around 10^-5, but I guess that's just some floating point errors adding up along the way. $\endgroup$ Commented Dec 7, 2017 at 16:22