docs: def pixscale(self):
          """Return the pixel scale of the detector, in arcseconds.
  
          This routine first attempts to compute the size of a pixel using the WCS.  Then looks for PIXSCAL in header.
  
          @return: pixscal
          @rtype: float
          """
          try:
              (x, y) = self['NAXIS1'] / 2.0, self['NAXIS2'] / 2.0
              p1 = SkyCoord(*self.wcs.xy2sky(x, y) * units.degree)
              p2 = SkyCoord(*self.wcs.xy2sky(x + 1, y + 1) * units.degree)
              return round(p1.separation(p2).to(units.arcsecond).value / math.sqrt(2), 3)
          except Exception as ex:
              logging.debug("Failed to compute PIXSCALE using WCS: {}".format(ex))
  
          return float(self['PIXSCAL'])