docs: def reference_source_point(self):
          """
          The location of the source in the reference image, in terms of the
          current image coordinates.
          """
          xref = isinstance(self.xref, Quantity) and self.xref.value or self.xref
          yref = isinstance(self.yref, Quantity) and self.yref.value or self.yref
  
          return xref + self.x_ref_offset, yref + self.y_ref_offset