def pix_coord(self, pix_coord):
        """
        :type pix_coord: list
        :param pix_coord: an x,y pixel coordinate, origin = 1
        """
        try:
            pix_coord = list(pix_coord)
        except:
            pass
        if not isinstance(pix_coord, list) or len(pix_coord) != 2:
            raise ValueError("pix_coord needs to be set with an (x,y) coordinate pair, got {}".format(pix_coord))
        x, y = pix_coord
        if not isinstance(x, Quantity):
            x = float(x) * units.pix
        if not isinstance(y, Quantity):
            y = float(y) * units.pix
        self._pix_coord = x, y
:type pix_coord: list
        :param pix_coord: an x,y pixel coordinate, origin = 1