def set_radec(hdu_hdr, ra, dec, x, y):
    """
    Modify the Header to force RA/DEC value at a given x,y position

    Args:
        hdu_hdr: Header
        ra: float (deg)
        dec: float (deg)
        x: float
          x pixel position in the image
        y: float
          y pixel position in the image

    Returns:
        new_hdr: Header

    """
    new_hdr = hdu_hdr.copy()
    # Offset
    new_hdr['CRVAL1'] = ra
    new_hdr['CRVAL2'] = dec
    new_hdr['CRPIX1'] = x
    new_hdr['CRPIX2'] = y
    return new_hdr