def send_coords(s, private_key, coords):
    """Send a SAMP notification to point at given coordinates."""
    import os
    message = {}
    message['samp.mtype'] = 'coord.pointAt.sky'
    message['samp.params'] = {}
    message['samp.params']['ra'] = str(coords[0])
    message['samp.params']['dec'] = str(coords[1])
    lockfile = os.path.expanduser('~/.samp')
    if not os.path.exists(lockfile):
        raise RuntimeError('A running SAMP hub was not found.')
    else:
        s.samp.hub.notifyAll(private_key, message)
