.sky {
    background-image: url("http://modulous.huffpost.com/2017/05/03/1493826877-sky2.jpg");
    background-repeat: no-repeat;
    background-size: cover;
  }

  .sky_no_contain{
    background-image: url("http://modulous.huffpost.com/2017/05/03/1493826877-sky2.jpg");
  }

  .sky_nav {
    background-image: url("http://modulous.huffpost.com/2017/05/03/1493840658-nav-bg-stars.png")
  }