<script type="text/javascript">
  var canSee = true;
  var scale = 0.50;
  var h = $(window).height();


$(window).scroll(function() {

    if ($(this).scrollTop() > h * scale && canSee) {
        $("#logo").velocity(
				    {
				      backgroundPositionY: "-3402px"
				    }, {
				      easing: [ 54 ],
				      duration: 1350,

				    });

        canSee = false;
    } else if ($(this).scrollTop() <= h * scale && !canSee) {
        $("#logo").velocity(
				    {
				      backgroundPositionY: "0px"
				    }, {
				      easing: [ 54 ],
				      duration: 1350,

				    });

        canSee = true;
    }
});
</script>