function updateSolpos() {
  var lon = document.getElementById('lon').value;
  var lat = document.getElementById('lat').value;
  var tz = document.getElementById('timez').value;
  var tilt = document.getElementById('tilt').value;
  var aspect = document.getElementById('aspect').value;
  var year = 2000;
  document.getElementById('msgdiv').innerHTML="Calculating and Loading Solar Position...";
  http.open("GET", solposurl + "?lon=" + lon + "&lat=" + lat + "&tz=" + tz + "&year=" + year + "&tilt=" + tilt + "&aspect=" + aspect, true);
  http.onreadystatechange = handleHttpResponse_solpos;
  http.send(null);
}