clusters.js

 var sizes = [53, 56, 66, 78, 90];
 var mcStyles = [];
 for (var i = 0, size; size = sizes[i]; i++) {
     mcStyles.push({
         url: '/static/img/markers/m' + (i + 1) + '.png',
         height: size,
         width: size
     });
 }
 var mcOptions = {
     gridSize: 50,
     maxZoom: 10,
     enableRetinaIcons: true,
     minimumClusterSize: 4
     minimumClusterSize: 4,
     styles: mcStyles
 };
 map = new google.maps.Map(element[0], mapOptions);
 mc = new MarkerClusterer(map, [], mcOptions);