// Obtain latlng from mouse event
var latlng;
// Convert latlng to pixels
var px = project(latlng);
// Add pixel height offset to converted pixels (screen origin is top left)
px.y -= mypopup.maxheight/2
// Convert back to coordinates
latlng = unproject(px);
// Pan map
map.panTo(latlng,{animate: true});