jQuery UI dialog positioning : adjust position top by 20px -

Question

I have a dialog that gets filled by an ajax call. I want to limit the max-height of dialog and also allow it to be scroll-able if this max-height is exceeded. The code below does exactly what I want.

The catch is I can not move the top of the dialog from the top position. I can move it left and right. I can't use center either as the dialog is displayed in a large scroll-able window. If I use firebug I can adjust the top property but cannot find where it is being set to zero.

$("#your-dialog-id").dialog({
    open: function(event, ui) {
        $(this).css({'max-height': 500, 'overflow-y': 'auto'});
    },
    autoOpen:false,
    modal: true,
    resizable: false,
    draggable: false,
    width: '690',
    closeOnEscape: true,
    position: 'top'
});

I want to adjust the dialog's y position so it is 20px from the top of the window. Any idea what I can do?

Answer 1

Changing the last value solved the problem:

position: ['center',20] 

http://jsfiddle.net/chrisloughnane/wApSQ/3