How to open an animate popup window

I opened a pop up window using javascript :
The javascript function is here
 <script type="text/javascript">
        function strgetOperation() {
            var a = $("[id$='txtOperation']").val();
            window.open("Reports/Smt_ThreadConsumptonReportWindow.aspx?Names=" + a + "", "mywindow", "status=1,toolbar=1, width=900px, height=600px,left=250,top=100");
         }
         </script>
I want this new window will be opened center but it comes from right side of the screen. Actually I want to give it
some animate effect. Please help me.