var degrees = 0; //max is 360 degrees
var degreeIncrement = 0.4; // rotation speed
var bgPosX = 0;
var bgPosY = 0; 
var bgPosXStart;
var bgPosYStart;
var scrollDelay = 50;
var firsttime = true;

function Scroller(){
    if (document.getElementById) {
        if (firsttime)
        {
            bgPosXStart = parseInt(document.getElementById("rotatephoto").style.backgroundPosition.split(" ")[0]);
            bgPosYStart = parseInt(document.getElementById("rotatephoto").style.backgroundPosition.split(" ")[1]);
            firsttime = false;
        }
        
        // increase degrees
        degrees = degrees + degreeIncrement;
        if (degrees > 360)
            degrees = degrees - 360;
        radians = degrees * Math.PI / 180;
        
        // calculate new X and Y
        bgPosX = Math.cos(radians) * 30;
        bgPosY = Math.sin(radians) * 12;
        
        document.getElementById("rotatephoto").style.backgroundPosition = (bgPosXStart + bgPosX)+ 'px ' + (bgPosYStart + bgPosY) + 'px'; 
        
        // increase degrees
        degrees = degrees + degreeIncrement;
        if (degrees > 360)
            degrees = degrees - 360;
        radians = degrees * Math.PI / 180;
        
        // calculate new X and Y
        bgPosX = Math.cos(radians) * 30;
        bgPosY = Math.sin(radians) * 12;
        setTimeout("Scroller()", scrollDelay); 
    } 
}