[Solved]-Chart series fixed range-Highcharts

everytime you add a point, i'd check if the 1st point was < however far back you want to go. if it is, remove it.

if (chart.series[0].data[0].x < time cutoff) {

    chart.series[0].data[0].remove();
}

since you're doing a consistant time interval, you should be safe with just checking the 1st point.

http://api.highcharts.com/highcharts#point.remove()

another option based on the comments above:

var bshift = false;
if(!bshift && chart.series[0].data[0].x < time cutoff)  
    bshift = true;
chart.series[0].addpoint(point, true, bshift);