A centroiding method is provided for an optical tracking system including a laser used for countermeasuring purposes in which a pencil thin laser beam is accurately positioned onto a target through the use of centroiding techniques for ascertaining the position not only of the target but also the laser beam, with the centroiding techniques resulting in a sub-pixel level resolution. The sub-pixel resolution permits utilization of smaller cost-effective focal plane arrays by giving the small focal plane array a resolution associated with much larger focal plane arrays.