Well, I'm not sure, but another possibility is that it is your eye, due to the micro-movements your eye makes to form a complete image. If the brightness of the spark varies as a function of time and is much faster than the rate at which your eyes move, then it could be that sometimes your eye is looking at one region during the brightest part of the spark and sometimes it is looking at a different region. This may happen so fast that persistence of vision causes it to appear as multiple brighter regions. On Fri, Apr 3, 2015 at 12:25 AM, David VanHorn wrote: > Room air. The source is a disruptive discharge coil. Current in a single > spark is more than an amp, very narrow pulses. Spherical electrodes. > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .