Looks more like a groovy set of venetian blinds than a ducted fan
Seriously though, it looks like some sort of strobing effect. If you spread your fingers in front of the screen you are looking at, focus on the screen and then waggle your hand from side to side you will see you suddenly grow many more fingers. Something to do with the scan rate of the monitor and the motion of the fingers.
I reckon you have some strange confluence of prop speed and the horizontal scan rate of your camera.
One hopes the Captain was looking out for VFR traffic in E airspace while you were conducting your experiment.
