The light source was a glowstick like the ones divers use underwater. It's really a nice toy and an interesting light source for photography. While playing with that glowstick I found a dead midge (wasn't a spider) on my ledge. I didn't kill the midge for the photo (never would do that) but despite it lived well from my blood (*grrr*) it seems that was not enough. Anyway, somehow the idea formed in my mind to take a stance against nuklear energy by showing that radioactive material kills us. Shocking! :-)
@ambaker: I really enjoyed your explanations. Special thanks to you! But I think people will believe the fake radioactivity like I presented it in the photo more than as if I would taken a photo of a real radioactivity effect like you described. Stange thing, isn't it?
Thank you all again for your comments. Not a single critical one! Please be more negative ;-)
Actually the Cherenkov effect is sort of an electric blue. Erie as hell as the glow floats on the surface. (The object does not glow, the glow is produced by the radiation slowing down in water. Which is probably more than you ever wanted to know. ) Nice depth of field, great effect, and I particularly like the dead bug for atmosphere. 8