I poured the first bucket on them around 12:15 and there were screams and "Aaaugh! Fücking cünt!" yelled up. They didn't get the message, so I threw down a few more buckets at various intervals. They kept on laughing and yelling each time, so finally when it was getting close to 1:30 I scooped some cat turds out of the litter box and poured them down. There was silence, although several minutes later my dog started going crazy about a noise out in the hall; apparently someone had run up the stairs to see what apartment the turds came from. I know they could have looked up to see which window the light was coming from, but even if they know they're not likely to complain to the building management.
Sorry, no pix; I realize if I had been out they could have kept going all night long, but I know this noise bothers other people too, and not just in our building. Why couldn't they take the party indoors?