This evening, the moon sets early enough that many people should have the possibility to make moon-free observations of the sky brightness using the Loss of the Night app (Android) or Dark Sky Meter app (iPhone). The moon-free observing period stretches from about September 24-October 9 (exact dates depend on your latitude).
After October 9, the next observing periods this year will be:
October 23 - November 7
November 21 - December 6
December 20 - January 4 (2014)
The dates are based on Berlin sun/moon rise/set times, and will be slightly different depending on where you live and what time of night you intend to make your observation.
Please try to make observations especially in urban areas with lots of light pollution, and please encourage your friends in urban areas to do the same!