I received this filter today so I 'dry tested; it, i.e. on street scenes and with high pressure sodium and metal halide lamps to test its performance. Because of cloudy and moonlit skies I cannot test in real life yet.
It looks really promising: the ubiquitous yellow sodium light is dimmed for at least four stops while daylight / starlight is dimmed for only one stop.
Here my preliminary test report:
http://www.northsouthsky.com/astronomik-cls.php