Hi Peter,
in the beginners Astrophotography section are a few recent articles about the filter. I have one but didnīt manage to get suitable images so far with it. Part of the problem is postprocessing and apparently the right exposure time relative to the apperture of the imaging scope. But Rowland has had some success with it.
http://www.iceinspace.com.au/forum/showthread.php?t=65256