I have the Astronmoik EOS CLS CCD clip, works very well when it is actually dark. Under moon light or low light level conditions, it tends to give a blue cast to all images if not used properly, camera adjustments, etc. Have done 15 mins under dark skies with good results. I think it is a good filter.
I also have narrow band filters for my DSI Pro 2 and EFW from Astronomik and they are fine, too.
