If your Astronomik filters cause halos in your images then read this:
http://www.astronomik.com/en/astronomik_halo_free_filter_halo_problem.html
Basically, you send them an example halo image showing the problem (plus some important shooting data) and if they agree the filter caused it then it will be replaced by one of their new "non-halo" filters.
Mark
Nice that they have had the balls to admit to an issue and set about resolving it to customers satisfaction. You don't see that very often nowadays.
I agree Mike, it's to their credit that they've decided to do that and to filters over 2-3 years old too.
Have just received a brand new set of Astronomik 1.25" 'No Halo" LRGB, Ha and OIII (had sold the SII) as replacements for my existing Halo producing filters. I must say, I'm very impressed with the service and speed with which Astronomik sent them and their professional attitude to the issue. All I have to do now is to send back the old filters and job done.
Robert