Steve,
I bought a 2" badder Ha filter but there was all sorts of confusion when I bought it on line as the dollar had just crashed. Firstly, they didn't have any then the price was for a 1.25" and finally I received a 7nm instead of the 13nm I ordered. I knew I'd have trouble using it on my DSLR as soon as I saw it was a 7nm, and I did. Here's M42 with 15 minute subs @ 800. There's a lot missing from what I expected to see. I got it from
http://www.aoe.com.au/ .
I'm hoping this new mono camera I have coming will give better results.