As Peter mentioned, you can get the 2" Ha Filters with a thread on them that you either screw onto the end of the UV/IR nosepiece of the QHY8 or the coma corrector if you use one. I use one.
Here's an example
This has the qhy8, uv/ir nosepiece, spacer, coma corrector, and LP filter screwed on. The Ha would screw on similarly. you may not need a coma corrector for your scope though.
http://www.flickr.com/photos/gus_sme...n/photostream/
Have a look at Eric's narrowband images from Sydney with a qhy8. very long integration time (20min subs), but great results
http://ejcruz.smugmug.com/Photograph...haBo3_L-XL.jpg
I'm planning on adding Ha to the QHY8 RGB images, still learning though.
and get an LP filter. I recently got one and was amazed with the difference.
again, you get the 2" threaded filters
without
http://alistairsam.wix.com/astronomy...23nj/image11wt
with
http://alistairsam.wix.com/astronomy...c23nj/image724
edit: the above are unprocessed 60second single frame with the qhy8.
They can be fiddly and sometimes not reliable in terms of drivers or banding or software errors, but once you install them correctly, they work well.