I use a broadband Hutech LPS2 light pollution filter. Works very well. Although I'm imaging from reasonably dark skies, there is a limit to exposure time dictated by skyglow and the small amount of light pollution from town lights. The Hutech filter allows me to easily double my exposure times and some! I routinely take 10min RGB subs but have pushed it to 15mins on occasion.
http://www.sciencecenter.net/hutech/idas/lps.htm
For narrowband stuff I use more specific filters.
Astronomik EOS clip-in filters - 12nm Ha and 12nm OIII filters.
I'm pretty happy with these too considering I'm using them on a DSLR.
Here's the Tarantula Nebula region I imaged with these filters...
Ha version...
http://s327.photobucket.com/albums/k...rrent=25-1.jpg
OIII version...
http://s327.photobucket.com/albums/k...current=26.jpg
Product info...
http://www.astronomik.com/en/eos_clip-filters.html
But, obviously 2" filters are available for both of these filters.
Hope some of my waffle helps!!
Doug