Did you ever think if makes sense to use a H-alpha filter with your DSLR?
-Your not sure because your astronomical-friends tell you that you will have 1/4 of the resolution only?

Trevor Jones of astrobackyard.com gives you a very helpfull start in emission line imaging with a DSLR.
Enjoy helpfull advise and a new video to learn why an H-alpha is the most important filter you should have in your toolbox of astrophotography accessories.