thank you, rust and comet for coments
As I said, I hope to obtain more red information free from interference of light pollution, and with less work in curves.
I know it will not act as a perfect Ha filter. But if it enhance the quality of information... it will be doing what I need.
About Canons, I didn't believe in "APOD" photos with them. See the stars, they haven't the same shape and sharp appearance as those with a good astronomic camera.
But, for who intends to register the object... they will work well. I have some photos of star cluster with better resolution than many others photos that I saw in Internet. For me, some ones are reference to these objects. At least, up to now, while nobody capture them with a better camera.
But, as the photos in Internet, they aren't beautiful ! They are images of content and not of visual impact.
http://jsmastronomy.30143.n7.nabble....-306-td91.html
http://jsmastronomy.30143.n7.nabble....048-td100.html