Thanks, Trevor and specially Justin. I know that it can be better, but I am still trying IRIS.
Repro - with DSS - IRIS - Photoshop
GSO 305 mm - Canon Rebel XT - 50 frames - 20 seg - iso 1600
medium scale:
http://i1063.photobucket.com/albums/..._ngc253_1k.jpg
large scale:
http://i1063.photobucket.com/albums/..._ngc253_2k.jpg
And removing gradients and noise, only:
medium scale:
http://i1063.photobucket.com/albums/...53repro_1k.jpg
large scale:
http://i1063.photobucket.com/albums/...53repro_2k.jpg