This is certainly impressive Marc. An 11" F/1.8 system has super astrograph written all over it. The initial results do show promise given such short exposure times and arcsec/pixel sampling remains good. Do you have a 10nm or higher Ha filter? F/1.8 is quite a fast light cone that may cause a shift from the typically centered 656.3nm for Ha which would alter the filters efficiency (transmission). Not sure if you've done any research into fast astrographs, but there is some good reading here that describes the fast light cone concern -
http://www.hbastro.com/Telescopes/Fa...derations.html
Would be keen to see traditional RGB results. Looking forward to seeing more of your imaging adventures with this gear.