Peter,
You probably don't want to push your 1000D more than ISO-400. It's just not suited to astrophotography at that high an ISO. Turn off in-camera noise reduction, take your own dark frames, as well as flat frames, and flat dark frames.
10-minute sub-exposures ought to be good. You just need to take plenty of them.
It might also be worthwhile to take a bunch of 1-minute and 5-minute sub-exposures (as well as all related calibration frames (except for flats)), too, to manually mask in the region over Alnitak, the nuisance that it is.
I used a 10" Schmidt-Newtonian and a modified Canon EOS-350D at 5-minute exposures, for my shot a couple of years ago. See here:
http://www.iceinspace.com.au/forum/s...ad.php?t=26125
Regards,
Humayun