[Shiraz (Ray)]

very high res image Paul - nice result.

just ran both systems through the spreadsheet. It agrees with your observation - with 20 minute subs on both, your system requires ~6x the time to get to the same depth in Ha.

As Colin pointed out, the f8/9micron and f3.8/4.5micron optics configurations are essentially equivalent, but your 11002 has about half the Ha QE of the 694 so you need 2x the exposure to compensate. The biggest killer though is that the 11002 has about double the read noise of the 694 and, since neither system is sky limited at 20 minutes under dark skies, the read noise makes a real difference - you need an extra ~3x exposure to compensate. You don't have many options to do anything about this, short of using much longer subs so that you introduce less read noise. However, you would need maybe 10 hour subs to really help a lot, so that has practical and dynamic range limitations. A camera with lower read noise would help, but it must have ~9 micron pixels to match the rest of your system. The only solutions I can think of would be one of the Sony 694/814 chipped cameras used in 2x2 bin to get large pixels (but only 1.5/2mp) - or maybe even a ZWO/QHY 16mp CMOS camera with software binning for 4mp. Neither would be much good for wider fields, but good for smaller objects such as PNs. If you want to try this approach, let me know - you can experiment with my 694 if that would help. With the 694 in bin2, you would get back the missing 6x factor using your existing scope.