A further experiment with the ASI120MM and filter wheel set. This is 600RGB+700L all at 2 second exposure time, through the LX200 unguided. I've come to the conclusion that the Meade DSI is just too slow for really high quality guiding, which means that unless I want to go back to using the Canon DSLR as the main imaging camera (I don't), I'm time-limited on exposures. There was one hell of a lot of drift during the imaging run - not sure why, I guess that I need some better quality PEC training - but the combination result isn't as bad as I thought it would be. The main lessons I'm learning are that you need to refocus and recenter between filter switches and that I need to save up for another ZWO camera, so I can use the 120MM for guiding (it's amazingly effective) and a new camera for the actual imaging.
Anyway, M42 is always a popular target, and I'm familiar enough with it to know if I'm getting reasonable results or not. I'm not 100% happy with this result, but both the dynamic range and the overall image quality is at least as good as the DSLR results from last year. Once again, the cry of "more data needed!" goes up from my workstation...but it's all good prgress!