Great picture of Orion. A picture of a bright object like the Orion nebula is not likely to improve from stacking.

I use IRIS 5.1 (free ware). Excellent, but the learning curve is steep. It registers N pictures and then adds them together, but I have never tried more than 15. My standard exposure time is 60 seconds. This way the loss is not too bad if a picture has to be eliminated because an airplane goes through. The result is saved as high quality jpeg and final image processing in Photoshop.

hha