I owned and tested both the CGEM and Atlas mount side by side. I still have the CGEM. I found that the accuracy of the CGEM with a 2+2 alignment was dead on accurate, while the 3 star alignment with the Atlas was within the field of view of a wide field eyepiece, meaning it was not quite as accurate. One of the big issues for me though was that the CGEM offered more alignment star choices than the Atlas. This can be a issue if you have a lot of trees or obstructions in your observing area like I do. There were a few times when I could not find three alignment stars with the Atlas.
@Patrick thx for your valuable feedback. Seems logical what you said and I know Celestron software is better.
What keeps me away from CGEM unfortunately is its weight, cogging issue and DEC issue which is hardware related. Otherwise Celestron software attracts me more than Skywatcher.
Without beeing able to compare Celestron and Skywatcher mounts I feel that software difference in respect of GOTO resides in polar alignment. I feel that Skywatcher needs much better polar alignment for precise GOTO and Celestron is much more forgiving because its software computes better human error in this process due to different math formulas and more callibration stars. When coming down to photography I suppose both mounts need almost as accurate polar alignment for longer exposure and maybe in this case the software difference fades away.
Still this difference in computing precision could be important when ASPA because Skywatcher I think can not compute as well Celestron the polar alignment error and maybe it needs more itterations to reach Celestron's precision. Am I thinking correctly?
Patrick, how scrupulous were you with polar alignment with Skywatcher when you said the object was to the border of the FOV and scope and eyepiece have you been using?
I generally put Polaris in the middle of the polar scope with CG5-GT and I do 2+2 star alignment.
@Uncle Rod maybe I have too much expectations from AZ mode but I was thinking at 1-2 minutes exposures with C11 at F/3 for video astronomy. For photograhpy I would be using EQ mode only with C11 at F/6 on AZ-EQ6 for exposures of up to 5 minutes guided. Am I still crazy?