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For round stars at 1000mm and 10-20 minute exposures I would have though PE of under a few ARC secs would be required. Whilst PE of 25 arc secs is probably fine for visual I can't see that being practical for imaging.
I guess 7 arc secs would be tops with an off axis guider and shorter guide exposures. After PEC that should be closer to 1 or 2 arc secs. My PMX is now running at under 1 arc sec and errors in guiding are more from seeing or not adjusting the settings to the autoguider to the optimum. My PME also is running at something around 1 arc sec after PEC.
The Mach 1 should be something like that I would imagine.
Normal upgrades for G11 is the Ovision worm. Not sure what it costs or what it brings the PE to. I have never used one so keep that in mind. But I have had several mounts and I can assure you getting a good one is the best thing you will ever spend in astrophotography. Being able to achieve round stars at 1200mm focal length is the starting point for astrophotography. If you can't get that every time you've got nothing.
A G11 from what I have read can be a good mount but will it achieve the above standard, routinely and reliably without modifications and endless chasing problems and lesser tolerances than are required for the above standard? That's what G11 owners need to tell you if its realistic or not. From what I have seen it is not. Not without mods, upgrades etc. Not worth it if you can afford to get the next quality up like your budget will allow.
An ED80 on a really nice mount would probably take better images than an AP scope on a poor mount. What's the point of sharp objects if the mounts tracking results in smeared details let alone eggy stars.
Its the biggest bugbear in imaging, round stars. Its hard enough even with top quality gear!!
Greg.
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