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Roger,
To answer your initial question - its the required precision, versus all the mechanical errors / tolerances of the interacting gear - that makes this economically unachievable.
To get a rough alignment - isn't too challenging. But to get within say 30 arc seconds of your celestial pole, and account for all the flexures and non perfect orthonogality of your OTA components, and account for seeing variations - requires human intervention and a fuzzy logic system.
Simple example - how level can you get your mount. Can you think of a way to get your mount level to within 20 arc seconds. Now also ask is the base of your mount perfectly level in all directions to within a micro metre? I can't think of how one might get the base of a mount level to better than 5 arc minutes of true level.
Next is your OTA perfectly flat on your mount, or is its light path only within 2-3 arc minutes of aligned to the mount holding it?
Do any of the components of your rig flex by more than a few arc minutes or tens of arc seconds - and does this vary with elevation of the target?
Close to isn't too hard to achieve, but the high precision and rigidity of all the interacting components required for long duration, long focal length imaging is very, very exacting.
Look at Tpoint - it may model hundred of stars to account for pointing, tracking, flexure and non-orthonogality of your rigs' components - and it has tens of interacting variables and fitting methods.
Bottom line - the precision required exceeds the economic capability / cost point of the gear amateurs consume.
Matthew
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