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Expensive mounts still need autoguiding to get round stars. Its somewhat of a myth to think you can get an expensive mount, align it and you can do 20 minute unguided round star exposures. Certainly not routinely even if someone can produce an image showing round stars which has been done up to 10 minutes or so. I have been able to get 10minutes sometimes with software assistance. But it would be errratic and not reliable.
There are elements of flexure, gear inaccuracies, imperfect balance etc etc.
The current most accurate mounts I believe use both high quality encoders and autoguiding as in high level AstroPhysics mounts.
Setting up every night and doing a fresh alignment can be painstaking.
One trick I used if you have a permanent pier was to do an accurate drift alignment and then I used a torch through the polar alignment scope in my Tak mount. It made a small spot on the ceiling of my observatory and I marked that with a piece of electrical tape.
Next time I setup the mount I simply adjusted it until that torch spot was on the tape and I was good to go.
A similar thing would be to have markers on pavement or pavers where you setup your mount outside then have a laser on the side of the mount shot a light to your fence or similar and leave a marker there at the correct spot. That would take a minutes to setup each time.
A good polar alignment is vital for even 10 minute exposures. It would be one of the first things to be sure of if you were having trouble with getting round stars despite using an autoguider.
Greg.
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