Quote:
Originally Posted by Merlin66
That's it - I feel this method is a bit like extreme drift alignment.
The first slew uses the location/time and sky cordinates to move the scope - if we were in perfect registration with the sky it would land on the target..by moving the mount in Alt/Az we are re-aligning the mount's axis to the sky...
Let me know what you think.
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Yep, I used to do a similar thing by first slewing to a star and loosening the clutches, centering the mount on the star, and then tightening the clutches. It's now redundant because I do an initial slew, plate solve the initial unknown position, and then add a single sync point to EQMOD.
The part about adjusting polar alignment after slewing between star pairs is what some of the software-assisted approaches such as AlignMaster and the SynScan handset do. However, they also separate out the alt vs az components of the error so you can adjust the mount more precisely (arc secs at a time).
I'm not sure how generally true this is, but I've personally found that if I start with a horizontally level mount/tripod, and slew between star pairs so that they are as far apart as possible (i.e. one star lowish on the horizon, the other high near the zenith) but on the same pier side, my PA reliably converges below 30'' in both alt/az within three iterations.
More advanced methods such as those used by PoleAlignMax and MaxPoint use plate solving of multiple points in the sky to calculate an average PA error, i.e. it takes into account flex in the mount. I've found AlignMaster more reliable for me than MaxPoint on my EQ6.