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Polar alignment with a polar scope
The use of a polar scope is not a beginners way to polar align a telescope. I have tried it and identifying sigma octans in a small polar scope is not very easy unless you are very familiar with it. You need to get the hour angle correct and the elevation and azimuth within 1 degree to have a reasonable chance of making initial identification. The precision that can be obtained is not good enough for long exposures. Another problem with polar scopes that is that in a period of 20 years the South celestial pole has moved 6 arc minutes. How old is your mask.
Orthogonality and Stability
Orthogonality is the biggest problem with polar alignment. Using a standard GEM you need to rely on maching accuracy as there is no direct adjustment. Next is the stability (rigidity) of the mount.
Drift alignment
Drift alignment is the way to get fine and accurate polar alignment but it must be complete with alignment at the horizon as well as at the zenith. This was once very time consuming but now with auto guiding programs this can be reduced to a few mniutes.
Barry
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