Originally posted by k5astro: Electronic methods like pole master and Kstars appear to get very accurate alignment but I found that the results were questionable when I measured them using drift alignment measurements such as provided in PHD2.
This has troubled me somewhat. I always want to get to imaging so I never dwell on PA long enough to play around, but I think I probably should. The results from the polar scope in my CEM-25P do not agree very well with what I get from KStars' PA Assistant, and indeed if I rerun it I can't always get much closer results the second time. Drift alignment is of course the gold standard, since you're measuring what's
actually happening. I probably ought to at least run a "V-test", where you open the shutter, leave it dwell for awhile to develop a nice bright dot, slew in RA for enough time to make the star-streak encompass most of your sensor, and then slew back the same amount. That's about as close to definitive as it gets.
One of the issues with the CEM-25P is that the polar scope rotates with the RA axis, so "zero position" is absolutely critical. I have yet to have an imaging session where I could just use the last session's zero, there always is something that screws it up so I have to redo it. Am I careful? Yes. Am I getting it to within, say 10 seconds of arc each time? Heh. Let's not be silly.