Re: Notified!😍 #mach2gto #Mach2GTO

Terri Zittritsch

On Tue, Mar 10, 2020 at 02:44 PM, uncarollo2 <chris1011@...> wrote:
You should be able to get polar alignment good enough and keep it so with a solid tripod. Once aligned, I have not seen a tripod change the polar alignment.
Good polar alignment for imaging should result in Dec drift of 1 arc sec per 10 minutes at the meridian. If you also drift align the RA at the zenith, you should then also get 1 arc sec or better drift in 10 minutes for up to 2 hours on either side of the zenith. In PHD2 you can monitor your drift using the Trend Lines. You can then make tiny adjustments to the Alt and Az while watching the trend Lines and eventually zero in on perfect PA. Do the Azimuth first until the Dec line becomes flat - ignore the RA. Then tweak the Altitude until the RA line becomes flat. Do it on an overhead star. You might have to iterate a couple of times to get both Trend lines flat for at least 5 minutes. 
Thank you Rolando, I will give it a try next time I'm out.  You know, whenever I setup, I wonder just how stable things are.   My tripods by themselves are generally stable    But if for instance, a tripod foot settles 1mm, this can result in a 4 arc minute change in the polar pointing (referring to C. Woodhouse in the Astrophotography manual), I haven't done the calculations myself to validate this, but seems reasonable given the minuet changes required to get polar aligned (present incredibly poor accuracy aside).   Now that I've looked into it a bit, seems many people get amazingly good polar alignment results and not sure why mine is off so much (indicating as much as 5 minutes off the pole) when I am very careful in the process.     And just thinking about what it's doing, I'm not sure what could drive the inaccuracy except an incorrect refractive compensation.    In any case, some work for me to do.   Thanks again.

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