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OnStep alignment, does polar alignment accuracy matter? 2 or 3 stars?

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#1 ppg677

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Posted 14 August 2020 - 08:34 PM

Newbie with an OnStep build.

Do I need an accurate polar alignment for accurate GoTo? Can I just center polaris in the viewfinder if I'm not doing long-exposure photography? Or does it impact GoTo accuracy?

Alignment: 2- or 3-star good enough?

So far I've only tried 2-star alignment and GoTo is not that accurate. But I suspect I have backlash issues and I'm unsure if polar alignment matters for Go-to.

#2 rgsalinger

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Posted 14 August 2020 - 09:01 PM

If you centered Polaris in the viewfinder you would be 40 arc minutes (roughly) off the pole. Not good enough if you want to take long exposures, in general. If you can get within 5 arc minutes then you are in business most of the time. 



#3 hjd1964

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Posted 16 August 2020 - 07:41 AM

As for polar alignment and goto accuracy having less error to correct is better, but generally speaking it's not that important to be exactly on the pole.

 

For alignment three or more stars is best, all should be somewhat away from the NCP/SCP and also well spread out.  For a GEM make sure at-least one star involves a meridian flip.


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