Re: How often do you need to polar align a permanent mount?


 

I just chatted with them just now, and they wanted to clarify they don't necessarily agree with a blanket statement "the more precise the PA the better"

Polar alignment error is only a problem when it creates image rotation and that’s pretty rare except for very wide field imaging.  That’s not really the same as saying “the more precise the PA the better” unless high accuracy just falls out from using PoleMaster or something. Or unless you’re trying to run unguided, in which case it matters a lot.

Brian

On Tue, Nov 3, 2020 at 7:51 PM Brian Valente via groups.io <bvalente=gmail.com@groups.io> wrote:
>>>" I have had one of the authors of PHD say that they prefer that the polar alignment is offset by like 8 arc-minutes.   Because if makes it easier to measure and compensate for a DEC polar error."


if you were experiencing significant dec backlash and their recommendation was to guide in only one direction, this offset PA advice makes sense. 


otherwise the more precise the PA the better for guiding. 


(I was a little surprised by this comment so i checked with the authors, and they confirmed my response)

On Tue, Nov 3, 2020 at 7:15 PM david w pearson via groups.io <p.davidw=yahoo.com@groups.io> wrote:
Not a clear cut answer to your question, as too many options that can be used to minimize polar alignment error affects.
I had a scope permanently mounted scope working at 1700mm with no encoders, but using PEC for 3 years and never had to realign after initially aligning to slightly less than 2 arc minutes
(Even had a small earthquake).
                  >Using PemPro or any other drift alignment process makes it fairly easy to achieve less than 2 arc-minutes.
But i could never do a 10 minute unguided exposure using Maxim DL, more like a max of 5 minutes.
I couldn't achieve 10min unguided until i did a pointing model with APCC.    And that doesn't last forever, meaning you have to periodically redo a model more than once a year.
i normally auto guide,  so I am not as sensitive to using an old pointing model, so that is the reason i don't update the pointing model very frequently.
I have had one of the authors of PHD say that they prefer that the polar alignment is offset by like 8 arc-minutes.   Because if makes it easier to measure and compensate for a DEC polar error.
Hope that helps
dave



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Brian 



Brian Valente



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Brian 



Brian Valente

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