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Relationship between seeing quality and PEC quality ?

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#1 ChrisMoses

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Posted 14 August 2022 - 02:06 AM

Hi,

It makes sense that fairly good seeing is required to get a good PEC run, but, a few questions:

 

  • How good of seeing is good enough?
  • Is there a relationship between seeing quality and PEC quality?

 

I generally measure seeing first on the 1-5 scale of ClearDarkSkies and just started trying to use Sharpcap to get a more instantaneous measurement.

 

Does anybody have any quantitative or qualitative insights?

 

Thanks,

Chris



#2 Drothgeb

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Posted 14 August 2022 - 07:03 AM

How good is good enough, depends on your pixel scale. Guiding at your pixel scale will give you decent results, but I usually try for half my pixel scale and take what I can get.

 

When I have my ASI294 on the 390mm Hyperstar, pixel scale is around 2.5”/pixel. Guiding is easy with average 2-3”  seeing, I’ll usually see 0.6 - 0.8” rms. When I have the ASI2600 on the 1500mm setup, pixel scale is more like 0.5”/pixel. Then, I’m hoping for 1.5” seeing or better. Then I’ll usually see 0.3 - 0.5” rms.



#3 StephenW

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Posted 14 August 2022 - 09:42 AM

The benefit of a tool like PemPro is that it averages the recorded PE over multiple worm cycles.  I generally let it run for at least 10 cycles.  As a result, it is able to extract the PE error from the seeing noise. 

 

That said, I probably wouldn't bother do a PEC run unless the seeing was 3 or higher.   



#4 Jared

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Posted 14 August 2022 - 10:17 PM

Hi,

It makes sense that fairly good seeing is required to get a good PEC run, but, a few questions:

 

  • How good of seeing is good enough?
  • Is there a relationship between seeing quality and PEC quality?

 

I generally measure seeing first on the 1-5 scale of ClearDarkSkies and just started trying to use Sharpcap to get a more instantaneous measurement.

 

Does anybody have any quantitative or qualitative insights?

 

Thanks,

Chris

As Stephen mentioned, multiple worm cycles will ensure you get a good result even with mediocre seeing. With five or more full worm cycles you should be OK even with average seeing--perhaps my standards were not quite as high as Stephen's. That should be enough to minimize the work for your guider.


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