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PPEC and guiding concern

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4 replies to this topic

#1 MakNewtMan

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Posted 28 February 2020 - 09:39 AM

I can’t seem t find a clear answer on this. Little back info on my setup: EQ6R-Pro mount and OAG for autoguiding. I can t seem to get better than about .8 Total RMS with my 8” RC using a Celestron OAG and QHY5iii 174M camera. I want to improve my guiding but am not sure what the best solution is.

My initial thought was to PPEC train by mount. Then Auto guide along with the PPEC trained mount. However, I read just as many people saying that the PPEC hurts auto guiding just as much as it can help auto guiding. Does anyone out there have experience with PPEC training and EQ6 R pro mount and then also auto guiding? if so, what are the results? improved or not? I believe my mount suffers from a fairly strong periodic error and therefore limits my guiding capabilities. Should I just stick to auto guiding or will I see a true benefit and PPEC training my mount in addition to auto guiding?

#2 Kevin_A

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Posted 28 February 2020 - 09:47 AM

Personally i initially set up PPEC training while guiding once when i got the mount.... then use it only when I am not using a laptop and guide scope...... 



#3 MakNewtMan

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Posted 28 February 2020 - 09:59 AM

I’m assuming you have the same mount. What are your Total RMS numbers on PHD?

#4 jerahian

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Posted 28 February 2020 - 10:39 AM

I’m assuming you have the same mount. What are your Total RMS numbers on PHD?

I have the same mount, and my guiding numbers are generally around 0.7 total, but does get down to low 0.5s total for stable nights.

 

It is a fallacy that PPEC and auto-guiding fight each other.  Auto-guiding will correct for any PEM you may have, and all a good PPEC does is reduce the amount auto-guiding has to correct.  Personally, I used PECPrep to capture and process my PHD2 guide logs once.  Then I load it once in EQMOD and since then, once it starts tracking, it tracks "Sidereal+PEC".

 

That said, I saw no difference before and after, and as I mentioned above, that is because auto-guiding largely corrects for all your PEM anyway.

 

The biggest 2 factors I've noticed to impact my guiding are:

  1. Seeing
  2. Wind

Really, that's largely it.  Of course, one can screw up the PHD2 configuration settings to really jack it up, but the defaults are usually pretty good for the most part.  On my EQ6-R Pro, I generally use 1.5 to 3s exposures.  Basically, if I can, I set my PHD2 configs to minimize the corrections which have to be made if the mount is tracking well for the night.

 

GL&CS!


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#5 MakNewtMan

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Posted 28 February 2020 - 11:25 AM

Thanks Jerahian. My seeing conditions were average according to the forecast so I expected a bit better with guiding. I suppose .8 isn’t bad but really depends on your image scale and mine with my RC and Canon 77D is .46. I fear I’m losing some resolution due to the mount not tracking better than .46. This just may be a limitation of my mount but I’ll do more research on the PHD settings. I will say, that for my mount, the default pulse settings are far too slow/weak for my setup. I have to bump those numbers up to 2500ms. Anywho, thanks for chiming in.
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