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EQ6-R pro Ra guiding issue

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#1 Wei

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Posted 21 October 2020 - 12:09 AM

Hi,

 

I have a EQ6-R Pro that I am guiding using Asiair pro.

 

I couldn't figure out the issue with the RA guiding that is consistently lagging  behind by 1-2 arc sec. Is this lag cause by worm gear mesh?

 

Hope someone can shed some light on the issue.

Thanks.

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#2 sn2006gy

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Posted 21 October 2020 - 07:45 AM

I can only chuckle because with your lag, you're seeing/total RMS is better then what I get... ever... in my bortle8 skies.

 

Obvious question is, are you balanced  - center balanced? east heavy?  Does asair have some calibration you need to re-run after balancing?



#3 michael8554

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Posted 21 October 2020 - 11:26 AM

So long as the blue RA line remains at the same offset from the zero axis, RA results appear to be good, a relatively flat line comparable with the Dec line.

 

But curiously there are continuous blue RA corrections being applied that are having no affect on bring RA back to the zero axis.

 

When you start guiding, is the blue RA line on the zero axis, but soon moves off to the position shown ?

 

Does it ever come back to the zero line ?

 

Do you get a good Calibration of both RA and Dec ?

 

If not I'd suggest the RA corrections are not getting through to the mount.



#4 OhmEye

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Posted 21 October 2020 - 11:33 AM

I'm confused by the graph stats. The total RMS error for RA shows 0.30" yet the graph shows it must be much higher than that.



#5 Wei

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Posted 21 October 2020 - 12:55 PM

Screenshot_2020-10-20-21-22-45-054_com.zwoasi.asiair.jpg I typically get 0.45 to 0.8 total rms.  Just happens that the image I grab was the beginning section so it is a bit lower.

 

I tried to shift the counter weight to change the balance but no difference. I still get the lag.

 

The blue line usually never go past 0 when it starts the tracking, it does a turn about 1rms from 0 before it starts the actual guiding if you know what I mean.

 

Before the flip I get 0.45-0.6 rms error with scope point West.  After the flip with the scope pointing East, some times the tracking hits 0 intermittently but majority of it is still lagging with a higher rms error of 0.55 to 0.8.  I will try to get some screen shot tonight.

 

Frankly I can't complaint about the total rms as I it is sufficient from my usage.  Just don't know what is causing the RA lag. I guess it might be the worm gear mesh but I don't feel any play when I try to move the mount physically.


Edited by Wei, 21 October 2020 - 01:04 PM.


#6 OhmEye

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Posted 21 October 2020 - 02:08 PM

It just doesn't look self-consistent to me. That second screenshot says RA error is 0.39" but looking at the graph the RA is consistently much higher than that and obviously averaging higher than 1.0", it appears the average error is closer to 1.5", definitely not 0.39". It doesn't look like the RA line is even ever as low as 0.39" much less averaging that. The DEC error looks like it matches the graph but RA doesn't match at all.



#7 the Elf

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Posted 21 October 2020 - 02:49 PM

Theory 1:

Did you enter the guide cameras pixel size and the guide scopes focal length (including reducers or barlows)? In other words is the y axis correct? Could it be you are just below the min move or at the resolution limit and the translation from pixels to arcseconds is wrong? Not that it is impossible but the very small values point to a wrong scale factor imho.

Do you have PEC trained and active? If you watch over about 2 turns of the worm (20 min or so) you should see RA corrections in one way for a few minutes and the other one for a few minutes when PEC is off. In other words how the PE is corrected.

 

Theory 2:

How is your polar alignment? If RA is corrected in the same direction all the time your polar alignment is off. In that case you will never hit the zero line, that is how the control loop works. How much polar error does the mount report after 3 star alignment?


Edited by the Elf, 21 October 2020 - 02:54 PM.


#8 Huangdi

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Posted 21 October 2020 - 03:14 PM

It just doesn't look self-consistent to me. That second screenshot says RA error is 0.39" but looking at the graph the RA is consistently much higher than that and obviously averaging higher than 1.0", it appears the average error is closer to 1.5", definitely not 0.39". It doesn't look like the RA line is even ever as low as 0.39" much less averaging that. The DEC error looks like it matches the graph but RA doesn't match at all.



You seem to have misunderstood the graph. The graph looks at the movement of the star in the RA axis for a certain period of time. Once the right end of the graph has been reached, you have an average RMS error of that time period.

Now the important thing to note here, is that the 0 indicator (initial star center coordinate) is actually irrelevant for the RA performance.

So, whether the average error is 0.39" at center position or 2 pixels away from center position is irrelevant. The stars will be round. What changed is the entire field of view.


Anyway, I've had that issue before and usually it came down to software issues. One version of PHD2 worked nicely for me, the next one was utter chaos.

As you mentioned, gear mesh could be another issue. Lastly, I'd check balance. Try perfect balance, try East-heavy balance. Make sure you're not getting flexure. Re-tighten every screw on your setup. It's the small things...
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#9 the Elf

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Posted 22 October 2020 - 04:26 AM

My EQ6-R works well with perfect balance. IMHO the only figure that counts is the FWHM and eccentricity you have in the subs. If you try different guide settings or balance check the result in terms of FWHM in the subs. During my almost 4 year long journey I moved from 8 arcsecs FWHM unguided on an AVX down to 2.x off axis guided on the EQ6-R.



#10 Wei

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Posted 23 October 2020 - 12:29 AM

I think the lag was caused by connecting the asiair pro using usb cable to the SynScan handset.  Mount set as Skywatcher SynScan.

 

I switch the usb connection directly to the mount and selected Eqmod+skysafari as the mount and the lag has gone away.  Guiding average at 0.7rms error which is higher then what I get if I connect via the handset.

 

Does anyone have success connecting via the usb to the handset instead of the mount?  



#11 sn2006gy

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Posted 23 October 2020 - 01:48 PM

I sold my handset. Never gonna use it :)




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