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Calibration failed : star drift is too short

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Hello all,
Last night was a nice clear night even with the moon. So I decided to test my setup that is now fully functional.
(AZ-EQ6 + guider ZWO 120 on Lumicon 50mm finder + SBIG 8300C + self made moonlite like focuser + INDI server on Odroid XU4 + TP-LINK TN722N for wifi connection)
I made a focusing sequence to get the best focusing. I got a 1,7 HFR. I was really happy my focuser works fine.
I decided to improve my polar alignment with astrometry. Go south and adjust blindly the AZ position ==> 8". Go west and adjust blindly the ALT position ==>5".
Once more I was happy of the result. All woks fine.
Moving to Capella and made some plate solving to center the star. After some gropings got the sync on the star.
Was late and I ask the mount to go to Vega. Then others plate solving with sync.
Moving to M57. The nebula went to the center of the field. Nice !
Waiting some minutes doing some plate solving to see if there is some drift. No more than very few seconds.

Now Imaging.
First mount calibration. I was confident.
Took a capture and the automatic process does work with finally "Calibration failed : star drift too short".
Well maybe the focus is too good on the finder. I de-focused a little bit.
Choose the same star and ... "Calibration failed".
Mmmm maybe a little problem of... I don't know. Let's have a new try.
Choose another star and ... "Calibration failed"
Whatever I decide to guide without calibration. All went good at the beginning but got a big drift after a minute or two.
I am not so confident now I think that the poor debit between the Odroid to the PC may be a problem.
I choose quick guiding (on odroid).
Better result the drift grows slower but grows. So I find that a poor connection is one od the problems.
Back to the calibration with same last choosed star ==> "Calibration complete".
:blink: lets try once more ==> "Calibration failed".
Trying some parameter adjustment on the pulse duration. Nothing gives good result.
Testing the balance of my setup. It is good.
Took some pics of 60s max to avoid drift without calibration and rapid guiding. Stars are round and pretty.

My first conclusion is that the poor connection might be the source of my problem.
But I am not a confirmed user to put a definitive diagnostic. So I am very open to your suggestions.
I will try with PHD2 next time but I have to learn to know how to connect PHD2 and Kstars/Ekos on same INDI server.

Clear skies
7 years 11 months ago #7841

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Read those Tips for Better Guiding

Was guiding via ST4 or what?

Also, turn on verbose logging in KStars options and attach your kstars.log file. This is the only way to diagnose any issues with the guiding process.
7 years 11 months ago #7842

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No this is not via ST4 it is a via EQMOD link.
I will do it I only have to wait for clear nights.
I will also try to combine PHD2 and Kstars/Ekos to see if the problem still persist.
I have another problem but don't know if this is the good place to evoke it: when I load the tifs pics from ekos in pixinsight I only have one gray channel.
Last edit: 7 years 11 months ago by Patrick.
7 years 11 months ago #7846

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Hi!

Just a few thoughts to play with (turning on verbose and diagnosing is the best way):
I had similar problems with calibration before (using Ekos internal guiding module) - solved by increasing the step size. Same issue in PHD2, by the way, so now I always use rather large step sizes, and calibration almost never fails. But my mount is a Losmandy G-11, different from yours.

I'd also try switching from guding via camera, and via Indi.

Magnus
7 years 11 months ago #7877

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Hello Magnus,

Can you tell me what values did you used as time step ?
I tried a lot increasing and decreasing the values from 100ms to 2000ms but got very variables results and 90% time failed.
A set of your parameters could help me.
I hope I will be able to test it before end of month. Unfortunately the weather is so unstable :( .

Patrick
7 years 11 months ago #7878

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Hi!

I have the stepsize at 2000 ms now, but I have mostly used PHD2 lately, where I have even larger stepsize (up to 4000), to avoid calibration failures even when calibrating in high declinations. I often get warnings (axes moving unequal amounts etc) that I believe have to do with backlash in my mount (a later project).

How's the calibration with PHD2, just for a comparison? Does that fail too?

Magnus
7 years 11 months ago #7880

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Hi again,
Didn't try with PHD2 yet. It is in my projects for my next sessions if the weather turn well.

Clear skies (I hope)

Patrick
7 years 11 months ago #7881

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Hello
@Jasem
I tried yersterday to calibrate my mount with ekos. It works once but failed at the second try.
I activate verbose option of kstars and produce a log when failed. But, unfortunately, to know where the log was stored I run kstars this morning with the result of deleting the previous log file. Would it be possible to keep several versions of the logfile with a control on the deepest number of versions ?

Otherwise, in the same situation (same target), I succeeded to calibrate the mount with phd2. But as I don't know what are the relation of phd2 parameters and ekos parameters I don't know what can be the good parameters for ekos.
7 years 10 months ago #8527

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Did you set binning 2x2? For PHD2, there are no "parameters". Just get PHD2 to guide and that's it.
7 years 10 months ago #8528

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Ok I misunderstood the parameters part. Read the FAQ about guiding tips for calibration
7 years 10 months ago #8529

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