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INDI Library v1.9.5 Released (08 Mar 2022)

Bi-monthly INDI Library released with new drivers and bug fixes.

Some questions about the polar alignment function

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Hi all.
I had an opportunity the other night to try out the polar alignment function in Ekos and I have a couple of questions.
Overall the procedure worked fine, It solved the image, re-located and solved again and calculated the error (for both Az and Dec)
But when selecting the "Correct Az Error" (for az ajustment) It was hard for me to know what star I was supposed to center in my FOV. Does the module just select a nearby star that's close or does it select a star that stands out a little bit (a brighter star)? I could not single out a star that was a good candidate for centering.
I was however able to correct the aligment error by adjustning blindly and then doing another measurement of the error until it was within tolerance.

Also does Ekos when displaying the error (too far east och west for Az) account for how the image is oriented? A refractor and reflector give different orientation (backwards, upside down etc.) I'm not 100% sure but I think when it said too much to the east, I adjusted west, but then the east error grew instead. Adjusting to the east reduced the error. But as I said, not 100% sure I did this right. I was very tired at the time :)

/Daniel
7 years 4 months ago #2545

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I updated the Polar Alignment workflow documentation a few days ago, please take a look at it. Regarding the orientation, you're right, I only considered my refractor. I guess I can figure it out from the image orientation, let me test that.
Jasem Mutlaq
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7 years 4 months ago #2546

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Thank you, I will look into the updated documentation.
Also I forgot to mention that I used a Newtonian when testing this.

/Daniel
7 years 4 months ago #2547

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Ok, can you tell me what is the rotation angle you get when you solve images in your current setup? It shouldn't matter but I wanted to make sure of one thing.
Jasem Mutlaq
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7 years 4 months ago #2587

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Hi. I resolved an image from the session on nova.astrometry.net (I don't have the gear setup just now so I can't use ekos), and it gave the following response regarding the rotation angle:

This was not however with an image used when doing the polar alignment, but hopefully it doesn't matter?
/Daniel
7 years 4 months ago #2594

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It shouldn't. One more thing, you use the _right_ azimuth knob to the move the mount westward, correct? I'm also assuming you live in the northern hemisphere.
Jasem Mutlaq
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7 years 4 months ago #2597

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Hi. I'm not really sure but If i'm standing behind the mount facing north and adjusting the right knob, I think it moves the mount eastward. But the view in my telescope would be moving westward because of the orientation of the view, or am I wrong?
I have a Sky Watcher NEQ6 Pro SynScan mount.

And yes, I live in the northern hemisphere.
Last edit: 7 years 4 months ago by Daniel Franzén.
7 years 4 months ago #2602

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I believe it moves westward when adjusting the right knob. When the weather clears, I will make one more test, but I confirmed that the orientation is irrelevant to the final azimuth correction, i.e. it doesn't matter what optical system you use.
Jasem Mutlaq
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7 years 4 months ago #2605

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Hi again.
I did another test session with the polar alignment and I was following the steps from the polar alignment workflow.

I have a question though, when finishing one iteration, if I want to redo the measurement do I have to include the step where I capture and solve in GoTo mode or can I just click the "Measure Az/Dec error" again?

I got some weird result when adjusting Dec error after the first iteration. The initial error was about 1 degree and after doing a small adjustment to the mount I just clicked the measure Dec error button again and after it captured and resolved it reported an error of 111 degrees, which I don't think is correct :)

/Daniel
7 years 4 months ago #2644

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No need to switch mode to recalcuate. And yes, sometimes it gives bogus results, I think I'll have to put limits in the algorithm and retry again. I was suppose to test it today but didn't have time, will give it a go tomorrow.
Jasem Mutlaq
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7 years 4 months ago #2646

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Ok so you were correct! right knob moves east, I updated Ekos it should give correct results now and I will update tutorial as well.
Jasem Mutlaq
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7 years 4 months ago #2653

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Hi, I tested the polar alignment feature again last week and when calibrating Dec Ekos said my mount was too high, so I lowered it a bit and then I got an even higher error. When instead adjusting the mount higher the error decreased. So do you think the shown error is also flipped like Az was?

/Daniel
7 years 1 month ago #3618

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