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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

Polar alignment non-goto mount

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Replied by Phil on topic Polar alignment non-goto mount

I have a SkyGuider Pro and I too would like to see a non-critical placement manual adjustment in Ekos, so you can manually rotate to roughly 30° positions and the program triangulates from there. PHD2 needs a better alignment tool as well. I do not find the concept of regular drift alignment remotely attractive, and I would like to see a more accurate Polar Drift Alignment tool in PHD2, essentially one go to, one-shot alignment procedure. Having to jump to multiple alignment routines in PHD2 seems unnecessary.
3 years 9 months ago #55926

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The current three image PA method in Ekos doesn't need critical movement of the mount, just that the movement is large enough that there is a signficant change to the images. Any movement over about 15 degrees should be enough. There must be no movement of the dec axis, that's not difficult to achieve.

The only one goto, one shot polar alignment I know of is Celestron's ASPA and this uses the previously done mount alignment to get the polar alignment error.

The nature of drift alignment means that it can only see the error in one direction so it hs to be done in two positions.

Part of the problem with polar alignment is that people are too fussy. A small amount of PA error can be guided out and may help because the declination corrections are all in the same direction. What is left is field rotation and if you do the sums this will be insignificant.

A PA error of less than 10 arc minutes should be fine. If you have a permament mount then it may be worth the effort to get closer but even then less than an arc minute won't achieve anything useful.
3 years 9 months ago #55930

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Polar Drift Alignment is close to being one-shot. It operates near the pole and relies on the fact that PA drift is perpendicular to the PA error so it detects the error on both axes. It also does not need any calibration for camera rotation nor any slewing. All it needs is a guide star within about 5 degrees of the pole. On the down side its accuracy is limited by PE and seeing as it uses very small drift amounts that get smaller as PA error reduces. It can also give wrong results when tracking is disabled as the resulting RA drift is indistinguishable from PA drift. But used correctly, it should however be able to get within 10 arcminutes quite readily and in good conditions even less.
The theory is described at canburytech.net/DriftAlign/DriftAlign_4.html
I developed the module in PHD2 so it would not be a stretch to implement in Ekos.
3 years 9 months ago #55933

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Replied by Phil on topic Polar alignment non-goto mount

Thanks for your replies. I was under the impression that PHD2's polar drift alignment was not accurate enough. The videos I've seen on it seem to dictate to run additional polar alignment like static or drift. If polar drift alignment is accurate enough, that's good enough for me. :)

The same goes for the Ekos polar alignment. I was under the impression that you had to be exactly 30° apart in order to get proper data for alignment, but if just rotating to approximate 30° positions is adequate for proper alignment then I'm good to go with that. Is there a provision in Ekos to manually rotate?

Thanks again for your replies.
3 years 9 months ago #55948

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I see a "Manually Slew" option when I use the mount simulator:




Wouter
The following user(s) said Thank You: Phil
3 years 9 months ago #55952
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Replied by Phil on topic Polar alignment non-goto mount

Hello, it's been a while since I used the Astroberry setup, and I recently updated Astroberry which has KStars 3.5.2, and I can't find this panel to manually slew the polar alignment tool in EKOS. Where can I find it so I can use it with my SkyGuider Pro?

Thanks for any info on this.
2 years 9 months ago #71847

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Replied by Phil on topic Polar alignment non-goto mount

...never mind, found it.
2 years 9 months ago #71941

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