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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 problems, maybe.

  • Posts: 194
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Hi,

I used the legacy polar alignment method in Ekos for the first time to align my LX600. It felt like everything went Ok. I have 24 seconds east and 39 seconds low on the readouts. But when I drift at the meridian and equator, the field drops probably 5 arcseconds every minute. I figured that could be one of two things - Ekos is not accurate enough or 24 seconds and 39 seconds are not as good as I thought they were. I've never measured the error before - I just drifted until I got it right. Any opinions are welcome!

Thanks,
Dave
3 years 6 months ago #59887

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I am relatively new to astrophotography and EKOS and mainly use the standard PA assistant so I will help the best I can and hopefuly somebody wuth more experience will jump in.

In my experience, an error of half an arcmin should be decent for up to 30secs or even 1min unguided subs.

Considering that the earth spins at 15 arcsecs per sec at the celestial equator, so having a drift of 0.08 arcsecs per sec (5arcsec per min) seems very decent!

I use a 600mm SW 80ED with a ZWO 1600, that combination results in ~1.3arcsecs per pixel. If you are having 5arcsecs per min drift would mean that for a 1min sub , there would be a 4 pixels drift. For an unguided setup, I think I can live with that. If you cant, then indeed that PA error needs to be reduced.

The bigger problem is that for a long imaging session, the drift would cause issues with the composition. Using the same maths, after 1 hour, I would be 230pixels off... The only solution I can see to do is either further improve PA accuracy, do plate solving every now and then or use guiding.

Regards
OS: Astroberry on Raspberry Pi 4 4GB
Mounts: EQ6R-Pro, StarAdventurer
Imaging: SW Evostar 80ED & SW 200PDS, ZWO ASI 1600MM-PRO
Guiding: SvBony 60mm, ZWO ASI 120MCS
Accesories: ZWO EFW, ZWO EAF, Pegasus PPBA
Last edit: 3 years 6 months ago by Raul.
3 years 6 months ago #60219

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Thank you for the detailed answer.

I went out tonight and polar aligned using the legacy tool in Ekos, and it said my final was 54" out in azimuth and 12" out in altitude. Objects don't drift at all in the field of view, and I can make 3 minute exposures without having to throw half of them away. Now I have to figure out how to get everyone to turn off their lights. I have a Bortle 8-9 in my location.

Thanks again,
Dave
3 years 6 months ago #60224

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Glad it works! I do have usually less than half an arcminute error but I do see a drift when I replay my subs in Pixinsight from my imaging sessions and its evident when i stack them in DeepSkyStacker.
I am confident that in my case, it will be solved with guiding so I am not worried.
OS: Astroberry on Raspberry Pi 4 4GB
Mounts: EQ6R-Pro, StarAdventurer
Imaging: SW Evostar 80ED & SW 200PDS, ZWO ASI 1600MM-PRO
Guiding: SvBony 60mm, ZWO ASI 120MCS
Accesories: ZWO EFW, ZWO EAF, Pegasus PPBA
3 years 6 months ago #60225

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