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

Bi-monthly release with minor bug fixes and improvements

Auto Focus - OSC dual-narrow band filters issue

  • Posts: 910
  • Thank you received: 86
Hello,
I asked about this at a Cloudy Night forum and got some useful answers.
I am wondering if this could be improved some more...

Problem: Red channel is focused perfectly, Green and Blue are out of focus.
That's when FITS Auto Debayer is turned ON.
I believe, in this case Ekos is using the Red channel to focus on.

When Auto Debayer is turned OFF, the focusing is better but the Red channel is slightly out of focus.
Better but not perfect.
I believe, in this case Ekos is using the average grey level image to focus on.

Is there anything which currently could be done to focus all channels more equally?

Thanks!

Example. Debayer is ON. Antlia ALP-T (L-Ultimate is similar).
Red vs Blue.


Example. Debayer is OFF. Antlia ALP-T.
Red vs Blue.
-- Max S
ZWO AM5. RST-135. AZ-GTI. HEQ5. iOptron SkyTracker.
TPO RC6. FRA400. Rokinon 135 and other lenses.
ZWO ASI2600MC. D5500 modified with UVIR clip-in filter.
ZWO ASI120MM Mini x 2. ZWO 30F4 guider. Orion 50mm guider.
ZWO EAF x 2.
Last edit: 1 year 2 months ago by maxthebuilder.
1 year 2 months ago #89836
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Hi maxthebuilder,

I haven't looked into this but just thinking out loud...

If you are debayering then Ekos is *probably* taking the first channel. Just looking at your signature if you are using the ASI2600MC Pro then the bayer pattern (according to google) is RGGB. If you don't debayer then it may be using data from all channels? - not sure, have to look into it.

Could potentially allow a configuration to let focus use data from a user specified channel so if you want better focused Ha or Sii then choose Red (but the Oiii will be out of focus). If you want better focused Oiii then choose Blue (but the Ha/Sii will be out of focus).

The only way to get everything in focus at the same time is to have a "tool" to make the optical path through the telescope, filter and camera par-focal so when Ha is in focus so is Oiii.

Alternatively in post-processing, something like BlurXTerminator will deal with the colour fringing around stars (but can't completely compensate for some of the data being out of focus).

Will think some more about this...
1 year 2 months ago #89853

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  • Posts: 910
  • Thank you received: 86
Jon,
Yes I had same ideas.
When auto debayer is off the focuser seems to use averaged grayscale histogram with acceptable results.
BlurXT sure helps.

Thanks!
-- Max S
ZWO AM5. RST-135. AZ-GTI. HEQ5. iOptron SkyTracker.
TPO RC6. FRA400. Rokinon 135 and other lenses.
ZWO ASI2600MC. D5500 modified with UVIR clip-in filter.
ZWO ASI120MM Mini x 2. ZWO 30F4 guider. Orion 50mm guider.
ZWO EAF x 2.
1 year 2 months ago #89878

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