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APP Ha OIII extraction from OSC with Duoband filter - Unmixing Bayer colour leakage from duo band filters  

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(@djibi)
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Joined: 1 year ago
Posts: 1
April 26, 2021 21:28  
Posted by: @mabula-admin

If you debayer with Ha-O3 color and the split the channels of the RGB result, the red channel is the H-alpha signal, and the green and blue combined is the O3 signal. APP makes it easy, with the extract algorithms, to immediately provide you with these monochrome Ha & O3 signals without loss of resolution which has great benefits of course.

Let me know if this clarifies things

Hello Mabula

Recently, I have been a lot of testing to check the difference on the Oiii results after an OSC capture with dual narrow band filter, an Idas NBZ in my case.

Even if the Green channel is the main "input channel" for the Oiii wavelength, there is still some SNR improvement to get from the blue channel.

So I tried and compare the 4 following channels from the exact same set of datas:

- the Green channel obtained after the "Ha-Oiii colour" algorithm

- the Blue channel obtained after the "Ha-Oiii colour" algorithm

- the Oiii obtained after the "Ha_Oiii extract Oiii" algorithm

- the B_G obtained after an integration of Blue and Green channels with a ponderation based on quality (the 2 channel are linear fitted before the action) 

 

Here is waht I saw from these :

1- the worst SNR is the blue channel, 

2- then Green channel, Green has a better SNR than blue

3- B_G is better than Green (and blue obviously) , 

4- Oiii is better than Green 

5- not a big difference but I would say that B_G is slightly better than Oiii in terms of SNR; always hard to compare, you have to make a strict comparison of the histogram and evaluate the "width of the sky background" for example and be sure that there are no offset that disturbs the analysis, and if there is a difference, in all cases, it is a very very small difference

 

So my question to understand the "Ha-Oiii colour" compared to "Ha-Oii extract Oiii" algorithm :

- why Green & Blue are differents with "Ha-Oiii colour" ? after all, we want to get 2 channels : Oiii & Halpha, why leaving the Green and Blue "separated" ? Obviously the blue capture from the camera has a worse SNR that the green but why leaving thes channels in the Ha-Oiii colour algotithm ?

- Am i correct in the analysis of Green / Blue channels versus Oiii ? If yes; why didn't you provide an algorithm that provides the results of Halpha and Oiii in an HOO RGB file ?

 

I hope that I am clear, I am a little disturbed because what you implemented seems the best way to extract a dual narrowband acquisition but still, two operations needs to be done : either play the datas with "Ha_Oiii extract Oiii" then "Ha_Oiii extract Halpha" algorithm or play the data with "Ha_Oiii colour" then recombined Green and Blue channels

 

thanks in advance ... and thansk for your work 🙂

 

Jean-Baptiste 

(from France)

 


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