What is the blue channel in Ha-OIII Color?

Posted by: @digitaliz-se

How is the blue channel composed when using Ha-OIII Color.
The algorithm Ha-OIII Color and the Airy Disc are almost identical if you compare the end result.

Both the blue and green channel contain OIII data. The exact amount depends on the filter used and the sensitivity of the green and blue pixels to the passband of the filter. The difference between the two is that choosing Ha-OIII Color makes APP split the Ha and OIII channels (by combining the G and B channels into OIII), process the data and then split up again. This will result in slightly lower noise when compared to Airy Disc.

Posted by: @digitaliz-se

I am asking since I wish to use the data in the blue channel, then composing in the RGB Combine tool.
Extracting Ha, OIII and then redoing the stack for Ha-OIII Color just to get the blue channel is cumbersome.

This is the only way to separate Ha and OIII in APP. In a future version it will be possible to split Ha and OIII in one go. You can extract the G and B channels and combine them into a single OIII mono image yourself in external image processing software if you prefer.

HTH, Wouter

Ok, 

Thanks!

/Stefan