How to stack with Ha, Hb + Oiii

Hi, I am considering purchasing the Optolong L-enhance filter which isolates the Ha, Hb & Oiii. If I capture using this how can I integrate with the normal luminence image? I have seen the option to add Ha with the R but as this filter is collecting 3 different frequencies how do I combine?

Hi, H-beta and O-III are very close and will not be differentiated in the output. Siril can process these images by extracting the H-alpha from the red filter and the other lines from the green and blue filters.
After processing you obtain two monochrome images that contain for one the H-alpha and for the other the combination of H-beta and O-III.

Recombining this to a colour image involves RGB or LRGB composition, as documented here: Siril - RGB composition

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I dont have any other filters. My understanding is Ha, Hb will be almost reddish and Oiii will be teal colour and hence my doubt. As this particular filter will isolate both colours at one go.
If I had individual filters then I understand the process from your tutorial :slight_smile:

Hb is towards blue, with wavelength close to OIII.

It seems there is some confusion here about how the filter works. The filter allows light to pass through only in 2 relatively narrow bandwidths. When the light reaches the OSC, the Ha is registered mainly on the R pixel, and the OIII+Hb mainly on the G and B pixels. The OIII and Hb come together as a “package” and cannot be separated. That is by nature of the OSC.

The best approximation for separate emission lines is therefore to assume all the red pixels are only Ha and the G and B are only OIII. That is what the siril command extract HaOIII does.

One image gets split into two - one from all the red pixels which is assumed to be Ha and one the average of green and blue, which is assumed to be OIII. these can then be treated as though they are from an Ha and OIII plus mono capture. Note this will continue to be an approximation.

So the final combination can only be of Ha and OIII. Eg HOO is possible, SHO is not.

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Perfect. Didnt know about the command HaOiii. That should solve my problem :slight_smile: