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How do I replace the Red Channel in an LRGB image with a new Red Channel

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Hi, I have spent hours trying to do this can anyone help?

Basically I have an LRGB image of the Andromeda Galaxy but want to add in some HA (additional Red) data.

I have taken a copy of the original Red data from the LRGB and blended in the new HA data and now want to put this RED-HA data back into the LRGB Red channel, replacing the original Red data.

I suspect I need to create a spare channel, add the RED-HA to this and then Load the Spare channel into the Background Red.

If so, the bit I cant work out is how to put the RED-HA into the Spare channel.






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Take a look at the Channel Tutorial videos (especially the Channel Packing one) and this "Learning Channels" article from @James Ritson :


☛ Affinity Designer 1.8.3 ◆ Affinity Photo 1.8.3 ◆ OSX El Capitan

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Thanks, I worked it out.

For anyone else wanting to merge HA data into an LRGB image this is how I did it.

I had already fully processed my LRGB and Ha images before doing this. 

Create new Ha-Red file.


Open LRGB and Ha Images in AF


Open the LRGB Image

Select LRGB Pixel Layer

Right-Click LRGB Red Channel>Create Greyscale Layer.

Select Greyscale Layer and Copy


Open the Ha Image

Paste Greyscale layer onto Ha Image and rename layer as Red.

(Delete the Greyscale layer from the LRGB Image - no longer required).


Adjust the Red Opacity to around 25-30% and Save. (Need to experiment with opacity).


Copy the Ha layer (which now also includes Red).


Add Ha-Red to LRGB

Open the LRGB image and paste the Ha-Red layer as a new pixel Layer and label as Ha-Red.


Highlight the Ha-Red layer.


Select>Save Selection>as Spare Channel


Highlight the LRGB layer.

Right Click the Spare Channel and Load to the LRGB Red channel.

Use the Channel Mixer to get the balance right then process as required. I used the following Denoise approach which worked well.



Applying Denoise to each channel separately seemed to work well:

Highlight the LRGB Pixel Layer

Click Composite Red - can now see noise in Red layer

Layer>New Live Filter Layer>Denoise

Experiment with luminance and colour denoise - use as little as is necessary.


Repeat for other channels.

The colours are not right so I need to reprocess but the addition of the Ha has worked well - see image.



M31 Ha LRGB v3 1024.jpg

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