The Dwarf mini has a dual-band filter that effectively separates the O3 into the green and blue channels and the H-alpha into the red channel of the colour image it produces.
We are going to take the 16 bit PNG produced by Stellar Studio and re-process it into a real HOO image. The image we shall use is a mosaic image of NGC7000, the North America Nebula.
We shall convert:
RGB
and convert it into:
HOO
Let us look at one method of doing this:
Click on any image to see it much closer
We shall use GIMP in the main.
There are various ways of doing this. The first thing to do is to save the 16 bit PNG as a 16 bit TIFF. The reason for doing this is that some software only treats PNG files as 8 bit files and converts them after reading them. We want to retain the 16 bits until the very end of the processing.
We shall start with a starless version of the original image plus the stars image. These could have been obtained from the original image in a number of programs so for that part we shall not be prescriptive.
Starless RGB image
We have to split the RGB image into it's three monochrome channels; R,G and B.
Colours
Components
Decompose (NOT to Layers; Colour model RGB)
Three monochrome images will appear:
Red channel: H-alpha, H
Green channel: O3
Blue channel: O3
We next have to combine the Green and Blue channels as they contain the O3 data.
Select the Green channel (the middle one at the top).
Edit
Copy Visible
Select the Blue Channel (the right hand channe at the top
Edit
Paste as
Single layer (depending on the version of the Gimp you are using, it might say New layer)
At the right hand side, select Mode Addition.
Then:
Image
Flatten image
This has created the O3 monochrome image.
Then delete the Green channel as it is no longer needed.
You might then need to use levels to bring up the brightness of the new O3 image to a level similar to that of the H image.
The adjustments can be seen in the Levels dialogue in the screenshot below.
Note that is has not just been made brighter, but the dark areas have been preserved by bringing in the left hand slider a little.
This process of making the H and O3 images of similar brightness distributions is called normalisation.
The H and O3 monochrome images now have to be combined into an HOO false colour image.
The H is placed in the Red channel and the O3 is placed in both the Green and Blue channels of the colour image that will be created.
Colours
Components
Compose
A dialogue like the one in the screenshot below will appear.
Take your time and make sure that you assign red to red
blue to green and blue to blue
When you click on OK the HOO image will be created.
Save the image with a sensible name like: NANEB_HOO.tif
At this stage it is still 16 bit.
Then load The HOO image into GraXpert
DON'T extract the background because this will already have been done by Stellar Studio right at the start.
Denoise the image.
When Denoising is complete:
Select Saving
Set to 16 bit Tiff
Click on Save Processed:
GraXpert will give a new filename by adding Graxpert to the end of it
The name we can see that has been generated is NANEB_HOO_GraXpert.tiff
Click on Save

You can then load this image into GIMP
If you need to, you can select:
Colours
Hue-Saturation
and increase the Saturation a LITTLE as shown in the dialogue in the screenshot below
Then load the Stars image into GIMP
Select the Stars image
Edit
Copy Visible
Select the HOO image
Edit
Paste as
Single layer (or New layer in a different version of GIMP)
On the right hand side
Select Mode Screen
This will screen the stars back into the image.
Export the image as NANEB_HOO_starsback.tif
If you then Export the image as NANEB_HOO_starsback.jpg
It's bit depth will be reduced to 8 bits as a JPG image suitable for sharing.
The original image and the HOO image animation
