I’m creating a real-world sized atmosphere with Geometry Nodes.
Based on this paper, I copied the scattering coefficients of Rayleigh, Mie and Ozone scattering and absorption.
There seems to be an issue though when using Ozone Absorption, the sky tends to look a little bit too red…
Here is the blend file (for 4.5)
Atmosphere.blend (1.2 MB)
It doesn’t look like a high red value to me. Maybe it’s your monitor settings?
The setup looks pretty accurate to me! Great work and thanks for sharing.
Colorwise, I guess it depends on what you’re comparing it to. Also the AgX version that is shipped with Blender has some hue shift in the reds – maybe that’s what’s throwing you off? Try filmic, this might be closer to what you’d expect.
Completely remade the atmosphere scattering and absorption, this time I followed the values and density distributions from this ShaderToy.
blend file for Blender 4.5:
Atmosphere.blend (1.1 MB)
Its good to see someone works on a “real” scattering sky.
I made some quick adjustments with the sun angle to see the sky colors at low angle.Til around 30 deg sun angle it looks ok,but if you go lower the light gets absorbed to much.Just guessing its absorption.From other sky models i have seen such darkening near 0 deg starting at maybe 4 deg
I loaded your first version and the light gets dark even earlyer with lower sun angle.around 80 deg.
what if you use a sun light for the volumetrics not the sky tex sun?
Ok thanks.
What about a haze layer for fog and wet weather etc? Most sky models have only this clear sky model.
Everyone can of course make a height based haze volumetric self.
But it would be nice to have a simple haze model integrated.
You maybe know the Terragen render ? They had even in the early versions a simple seperate haze control with great results to its time.
Would be nice to see such haze control in the sky model.
edit,I made a test with sun light only.I deactivated the sky tex and added a sunlight which i gave 1000 w and rotated to -87 deg.Adjusted exposure.
Now the interesting render,sun at -92 deg with plane active.
Nice scattering of the sky
Haze is simply the Mie scattering, you can multiply the “Mie Density” value to get more “haze” 
.
Atmosphere.blend (1.1 MB)
I’ve updated the atmosphere, now it has the Air, Aerosols and Ozone density multipliers.
This is great, can you share some images of the different settings?
Atmosphere.blend (1.0 MB)
Added a Sun lamp and added a limb darkening effect to it, this way it’s easier to control Sun direction instead of using the Sky Texture disc.
just to know…which Blender version is needed to use the blend file ?
Hello @marcatore 
4.5 is needed.
Tried with stable 4.5 but the sky is black… 
Are you sure you are using Blender 4.5 and not a previous version?
If I load the file loading also the UI I can see the sky.
If not, the sky is black.
I don’t know why this…
If you are saying you are importing/appending the Atmosphere object, you also need to import the Sun object, otherwise there is nothing illuminating the sky.
No…I’m saying that when you go to file->open you can choose (in a sidebar) to load (or not) the UI of Blender used by the file creator.
In your case, if I load your UI, the sky is visible, if not the sky is black
Oh interesting 
… didn’t know you could do that.
Then the reason of it rendering black is because I set the Clip End value in the viewport to 10000 km, so that the whole sky object is visible and not clipped.
Hello,
Wow, very useful, thank you so much for sharing !
