On 2020-05-01 1:12 AM (-4), Norbert Kern wrote:
> 
> I will test your settings - and I've a question - what is the suncolor value at


These are my results, with the direct sunlight normalized to luminance 1 
at whitepoint D65:

   rgb <1.301, 0.954, 0.569> (D65)
   rgb <1.106, 0.979, 0.788> (D50)

Note that my calculation doesn't take the Earth's curvature into account 
when calculating air mass.  I estimate that it will return horizon 

calculus textbooks for 35+ years ago in order to deal with the 
atmosphere's density gradient.  I do not know how low the Sun would have 
to go before my accuracy suffers.

For completeness, my average sky color is:

   rgb <0.129, 0.208, 0.350> (D65)
   rgb <0.110, 0.213, 0.485> (D50)

Getting from an average sky color to an actual sky is the hardest part. 
The sky is lighter towards the horizon, and this adds to the illusion 
that the sky is really a light blue.  Just applying the average sky 
color as a constant background makes for too dark a sky against the 
foreground objects, lending a sense of gloom to the image.  For example, 

the fog color I had to use.  To complicate matters even further, the sky 
is considerably lighter in the direction of the Sun.  So far, I have 
maintained the specified average illuminance only through trial and error.

Attached is output from Scott's sky simulator, which was based on a 
SIGGRAPH paper, via Stellarium.  The arguments were ssSunPos2 altitude 

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