Quote - If you want really blue skies, try this:

AttributeBegin
LightSource "sunsky" "integer nsamples" [1]
            "vector sundir" [0.70000 0.400000 0.700000]
        "color L" [1.000000 1.000000 1.000000]
        "float turbidity" [2.000000]
        "float aconst" [0.500000] "float bconst" [0.500000] "float cconst" [1.000000] "float dconst" [1.000000] "float econst" [1.000000]
        "float relsize" [2.000000]
AttributeEnd

This is from rty's post several pages back

Linked pic is using this.

Just read this and now looking at your settings

Physical sky light

The physical sky creates a lighting setup that simulates the light of the sun and atmosphere, based on the direction of a sun lamp in the scene and a parameter named turbidity which defines the clearness of the sky. Both the sun angle and the sky clearness influence the colour of the light.

Additional parameters called aconst, bconst, cconst, dconst, econst allow you to fine tune the color of the sky to simulate various atmospheric conditions.

Where did you set the Sun Angle?
or is that this part?
 "vector sundir" [0.70000 0.400000 0.700000]

Thanks,
 

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Thomas Jefferson