If you don’t have any expriance with DIALux evo, I advise you to start with DIALux evo tutorial 4 which explains more basic function of the software that might not be explained here, DIALux evo Tutorial 4 could be found @
After you finish your project, create a sphere with Diameter of 220 meter , if you have high rise building then you might need to increase the sphere diameterKeep the segments 16 otherwise calculation will take mush longer time at not much diffrance in the output.
Insert another smaller sphere ,say 200 Meter dimeter.If you insert sphere over another, it could be rotated,so make sure the rotation for all angles is set to zero.
Select both spheres and go to copy and arrange tool, center x,y,zThen make sure to select the bigger shpere and Subtract
If your site is not big enough drae circular floor element big enough to cover the lower part of the sphere
You can either use the sky material in DIALux catalouge matirials or you could import a new one for the shpere
Use the right size that makes the shpere apear as a sky
The sphere now apears a sky
You could import anther file with exactly same texture but with a moon to be applied to only one surface
Apply the texture with the moon to only one surface using apply commandscale the texture to make it only one moon!
After calculation make the bightness higher if need be form the display option