atmosphere_color has incorrect default. Screenshots for a planet with platform_backdrop = {}: and with platform_backdrop = {atmosphere_color = { 0.095, 0.15, 0.19, 0.1 }}: . The actual default seems to be { 0.095, 0.15, 0.19, 1.0 } (1.0 instead of 0.1 in alpha channel)
specular_color and light_color are not actually multiplied by 10 in the shader. Only atmosphere_* colors are.
[2.1.8] Inaccuracies in PlatfomBackdrop documentation
Re: [2.1.8] Inaccuracies in PlatfomBackdrop documentation
Thanks for the detailed post, all fixed for the next doc release.
I'm an admin over at https://wiki.factorio.com. Feel free to contact me if there's anything wrong (or right) with it.

