With the latest update of my Cinema 4D and Chaos Corona setup (Earth Digital) it is incredibly easy to render a realistic planet.
This image was rendered like this directly from the renderer without post-processing or compositing.
Earth Digital is available on our website at www.blauwfilms.com/product/earth-digital/
The texture maps are 86K for consistent resolution at most distances from the camera.
The atmosphere shader is mathematically accurate to follow the Rayleigh Scattering principles.
It also uses a variety of atmospheric density maps to create variation within its volume.
Would love to hear your thoughts! :)