I thought I would share my experience with rendering a planet in Blender, one thing that became clear to me (after hours of rendering a video) was that my shadows were far to harsh. Exactly how sharp a shadow on a planet should be is probably a scientific principle that doesn’t change but I always adjust things until I like the way it looks.
A few things about my scene I am using the Cycles Render Engine and my planet is very small just under 1m (I couldn’t be bothered to get the real dimensions and distances of Mars). My Scene is lit with one point light at an intensity of 500000W.
Basically the larger the light is the softer the shadows become so below I have a few examples of my Mars renders with different light sizes.
First a light size of .25M this is the default size.
1m looks better
5m looks more realistic
25m also looks much more realistic
100m is too big an illuminates too much of the planet.
There you go, I hope this visualization helps in some way I settled on a light size of 20m in the end, however I will probably change my mind again…