This is really my n-th try to model a planet. It looks like you need at least 2000x2000 px for terrain, textures and clouds to not see pixels when zooming in. The starship is just a foreground from another project.
CCs are welcome 
Hi,
that flares are so bad, and the texture of te earth is so bad too. But itâs a good starter. :Z
You only need (in theory) a texture map the same size as the final image.
i.e. your final image is 640 x 480, so any size larger than this and the pixels are just getting recompressed into a smaller size. in saying that, it does pay to have slightly larger than final resolution, as this helps maintain some crispness to your textures.
also remember to turn the âfilterâ value right down on large (and important) textures.
Hi. Thanks, but this is not earth. I think itâs some dessert Planet with some oceans around the continents.
btw. to say only âbadâ does not tell me anything (in terms of feedback)
also remember to turn the âfilterâ value right down on large (and important) textures.
Aha, what does that filter do? I did not touch that slider so far Maybe this was the problem 
⌠Iâll try it - Thanks!
not sure what its purpose is, other than to be turned down. turning it down de-blurs the texture somewhat.
I have made this project as WIP now because compared to mechanical things planets are rather hard to model realisticly and I will continue on it.i
https://blenderartists.org/forum/viewtopic.php?t=48022
I tried the filter and I cannot see a noticeable difference in the land textures. Maybe because of the high res image. But the ocean Nor is now much better so see with filter = 0.1. Cool hint 
Reminds me of the original Star Trek series except your ship looks more real.