there's no file to download.

you should show off the skybox a bit more, It's rather hidden behind geometry and clouds.

Also, there isn't any permission of Pyccna on the node, neither in a comment from him.
I would advice to do that first before making any other progress.

Exactly ^

There is the same map in Pyccna's map package.

This node will be removed within one week if you do not provide content for us to review.

Check my disclaimer in initial readme doc in the Warzone package.
"Do whatever you like with my content, I don't care."

I am, however offended that you've so far simply changed the skybox/cloudbox & are passing it as your own work (even though you did credit me, I request in the future you contact me before you use this much of my content to announce your own content!)

If you're just making a skybox to post, use the following series of commands for a map to avoid conflicts:
/newmap
/skybox [your skybox name & path]
/hidehud1
/screenshot (f12)

or simply use a section of skybox as the screenshot

P.S. (Critique of scenario) Mars already has 2 moons, Phobos and Deimos. Adding Ceres (another asteroid, Ceres being the largest) in Mars' gravitational field might complicate things. Jupiter's moon, Europa, & Saturn's moon, Titan, are far better suited celestial bodies for colonization.

In my opinion, blowing up spacecraft just to move a large rock seems like a waste of resources. Also, in theory, if you detonate a nuke in space, the fallout range is roughly infinite in all directions, so everything in our solar system would eventually be contaminated with radiation from the explosion(s). So if everything actually worked out with Ceres' eviction from the asteroid belt, you've possibly solve Mars' solar radiation with nuclear radiation & end up with the same problem on Earth. :)

There I updated it.

after downloading it at 7:15 on may 6th, it looks like you need to brighten your stars or remove the altogether. the stars are grey single-pixel things which do not look accurate.

http://mygimptutorial.com/the-ultimate-gimp-planet-tutorial/2

try that for making planets

and there is some very good software out there for making skyboxes, even if it's for basic textures to use in them.

That's a very nice image of Mars there. I also commend your attention to detail by flipping the image so it displays correctly in the skybox.

In doing so, I'm guessing you've anticipated the pain it's going to be trying to piece together 6 images in Photoshop. Not to mention the inability to accurately fake the FOV stretching in the corners. I would also recommend using software more suited to making skyboxes if that is your intention.

I'm surprised SkiingPenguins didn't point you to his most excellent tutorial using Terragen Classic. It is from late 2009, however it is still very useful and relevant.

Here

Don't put away Photoshop though, :) It is also very useful once you've learned the tools. If you aren't familiar with layers and masks already, I recommend you look those up too. It would make things like blacking out those stars very easy.