AFAIK the WiH skybox is something different. It has more stars and is a cube.
All War in Heaven skyboxen are fundamentally cubes. These are cubes too, and there's three different brightness levels supplied for both 2048 and 4096 resolutions.
However I don't remember if Blue Planet ended up using exactly these textures, or if I made some with increased brightness. It's entirely possible.
The HT's skyboxes which I want are spherical.
I don't think I ever released these in spherical form. If you wanted a spherical skybox, you could just grab the raw file from NASA, apply brightness/contrast/level edit it to your satisfaction, and simply apply it to a sphere and call it a day.
But I would counsel against it. Spherical skyboxen are not as memory efficient as cubic skyboxen.
8192x4096 spherical texture corresponds quality-wise to a cubic skybox made of six 2048² textures.
8192 * 4096 = 33 554 432 pixels
6 * 2048 * 2048 = 25 165 824 pixels
What that means is an arrangement of six 2k textures uses 75% of the memory a single 8192x4096 texture, with practically identical quality.
And if the performance argument fails to convince you, there's also the fact that smaller textures are more accessible by low end hardware. For example, if you have a graphics card that has maximum resolution of 4096², you simply cannot use a spherical 8192x4096 texture because it's just too large. However the graphics card could be perfectly capable of using six 2048² textures...
As for Milky Way panorama from Dreamscape, I think it's coming from Syrk Demo. Rodo was the author if this is the same skybox.
No. The Milky Way in Dreamscape is my work. It uses an edited version of HTSB starfield on the background, but it has an additional galactic plane overlayed with it to make it a bit more unreal. There have been similar skyboxen elsewhere, but that one is mine.
Both of them are cool, but I wanted something darker for my Sol 
.
If you insist on using a spherical skybox, then NASA's Tycho-Hipparcos maps are already in correct format as far as dimensions go. However you probably want to apply some kind of edits to them to get the effect you want - black level, white level and gamma, most likely.
You can also take the cubic skyboxen I have provided here, and edit them to create your own version. It's not like I did much else than project the original texture to the sides of a cube... just remember to credit NASA/Goddard Space Flight Center Scientific Visualization Studio for the original textures. The POF model for the skybox was provided by peterv.
