Why are you using a cubemap for your sky? A cubemap is for shiny objects to reflect the sky, not for the sky itself. The sky should be a normal texture map, mapped onto geometry with correctly set texture coordinates. I prefer skyboxes to skydomes in all cases because the texture mapping is simpler.
EDIT: Rereading your original post, I see that you are all mixed up with the vocabulary. You use the word "spheremap" to refer to a normal texture map designed to use on an object with spherical texture coordinates, and you use the word "skydome" to refer to a spheremap (you also use the word "domemap.") A spheremap, or spherical environment map, is a texutre image designed for use with spherical environment mapping, a technique to dynamically alter an object's UV coordinates. A skydome is a geometrical object (a hemisphere specifically) that covers the scene and has a texture image of sky applied to it. Domemap is presumably a word you made up.
Oh, and you use the word "cubemap" to refer to a skybox, when in fact cubemap is, like spheremap, a kind of environment map. Like a skydome, skybox refers to a geometrical object (a box this time) that covers the scene and has normal texture image of sky applied.
That all cleared up, skyboxes work perfectly fine for space. As mentioned above, I prefer skyboxes to skydomes (or skyspheres) in all situations because of the simpler texture coordinates.
EDIT: Rereading your original post, I see that you are all mixed up with the vocabulary. You use the word "spheremap" to refer to a normal texture map designed to use on an object with spherical texture coordinates, and you use the word "skydome" to refer to a spheremap (you also use the word "domemap.") A spheremap, or spherical environment map, is a texutre image designed for use with spherical environment mapping, a technique to dynamically alter an object's UV coordinates. A skydome is a geometrical object (a hemisphere specifically) that covers the scene and has a texture image of sky applied to it. Domemap is presumably a word you made up.
Oh, and you use the word "cubemap" to refer to a skybox, when in fact cubemap is, like spheremap, a kind of environment map. Like a skydome, skybox refers to a geometrical object (a box this time) that covers the scene and has normal texture image of sky applied.
That all cleared up, skyboxes work perfectly fine for space. As mentioned above, I prefer skyboxes to skydomes (or skyspheres) in all situations because of the simpler texture coordinates.