I downloaded this skydome texture: but I can't find a skydome tha works , I tried the default and the coruscant and got this when I looked straight up:
Is there a way to fix this or do I have to try every skydome?

Is the distorted skydome picture from in game or from zero editor?
If the pic is from zero editor then try your map with the custom skydome in game,

because I've had zero editor do something similar to me when the sky is in zero editor,
but then fixed in game.

No that pic is one from ingame.

Oh, wait did you make the sky dome yourself and then apply the sky .tga or are you using a tested and true sky dome that works and then applying your new .tga?
P.S. I'm not to knowledgeble on sky dome stuff other than changing a stock sky to another stock sky, so I'm just sort of picking at straws as to the answer.

Did you resize the sky before you added it?

Try as Xterminator suggested, your picture is 1024 x 512 but the tgas for both Cor and yav2 are 512 x 256