Various mods tackle the issue in various ways. Try
http://www.subsim.com/phpBB/viewtopi...=44986&start=0 for starters. I don't know if it includes AIL's big moon or the small one. If the latter, try AIL HI RES MOON MOD V2.5 at
http://www.ailantd.com/SHIIIMODS/
Or there's
http://www.subsim.com/phpBB/viewtopi...=ocean+madness
Then there's this thread which might provide some assistance...
http://www.subsim.com/phpBB/viewtopi...highlight=moon
I found a few other threads all very similar in content (one focuses on the night sky changes included in RUb).