TECHNICALLY

• TECHNICALLY
  Why do you need 30min worth? and is that real time IE; 30min@24frames/sec ? OR 
  do you want Time lapse?
  What resolution are you after? NTSC/PAL, 720, 1080?
  Justin's right just use a loop any 30min file at a reasonable quality would be huge

ARTISTICALLY

What type sky are you after sunny, coloured, stormy? You might be best posting a photo

I try and help if I can ~ Peter