G'day Max
Having seen the night sky From Everest base camp, Tibet, at an altitude of 5200m I can vouch for the quality and transparency of the skies. The sky was so dark and pristine you could barely make out the patten of bright constallations like Orion. I am sure I was seeing stars well past the 7th magnitude
easily.
Oh by the way if you aclimatise slowly you probably don't need oxygen (I never used it and I'm a smoker) and the beer tastes fantastic on the roof of the world
Best of luck with your project,
Mick.