> is this maybe because of the altitude? I had similar thought when I visited Lake Titicaca (3812m surface elevation) and looked up while standing on a small h

> is this maybe because of the altitude? I had similar thought when I visited Lake Titicaca (3812m surface elevation) and looked up while standing on a small hill on the shore - the sky had super deep blue shade at the zenith, even at noon. Very uncanny, I'd not seen anything like that before or since. I guess it was a combination of lower air density, high altitude, little air pollution and great horizon distance letting me notice contrast between white sky in the distance and dark blue sky right above. Last point would explain why I have never seen this effect in even higher mountains.