Why Spiti's sky is so dark

Altitude, dry air and distance. At 4,400 metres you are above most of the water vapour and dust that dims the sky lower down, the air in Spiti is some of the driest in India, and the nearest town of any size is a day away. On a moonless night the Milky Way is bright enough to throw a faint shadow.

Written from the verandah, with a cup of chai going cold.