The Tibetan plateau is one of the best places on earth to look at the night sky, and the reasons are physical: very little artificial light, extremely low humidity, high altitude with correspondingly thin atmosphere, and in winter some of the steadiest air in the world. Around Namtso, the great salt lake north of Lhasa, and across the Changtang grassland, the Milky Way is visible to the naked eye as a dense band of light rather than a faint smear, and the sky between the stars is properly black.
Why the plateau is different
At four and a half thousand metres there is roughly half the atmosphere overhead that there is at sea level, so less light is absorbed and scattered, and the dry air holds very little water vapour. The practical consequences are that stars are visible closer to the horizon than in Europe or North America, that colour in bright stars is much easier to see, and that the Andromeda galaxy and the Orion nebula are naked-eye objects. Seeing the Milky Way cast a visible shadow is a real possibility on a moonless night.
Where and when to go
Namtso and its surrounding hills are the usual base for visitors, with guesthouses and tent accommodation beside the lake. Farther north and west the Changtang is darker still but far more difficult to reach. The best months are the cold ones - October through March - when the air is driest and the nights longest, but those nights drop well below freezing and the roads can be affected by snow. Around the new moon is the time to plan for, since a bright moon wipes out everything but the brightest stars.
Practical notes
Foreign visitors need a Tibet Travel Permit plus a permit for travel outside Lhasa, arranged through a licensed agency, and Namtso is a scheduled stop on most approved northern itineraries. Altitude is the main risk: nights at Namtso are close to 4,700 metres, and spending the night there should follow proper acclimatisation in Lhasa. Bring a tripod, spare batteries kept warm, a headlamp with a red filter, and more insulation than you think necessary - lying still in the cold is different from walking in it. Take care near the lake shore at night, where the ground is uneven.
