Most parts of India are severely affected by light pollution (left), except for Eastern Ladakh (magnified below). Hanle, situated in this patch of almost no light pollution, is home to the Indian Astronomical Observatory and now, HDSR. The sky above Hanle are some of the darkest that are available in India, and is much sought after by researchers and amateur astronomers.
The darkness of skies is measured by amateur astronomers on the Bortle scale. A city sky would be Bortle-9 and only the brightest stars can be seen. A Bortle-1 sky is the darkest. HDSR is the largest Bortle-1 region in India. Naked eye celestial phenomena that are notoriously difficult to see, e.g. Zodiacal Light (false dawn), Gegenschein, or the shadow cast by Venus, can be routinely seen from Hanle!