A detailed introduction to the city of Dunhuang, the first place foreigners entered from the south. The photograph of the sand dunes surrounding the Magao Caves looks exactly the way it did when I was there. 
This brief introduction to the star chart taken by the British can be supplemented by this more detailed study. The image in the book is the tattered copy that remains in the Dunhuang County Museum. At the time I visited, the staff had no idea what it was, and had no trouble with photographing it.
The oldest cave (275) has one of the most spectacular images of Buddha. Another amazing statue is the sleeping giant, best captured in this image from China.net. 
The Getty has reproduced some of the art in the many many caves in Magao . The site is worth looking at, because you can study the images in detail, something you cannot do during the airless, stifling hot, and overcrowded visit to the caves. This Sleeping Buddha is even more impressive in person.
North and South Silk Roads through China. The star maps were found in the Magao Caves in Dunhuang, China marked by green star.
View Dunhuang, China and the Silk Road in a larger map