The names of the six stars in Nan Dou are Dou Su I, Dou Su II, Dou Su III, Dou Su IV, Dou Su V and Dou Su VI, which are arranged in the shape of the Big Dipper. In ancient China, it was called Nandou Six Stars, which was famous for its appearance. This area belongs to Dousu for 28 nights and is located in Sagittarius.
The decline of Nandou shows that Nandou Star is already in the west and belongs to the dead of night.
I hope it can help you solve the problem.