Seeing Stars

Moadim Lesimcha. The Shulchan Aruch תרלא, Halacha ג׳ mentions that the Schach should be light enough so that large stars could be seen. The Halacha continues and says that if the Schach is so thick that stars cannot be seen, the Succa is still Kosher. The Mishna Brura clarifies the matter by explaining that even if the Schach is thick like a mat, there still must be some holes somewhere on the roof, where stars can theoretically be seen. The Mishna Brura says that a far more problematic situation is where the thickness is so great that if it rains, no water would enter the Succa. Such Schach is considered like a בית. Nevertheless, even in a situation of such thickness, there are still Poskim that would even permit such a Succa.