The Nova of Madagon is a spacial location lying somewhere between the Twelve Colonies and the planet Carillon.
It is not actually a nova at all, but is a starfield of intense, blinding brightness; this "nova" also causes electronic equipment problems for smaller craft. The Straits of Madagon, a passage within this area of space, were mined by the Cylons, though these are cleared by a group of three Vipers lead by Captain Apollo (Saga of a Star World).