What an interesting viewpoint for (almost) canon! The astronomy professor is certainly an underwritten character in canon and it was lovely to have her fleshed out, and very interesting to have her as one of the Slytherins on the side of Light. Her celestial code was a wonderful device and her relationship with Snape was lovely. I'm not usually a fan of either him or het sex, but you managed to convince me. In fact it was pretty hot smut! An enjoyable read.