Yeah...my NEWTs astronomy class is beginning to come back to me, now.

The potion should help, with getting a clear memory. I hope. I think I have to note the time, particularly. Which might be a bit of a problem, since I won't be wearing a watch. I'm not allowed to bring metal. But if I take particular note of the time when I leave for the rite, and then make a point of looking up and noticing the constellations right when I arrive...yeah. That might do it.

That is, of course, as long as they come to fetch me at night, which is what I'm hoping for. And there's not too much cloud cover.

Very good suggestion, Pomona. I should put it into action. Thanks.