How to tell the time in the dark

Alethea Kemp of The British Museum holding a 400 year old Nocturnum Horologium, a device used to tell the time in the dark. If you know the date, position the dials accordingly then viewing the pole star though the centre, point the side bar to the end of the constellation. Time is then indicated.

I'm here by accident as I went to Falkiner Fine Paper, leaving my purse behind. I had to return home but had 20 minutes on my parking meter. Not wanting to waste it, I came in to the British Museum.