A Philips' Planisphere, showing the principal stars visible for every hour in the year, published by George Philip & Son Ltd of London in 1960. A planisphere is a map of part of the celestial sphere that can be adjusted to match positions of the stars in the night sky for a particular time and location. It consists of an acetate disc that can be rotated over a very detailed celestial map. Round the edge are dates of the year and by simply turning the disc to the current date and the direction you are facing, the window in the acetate will show a map of the constellations in the sky above your head. It really is a deceptively simple scientific instrument as well as being an attractive decorative piece. it is still in perfect working condition.