identify the constellations and stars every day of the year. Just dial in the date and time by rotating the inner plastic disk showing the time until it lines up with the relevant day of the year on the outer ring. The part of the sky appearing on the planisphere shows the arrangement of the stars above you. This star chart is suitable for use anywhere in Britain and Ireland, Northern Europe, Canada and Northern USA. Best viewed as near to latitude 50 degrees north as possible. The moveable disk also comes in a wallet which contains further information about stargazing. The Planisphere comes with instructions both inside this card and on the back of the Planisphere itself. The Royal Observatory, Greenwich is the home of Greenwich Mean Time and the Prime Meridian of the World, making it the official starting point for each new day and year. It is also home to London's only planetarium, the Harrison timekeepers and the UK's largest refracting telescope. "This twin set of Guide and Planisphere is ideal for novices to learn their way around the sky visible to observers around latitude 50 degrees North." The Observatory magazine"