The culmination of a life's work that included a private war with the Royal Navy saw the adoption of the Ship's Chronometer invented by Harrison.

I believe that Cook may have taken one with him. He would also have had the (not exacltly brilliant)lunar tables. These tables are now co produced by the Admiralty and the Jet Propulsion laboratory in the US. The Nautical Almanac.

The sun moves through the stellar background once an year. (This is the 24 hour year used in the bible prophesies.) Each night you will see a slightly different stellar aspect as the sun moves to blot out another constellation. These twelve divisions give us our months. (Another biblical first.)

Someone at the same latitude will see the same as you more or less. Someone directly opposite you will be in the other hemishere and see stars you may never and not see stars that you might see any clear night.

It is an interesting subject and if you get a chance to see a southern hemisphere star chart you will be quite confused if you know your way around a northern sky.

A good way to spot the constelation stars is to flash a light in your face then look at the sky. The first stars to be seen will be the brightest. The brightest stars are known as navigatable stars. When you learn to recognise them you are quite literally on your way.

• Harrison - cheshirekate - September 24, 2001 - 16:56 UTC