all right here the bomb:
this clock dated 1500 can measure longitude with 1º error even if it delays 10 hour a day
http://itunes.apple.com/es/app/sun-m...471410762?mt=8
how it works:
you correct every day the 10 hour delay by aiming the sun and moon dial to the sun and moon as you sail away
the 24 marks graduation is wrong it was used a 28 mark graduation
so if along a 28 day trip theyre ofset 28 marks you havent moved place
now if youve traveled 360º east along 28 days needles will be offset 72 hour , you substarct one for every day trip what gives you an offset of 48 hours
so every hour of offset in that clock is 7.5º of longitude since 48 hours of offset is 360º of longitude
