Islamic and Christian Medieval Astronomy: A Shared Heritage

These past three evenings there have been three public lectures held at the Dept. of Physics. Tonight's was on the Astrolabe, and it was given by Dr Stephen Johnston, from the Museum of the History of Science. In it he discussed the history of the astrolabe, how it works, and gave a really interesting demonstration of a little java applet of an astrolabe in action. He went through some interesting astrolabes, both Arabic and Western, as well as many others. I began to see how one might work, and how versatile as instruments they actually are. You can measure not just time, but you can also plot the planets and thus, someone's horoscope. It is so easy to forget that Chaucer actually wrote a manual on how to use the astrolabe, ostensibly at the request of his son Lewis. There are many interesting aspects to this work, not least the prologue, where he talks very directly about the nature and role of translation (for which see the very interesting article by Andrew Cole, 'Chaucer's English Lesson', Speculum 77 [2002], 1128-1167). It also occurred to me that this was a very anthropocentric way of thinking about time, at once very local (you have to use a plate with your latitude on it), and also universal, transnational. You could use an Arabic astrolabe for example in Europe with the right latitude plate and a bit of thinking.
Below is a wristwatch astrolabe, made by Dr Ludwig Oechslin at the Swiss watchmakers Ulysse Nardin. I can just imagine Lewis looking for one for his birthday! (Chaucer would have been writing a longer complaint to his purse then I rather think).