I found a beautiful catalogue of Astrolabes put together by the National Maritime Museum in Greenwich
which has a fantastic collection of them. Again, this book stayed in front of me while I was writing. Then, when I was done, I passed it on to Dave, who found it as breathtakingly beautiful as I had. And again, I think he did something extraordinary with it.
Mr Ripley's Book Review: http://www.mrripleysenchantedbooks.com/2013/08/book-review-sf-said-phoenix-illustrated.html