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I recently purchased Seb Falk's, "The Light Ages" -- a discussion of Medieval science in general, and astronomy in particular.  I have found it enormously interesting, particularly chapter 4 where he decribes the construction and use of a particular astrolabe, made in England some time in the 1300s.  With photographs (which are interesting but sometimes not very clear to understand) and diagrams (which clarify the photos) he explains all this particular astrolabe could do.

It seems to have fulfilled something of the same role as the Nautical Almanac does, as pertains to the sun and to key stars, with the added benefit of telling the time more accurately than the mechanical clocks of the era.

I recommend this book.

Bob