The mariner's astrolabe

Descriptions of the 65 astrolabes recorded, as of the time of witing in 1988, in the register maintained by the National Maritime Museum, Greenwich. Of these, nos. 1-21 had been described in D.W. Waters, The sea- or mariner's astrolabe (Coimbra: Junta de Investigações do Ultramer,1966); nos. 22-65 were added in the intervening period. "This study is closely modelled on Waters' earlier paper although the historical documentary evidence has not been repeated in full. The diligent student is advised to refer back to the 1966 paper. I have, however, reused parts of the 'notes on individual instruments', where they still apply, of the original twnty-one astrolabes and the Type numbers devised by Waters to classify the instruments. To this classification I have added two more types ..."--Page 11.