NavList:

They must have been developed when the Portuguese voyages were nearing the equator; indeed Portuguese historians of the 16th century are recounting just that (King Joao II summoning the "Junta de matematicos"). The first printed tables that give values of the sun's declination for every day can be found in the "Regimento do estrolabio" which was printed ca. 1509 and may have been preceded by an earlier edition in the 1490's. There is only one copy known in the Bayerische Staatsbibliothek in München which was first mentioned by Siegmund Günther and recognized as a navigation manual by Joaquim Bensaude who also published the first facsimile edition with a commentary. You may consult Luís de Albuquerque, Guía Náutíco de Munique e Guía Náutíco de Evora. Lisboa 1991, on this earliest nautical publication meant for mariners.

The purpose was, of course, to make available a simple procedure for calculating latitude without too many additions and interpolations. That also accounts for 8 rules for the calculations where today one equation is enough.

Wolfgang
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