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I sent some of the messages relating to this topic to Corradino Astengo in Savona, Italy, and he sent this first reply. I asked his permission to post it
on MapHist, and he added the 2nd reply and said posting it was fine.
        Ed Dahl

Begin forwarded message:

Date: December 28, 2011 3:07 AM
To: Ed Dahl <>
Subject: RE: Odd Numbers on an Old Wind Rose

Dear Ed,
I agree with Joaquim Alves Gaspar and Wolfgang Köberer. It is an application of the "Regimiento", but the figures have been rounded so it is impossible to say if it is the original (Evora and Munich) or the one corrected by Pedro Nunes. Everything is clearly explained in the book by Joaquim Bensaude, L'astronomie
nautique  au Portugal a l'époque des grandes decouvertes, Berne 1912/17,
reprinted by N. Israel in 1967.

On Dec 28, 2011, at 10:50 AM, Corradino Astengo wrote:

I agree also with Vladimiro Valerio: the system of the "Regimento" is the same as the "toleta", but it is in a way more refined, because you don't need to calculate the miles (or leagues) sailed, which is always very difficult, in
order to know your position. It is sufficient to follow a rhumb and to
calculate your latitude. You might also keep track of the miles sailed in order to compare the two different observations, but it is suggested, in case they are different, to use the one calculated with the latitude. The "Regimento" is also a
system to calculate the longitude.
Fernando Colombo at the Junta de Badajoz gave in 1424 a "parecer" in which he stated that to resolve the problem of Moluccas it was necessary to calculate their longitude and he suggested five different methods to do it, the first of them is this one, even if he admits that it is unsafe "por la imposibilidad que
hay de caminar el navio por reta linea".

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