NavList:

Hello Frank,

Thank you very much for your explanations.

My sources are :

- NA 1767, with tables for refraction and formula for parallax ;

- "Tables requisite" of Maskelyne (1781) for "classic" method (I suppose Table XIII = table XXXV of Norie) ;

- "A set of linear tables" of Norie 1815.

In fact, I have found another version in the Book of Ducom in France (same principle).

I believe to have find the principle of classic method ... this morning :

Corner formula
corr = dA * cos S = dA * ((sin A - sin A' cos D)/(Cos A' sin D)

or {dA * (sin A/Cos A' Sin D)) - (dA (Sin A' Cos D)/(Cos A' Sin D))

and the second term is also : dA tg A' Cotg D

with dA difference between true and apparent altitude and S the "corner angle".

I agree with you : the methods of Lyons, Witchell and Mendoza are similar.

I think the advantage of "linear tables" is an economy of time, perhaps with a light loss of accuracy.

Best Regards

Jacques

NB : Mendoza had proposed another method "rigourous", with is a simplificaton of Krafft method.

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