# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Proportional logs, etc.
From: Jan Kalivoda
Date: 2004 Aug 25, 23:47 +0200

```Dear Henry,

Thanks for further details. Your table set is extremely interesting as another
method from the golden era of lunars that wasn't mentioned in the literature,

I cannot say that I understand anything from your data better than you. I have only questions:

There should be items for small values of the difference (parallax -
refraction) in the Moon table, too - for her altitudes near the zenith, isn'
it? Yes, above 87 degs of altitude, maybe they are dropped from the table.
But if not, do they conform to the values found by adding the traditional
proplog of the difference (parallax - refraction) with logs of sin of 30 degs
and cos of altitude or with the values of the Sun table?

And for the Sun table: I take your table value for 30 degs of the apparent
altitude, i.e. 1.7115. If subtracting 9.6990 for log sine 30 and 9.9375 for
log cos 30, we obtain 2.075 as the proplog of 1' 30". This corresponds to the
number 118.85. And if you multiply it by 90 secs, you obtain 10696 secs as
the basis of these proplogs, instead of common 10800 secs. Are the adjacent
table values (under 2 min 50 sec of the altitude correction) conforming to
this result? For greater values of difference (parallax - refraction)  this
tiny difference of cca 104 secs for the basis can disappear in computing
proplogs to 4 places.

And what about the stars table? Whether and how do differ its values from the Sun table?

I wish you much luck with Mr. Arnold. Yours,

Jan Kalivoda

```
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