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From: Bruce Stark (no email)
Date: Thu Aug 26 2004 - 19:39:13 EDT
Henry,
As for how to calculate proportioning logs:
They are for a three hour interval, and designed to proportion to the nearest
second of time. Three hours contains 10800 seconds.
One hour contains 3600 seconds. So the PL of one hour is simply the log of
10800/360.
The PL of seven seconds is the log of 10800/7.
The PL of one minute, six seconds is the log of10800/66.
And so on.
Since there are 10800 seconds of arc in three degrees, PL tables can be used
to proportion small angles as well.
Hope this helps.
Bruce
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