Logarithms - Tables by which when a planet's motion is known its position at a given time may be readily calculated.
Logarithms. Proportional parts of a quadrant, expressed in numbers, whereby calculations of the planets' places at a given hour, or the Arc of Direction for a given date, ...
Logarithms:
Were originally invented by Lord Napier to make arithmetical calculations easy. They were later adapted to the decimal system, and are used by astronomers who calculate directions by arc.
* Proportional Logarithms are useful in chart calculation, but are of no use right now. They can shorten the manual calculation process, but they are an optional tool which is going out of use with increasing computer usage.
The inventor of logarithms which appear to have been invented in part to make astronomical and astrological calculations simpler.
1558-1628. David Origanus. A compiler of ephemerides and almanacs.
1570-1657. Andreas Argolus.
Use of trigonometry was further expedited with the advent of logarithms, which rendered it more accessible.
First devised in 1614 by the Scottish mathematician John Napier who reduced complicated multiplication and division of numbers to the simpler operations of adding or subtracting their exponents (logarithms, abbreviated logs).
This is a simple way to avoid logarithms and does give the same ascendant as the computer generated chart. (Note there is a slight variance between programs) The rest of the cusps should be calculated similarly.
Tables of logarithms or planetary motion were used to do this. A table of houses was used to produce the houses of the chart (more on these later).
latitude between two sets of tables computed for latitudes on either side of that for which the interpolation is required. In making the calculations necessary for an interpolation, use is frequently made of Tables of Diurnal Proportional Logarithms.
 See also: Sun, Logarithm, Planet, Moon, House
  
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