Logarithms · Astrological definition of Logarithms · Astrology Encyclopedia  ·  August 11, 2024, 2:19 GMT

Right now: Moon at 1°51' Scorpio, Sun at 18°56' Leo

# Logarithms

## Logarithms - Astrology Encyclopedia

Definition of 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, can be made by simple addition and subtraction rather than by multiplication or division. They were invented in 1614 by Baron Napier of Murchiston for use in his astrological calculations. Tables of Logarithms are in common use in all schools by students of trigonometry. Tables of natural, proportional and logistic logarithms are also available, each designed for different uses. An improvement in logarithms was introduced by Henry Briggs in 1624.

The astrologer uses Diurnal Proportionate Logarithms in making numerous calculations, but their average use is in calculating the planets' places for a given birth hour. If it is desired to reduce daily motion to hourly motion by the use of Logarithms, proceed as follows:

Subtract the positions of the desired planet on two successive days to determine its daily motion. Also compute the elapsed time between your birth moment adjusted to local mean time, and the previous noon or midnight - dependent on whether your ephemeris for that year gives noon or midnight positions.

Suppose you are seeking the Moon's position for an elapsed time of 7h 35m on a day in which its daily motion is 14° 27': In the tables, select the column with 14 at the top; run down the column to 27; and set it down; also for 35 in the 7 column; thus:

D.M............ 14º27' prop. log. .22034

Elap.T. ....... 7h35m prop. log. .50035