Interpolation

The process of computing intermediate values in a series of numbers. In astrology it is applied (1) to computing a planet's position for a given moment between two known posi- tions, such as the noon or midnight position prior to and subsequent to the desired moment, as taken from an Ephemeris for that year; and (2) to compute the house cusps for an intermediate 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. v. Logarithms.