This compilation of house cusps is an authoritative reference for the accurate division of the zodiac into twelve houses. Designed to meet the most demanding needs of astrologers and those doing astrological research, the tables cover the range of latitudes from 0 to 66 degrees and list all cusps to one-tenth of a minute of arc. The tables list the cusps at even four minute intervals of sidereal time, making linear interpolation practical and straightforward.
There are 360 separate tables of house cusps with each showing the house cusps for latitudes 0 to 66 degrees at a single value of sidereal time. At the top of each table the sidereal time is printed in hours, minutes, and seconds on the left, and in degrees, minutes, and seconds on the right. Since the Midheaven remains the same for all latitudes, it is printed once at the top of the page, and because of its importance is listed to a precision of one second of arc
The general rule for finding southern latitude cusps is to add twelve hours to the sidereal time, look up the cusps as if the latitude were north, and then reverse the zodiacal sign of all the cusps found. This process is made easier in this volume through the use of separate headings for southern latitudes at the bottom of each table. Instead of adding twelve hours to the sidereal time, use the sidereal time headings at the bottom of the page when locating the proper table. This gives the same table that would be found by adding the twelve hours and using the northern latitude headings.
It is usually necessary to interpolate to find cusps for an exact time or latitude that falls between two listings in the tables. Interpolation is the process of finding a small correction to be added or subtracted from a cusp in the tables to compensate for the difference between the value of the cusp at the listed sidereal time or latitude and the value of the cusp at the actual sidereal time or latitude. Generally speaking, interpolation must be done twice for each cusp: a correction for the sidereal time and another for the latitude. The Midheaven need only be corrected for sidereal time since it remains the same at all latitudes.
It is no surprise that the difficulty of interpolation depends upon the accuracy required. Included in this book are explicit instructions for three techniques for finding the house cusps, each of which gives successively more accurate results. All tables needed for all three techniques are included in the book.