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How to Figure the Vertex in Astrology

Knowing when you are more open to allowing something or someone more easily into your life than usual is a function of the Vertex in the astrological chart. It is a calculated point found between the fifth and eighth houses of the birth chart that represents the intersection of the earth's ecliptic and the Prime Meridian. Its effects are activated when transiting and progressed planets come into conjunction with it.

Things You'll Need

American Book of Tables
American Ephemeris at Midnight

Instructions

- 1
  Calculate the Local Sidereal Time from your birth time: Write down your birth time in Standard Time adding 12 hours for an afternoon or evening birth and subtracting one hour if you were born during daylight saving time. (For example, if a birth time was 2:38 p.m. June 23, 1953 in Boston, Mass., that would be two hours (for the 2:28) plus 12, minus 1 equals 13 hours 28 minutes.
- 2
  Determine the number of hours time difference between your birth time and Universal Time in Greenwich England. (This is shown on Table 1 of "The American Book of Tables," or "ABOT.") If you are west of England, add this number to the hours of your birth hours. If it is east of England, subtract that number. (In our example, because Boston is five hours from Greenwich we add five. Thus, Universal Time equals 18 hours 28 minutes.)
- 3
  Look up the sidereal time for your birth date in the ephemeris. (For our example, it is 18 hours 3 minutes.)
- 4
  Look up the Solar Sidereal Correction Time on Table II of "ABOT" if you want your Vertex to be within several minutes of accuracy using your calculated Universal Time. (In our example, look under the column of 18 hours to where it intersects with 28 minutes and get the answer of 3 minutes, 2 seconds. Add the ephemeris time to the Solar Sidereal Correction to the sidereal time to get the Greenwich Sidereal Time. (In our example, the answer is 36 hours, 34 minutes.)
- 5
  Correct for longitude distance from Greenwich by using Table III in "ABOT." (In our example, because Boston is 71 degrees of longitude, the longitude correction is 4 hours 44 minutes.) Subtract these figures from Greenwich Sidereal Time. (In our example: 36 hours 34 minutes minus 4 hours 44 minutes equals 31 hours 50 minutes). Subtract 12 hours from your answer. (Corrected longitude in our example is 19 hours 50 minutes.)
- 6
  Find your colatitude. Subtract your latitude from 90 degrees. (In our example, the Boston location's latitude is 42 degrees North 21 minutes. Subtracting this from 90 degrees, convert the 90 degrees to the equivalent 89 degrees 60 minutes. 60 minus 21 equals 39; 89 minus 42 equals 47. Thus, the colatitude is 47 degrees 39 minutes.)
- 7
  Look up an ascendant figure in the Placidus Table of Houses in "ABOT" for your corrected longitude. (Example: 19 hours 50 minutes.) Follow the column down to the colatitudes degree (47 degrees in our example). Note the degree for Ascendant. This is your Vertex.

Astrology