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Things You'll Need
Instructions
Calculating the Birth Time
Draw a circle on a blank sheet of paper. Divide it into 12 sections to make an astrology chart. Set aside.
Get the birth time and location for the horoscope. Use an atlas to obtain the geographic coordinates and time zone. For example,123 degrees and 6 minutes west of Greenwich, Pacific Standard Time Zone.
Look at a time zone map to find the zone's central meridian. For Pacific Standard Time, the meridian is 120 degrees west of Greenwich. Count the number of degrees and minutes that the birthplace is off the meridian. In the above example, it is 3 degrees, 6 minutes west.
Add 4 minutes per degree and 4 seconds per minute to the difference. The result here is 12 minutes and 24 seconds.
Subtract the above figure from the Standard Time if the birthplace is west of the Standard Time meridian; add the difference if it is east of the meridian. If the standard birth time is 6:00 a.m., the result is 05:47:36 a.m. (rounded off to 05:48 a.m.), the Local Mean Time.
Calculating the Houses
Find the Sidereal Time for the birth date in a noon ephemeris. For example, the sidereal time for noon in Greenwich on January 1, 2001 is 18:44:50, according to the "Astrolabe World Ephemeris 2001-2050."
Calculate the difference between the Local Mean Time of birth and the previous or coming noon. For 5:47:36 a.m., the difference is 6 hours, 12 minutes and 24 seconds. Add the interval to the Noon Sidereal Time if the birth is after noon; subtract if it is before noon. 18:44:50 - 06:12:24 = 12:32:26.
Accelerate the difference. Add 10 seconds per hour, or 1 second per 6 minutes. For this example, the total is 62 seconds. Add the result to your calculations if the birth was after noon; subtract if it was before noon. 12:32:26 - 00:01:02 = 12:31:24.
Correct for longitude. Add 10 seconds per 15 degrees if west of Greenwich; subtract if east of Greenwich. The result is the Local Sidereal Time. 12:31:24 + 00:01:22 = 12:32:46.
Find the chart's latitude in an astrological tables of houses. Look up the time closest to the Local Sidereal Time above. In the Rosicrucian "Tables of Houses," the closest to 12:32:46 is 12:33:04.
Copy the house cusps listed there to your astrology chart. Write the degree, sign and minute of each cusp on the outside of each house.
Calculating the Planetary Positions
Refer to the ephemeris for each planet's position on the birth date. Subtract this from the next day's position if the birth is after noon. Subtract the previous day's position from the birth date's position if it is before noon. Reverse this rule if the planet is retrogade (i.e., temporarily appears to be moving backward).
Convert the planet's motion into a logarithm. For example, the equivalent log for 1 degree of motion is 1.3802, according to the Table of Proportional Logarithms given in "The A to Z Horoscope Maker and Delineator."
Calculate the difference between the Greenwich Mean Time for the horoscope and the Greenwich Noon Time. A birth time of 5:48 a.m. Local Mean Time in the example chart has an equivalent time in Greenwich of 2:00 p.m. The difference is 2 hours.
Find the logarithm for the difference. According to the Table of Proportional Logarithms, the log for 2 hours is 1.0792.
Add the above log to the planetary motion log. For this example: 1.3802 + 1.0792 = 2.4594.
Convert the logarithm into motion. Look for its closest log in the Table of Proportional Logarithms. If the nearest or exact log listed is 2.4594, the equivalent motion is 5 minutes.
Add the motion to the planet's position if the birth is after Greenwich noon; subtract if it is before noon. (Reverse this rule if the planet is retrogade.) If the sun's position at noon in Greenwich was 11 degrees, 08 minutes Capricorn, this gives 11 degrees, 13 minutes in the same sign.
Place the planet in your astrology chart. Use the house cusps to find its correct position. Repeat the above calculations for the other planets until the horoscope is completed.