Steps in computation of sample chart

1. Find date, time, and place (including terrestrial latitude) of event.
   
   
2. Find planetary longitudes in the tropical zodiac for that date and time:
   1. If your planetary coordinates use right ascension alpha rather than longitude lambda, convert to longitude.
   2. Conversion formulas (if you know ecliptic declination delta): sin lambda = sin delta/sin epsilon, or sin lambda = sin alpha* cos delta/cos epsilon.
   3. Otherwise, use above formulas to compute delta and alpha for every sign of the ecliptic, as in the following sample table (with rough numbers in degrees):

      Sign	lambda	delta	alpha-difference
      1	30	11;30	27;54
      2	60	20;12	29;54
      3	90	23;30	32;12

   4. "Count off" the amount of right ascension along the equator while simultaneously "counting off" the corresponding amount of longitude along the ecliptic: use linear interpolation to get the fractional part of a sign corresponding to a fractional alpha-difference. Sample computation of lambda of moon if its alpha is 258 degrees (starting from vernal equinox):
      • 258 - 180 = 78 (first 180 degrees of alpha correspond to first 180 degrees of lambda or first six signs up to end of Virgo)
      • 78 - (27;54 + 29;54) = 20;12 (next two alpha-differences correspond to signs Libra and Scorpio)
      • 20;12 * 30/32;12 = 18;49 (linear interpolation gives degrees of sign Sagittarius corresponding to remaining 20;12 degrees of alpha)
      • The lambda of the moon is therefore Sagittarius 18;49 = 258;49 degrees in longitude.
   
   
3. Find ascendant for chosen date, time, and place:
   1. Find time interval between chosen time and nearest sunrise:
      • Compute ascensional difference or half-equation of daylight, omega, for this terrestrial latitude phi and solar declination delta_sun:
      • sin omega = tan phi * tan delta_sun,
      • and adjust the length of your local half-day or half-night (measured in degrees) by adding or subtracting omega.
   2. Use the above formula for omega to compute oblique ascensions or omega-differences for every zodiacal sign:

      Sign	lambda	delta	alpha-difference	omega-difference (for phi= 41;50)
      1	30	11;30	27;54	10;30
      2	60	20;12	29;54	8;44
      3	90	23;30	32;12	3;41

   3. Query: for which of the twelve signs do you add these omega-differences to the alpha-differences, and for which do you subtract them?
   4. Considering the above time interval between the chosen time and nearest sunrise as an amount in oblique ascension, "count off" that amount along the equator while simultaneously "counting off" the corresponding amount of longitude along the ecliptic between sun and ascendant. Sample computation of the ascendant at 12:11 AM on 1 January 2003 in Providence (where phi= 41;50), with the solar longitude being 280;11 degrees or Capricorn 10;11 degrees:
      • Current omega by the above formula is 22;22 degrees. The length of half the current night is therefore 90 + 22;22 = 112;22 degrees.
      • The time after midnight at the chosen event is 11/60 hours or 2;45 degrees: so the time between the event and the next sunrise corresponds to 112;22 - 2;45 = 109;37 degrees of oblique ascension.
      • Oblique ascension (alpha-difference modified by omega-difference) of Capricorn = 28;31 degrees.
      • 10;11 * 28;31/30 = 9;40 (linear interpolation gives fractional oblique ascension corresponding to fractional part of Capricorn in this interval)
      • 109;37 - 9;40 = 99;57 (remaining interval of oblique ascension at end of Sagittarius)
      • Oblique ascensions of Sagittarius and Scorpio are 35;53 and 38;38 (notice that I'm moving backwards through the ecliptic!).
      • 99;57 - (35;53 + 38;38) = 25;26 (remaining interval of oblique ascension at end of Libra)
      • Oblique ascension of Libra = 38;24.
      • 25;26 * 30/38;24 = 19;52 (linear interpolation gives degrees of Libra corresponding to remaining 25;26 degrees of oblique ascension)
      • The ascendant is therefore located at Libra (30 - 19;52) or Libra 10;8 = 190;8 degrees in longitude. Whew.
   
   
4. Establish the distribution of houses with respect to the zodiac. (Use the simple "equal-house" method where each house corresponds to thirty degrees of the ecliptic.)
   
   
5. Identify the primary characteristics of this planetary configuration.
   
   
6. Interpret the chart as a forecast of the future, in keeping with the principles of the Tetrabiblos.