Ken Ward's Astrology Pages

Astrology: Calculating the Ascendant - Southern Hemisphere.

The ascendant is the sign on the Eastern horizon when the birth occurred. On this page, we will use Kiri Te Kanawa as an example.

Kiri Te Kanawa born in Gisborne, New Zealand on Monday 6 March 1944 at 2pm. TZ:12.00, Lat 38S40, Long 178E01

We have already calculated Kiri's sidereal time of birth, so all we have to do is to look in the tables of houses to find the ascendant. Kiri's sidereal time of birth is:

12 hours 46 minutes 48 seconds.

This has already been corrected for a Southern birth. We procede to calculate the Ascendant in the same way we did for a Northern Hemisphere birth ... except, we reverse the signs. So if the sign is Aries, we take Libra. If the sign is Scorpio, we take Taurus. And similarly, we take the opposite sign.

The tables depend of the latitude of birth, so we need to look at the tables for the nearest latitude to Kiri's place of birth.

The American Ephemeris 1931 to 1980 contains tables of houses which we can use. There are, of course, many other sources.

The tables are organized in terms of time, each time 4 minutes different from the previous, and in terms of latitude, each latitude 1 degree different from the previous.

You can look at the tables and pick the nearest ascendant. As the time is nearer 12 hours 48, you can choose to look at the table for 12 hours 48. As the latitude is nearer to 39 than to 38, you can choose to take the value from the tables for latitude 39. The result from the tables is 22sa21.

We need to reverse the sign here for a Southern birth.

So the answer would then be 22ge21. The correct answer (22ge18) can be computed.

Accurate Computation of the Ascendant (Advanced)

Let's look at the real example of Kiri. Note I have reversed the signs found in the tables. So, although the tables showed Sagittarius (for the Northern Hemisphere), I reversed this sign to get Gemini (Southern Hemisphere birth)

Latitude	12 hour 44 mins	12 hour 48 mins
38 degrees	22ge7	23ge0
39 degrees	21ge29	22ge21

As before we want to find the mean ascendant at 12 hours 44 minutes to begin with. In this case, Kiri was born 40 arcminutes after the first latitude of 38 degress. The two latitudes above differ by 38 arcminutes. So the factor for Kiri is 40/60 or 0.6667. The difference between the two ascendants (22ge7 and 21ge29) is -38 arcminutes. We multiply this by the factor by the difference:

-38x0.6667=-25.33, say -25

We subtract this from the lower latitude's ascendant (22ge7) so:

22ge7-25=

21ge42

We do the same for the second time. In this case we have 23ge0 and 22ge21. The difference is:

-39 arcminutes

Multiplying this by the same factor as before (0.6667) we get

-39x0.6667=26.00 or 26 arcminutes

So we get the ascendant at the higher time as:

23ge0-26=

22ge34

Kiri was born (sidereal time) 12 hours 46 minutes 48 seconds. The difference in the two times is 4 minutes or 240 seconds. Kiri was born 2 minutes 48 seconds after the first time in the tables, or 168 seconds. The time factor is, therefore, 168/240, or 0.7000. The difference between the two mean ascendants (21ge42 and 22ge34) is 52 arcminutes. The amount to add to the lower value is:

52x0.7000=36.40 or about 36.

So we add this to the lower value:

21ge42+36=22ge18

22ge18 is the correct ascendant.