Calculation of the Night-time Ascendant and the Tenth House

If the calculation of the Lagna: the Ascendant, or the point rising on the eastern horizon at the moment of birth is performed for a birth at night, then the calculation should be made from the position of the Sun increased by Rashishatka: six zodiac signs, or 180 degrees. Similarly, when calculating the Dashama-lagna: the Tenth House or Midheaven at night, the "remaining portion" to be calculated should also be based on the Sun's position increased by six signs. Here is an example to illustrate this:

Rising times at the place of birth

These values represent the time in 'palas' (one-sixtieth of a ghati) that each sign takes to rise at the specific latitude of the birthplace.

The rising times at the birthplace are as follows. The Tatkaliko-arka: the "Current Sun," or the precise longitudinal position of the Sun at birth is 9 signs, 7 degrees, 30 minutes, and 6 seconds. When the Ayanamsha: the value for the precession of the equinoxes of 18 degrees and 26 minutes is added, it becomes 9s 25° 56' 06". The degrees remaining to be traversed in the current sign are 4° 03' 54". This is multiplied by the rising time of Makara-rashi: the sign of Capricorn (which is 298 in the table) and then divided by 30. This produces the Bhogyakala: the remaining time left for the sign to finish rising, which is 40 minutes, 22 seconds, and 44 thirds.

This value is subtracted from the Ishtanadi: the desired birth time elapsed since sunrise, which is 12 ghatis, 18 minutes, and 30 seconds (converted to 738 minutes and 30 seconds). The remainder is 697:16.

From this remainder, we subtract the rising time of the sign following Capricorn, which is Aquarius (239). The remainder is 458:37:16. Next, we subtract the rising time of Pisces (203). The remainder is 255:37:16. Next, we subtract the rising time of Aries (203). The remainder is 52:37:16. The rising time of the next sign, Taurus (239), cannot be subtracted from the remaining 52:37:16 because it is larger. Therefore, we multiply the remainder by 30 and divide it by the rising time of Taurus (239). The result is 6 degrees, 36 minutes, and 18 seconds.

By adding this to the signs already passed (Aries being the 1st sign), we get 1 sign, 6 degrees, 36 minutes, and 18 seconds. After subtracting the precession (Ayanamsha) of 18° 26', the true Ascendant is found at 0s 18° 10' 16" (Aries). By adding six signs to this, we find the Jayabhavana: the "House of the Wife" or the Seventh House to be at 6s 18° 10' 16" (Libra).

Now, for the example of the Tenth House calculation, we use the Lankodaya: the rising times of the signs at the Equator (Lanka):

Table of Equatorial Rising Times

The Sun's position is 1s 02° 44'. The time past noon (or birth time) of 12 ghatis, 18 minutes, and 30 seconds is processed to find the "noon-offset," resulting in 0:25:30. This is the "desired time." Using the equatorial rising times, the portion of the sign already traversed by the Sun is multiplied and divided by thirty. The "elapsed rising time" is found to be 279:14:00. This cannot be subtracted from the 25:30 time units, so the 25:30 is multiplied by thirty and divided by the rising time of the sign (323). The result is 2 degrees, 22 minutes, and 6 seconds.

Subtracting this from the Sun's position (9s 07° 30' 06") gives 9s 05° 08' 00". Adding six signs to this gives the Sukhabhavana: the "House of Happiness" or the Fourth House at 3s 05° 08' 00" (Cancer). The difference between the Ascendant and the Fourth House is 2s 16° 54' 44". Dividing this by six gives 0s 12° 49' 37". Adding this value to the Ascendant gives the Viram-sandhi: the junction or boundary of the Ascendant at 11s 00° 59' 53". Adding the Shashtamsha: the sixth part of the house division again gives the start of the Second House at 11s 13° 49' 30". Adding it once more gives the junction of the Second House at 12s 06° 39' 07".