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Way to cast a horoscope

To caste a horoscope, following accurate details are required:

Date of birth
Time of birth 
Place of birth.

Time of Birth: It is recorded for India as IST - Indian Standard Time (and for other countries as GMT - Greenwich Mean Time). GMT is 5½ hours ahead of IST. But for casting a horoscope, Local Mean Time is used, which depends on the place of birth.

Place of Birth: Logitude and latitude of the place of birth are used to find the time correction to be applied to the IST, to find out the Local Mean Time.

Longitude: It is the arc drawn from North Pole to South Pole to mark the location in degrees of a particular place from a central place (Greenwich). All places are located either to the West or to the East of Greenwich. For example, the longitude of Bombay is 72° 50' E.

Latitude: It is the arc drawn to mark the location in degrees of a particular place North or South of Equator. For example, the latitude of Bombay is 18° 58' N.

Sidereal Time: It is the time taken by the earth to make one full rotation. It is not exactly 24 hours, but goes on changing according to increase or decrease in the duration of days and nights. It is called Vernal Equinox time and it is a measure of earth's rotation with respect to the equinox, which has a very small retrograde motion. Sidereal time is used for calculation of the Ascendant.

CALCULATION OF ASCENDANT

For making the horoscope, first of all we have to calculate the Ascendant. Ascendant is the rising sign at the time of birth. Let us see how the Ascendant is calculated. This will be done with the help of two books, viz. Table of Ascendants, and Annual Ephemeries, 1993 (for the year of birth) by Lahiri. These two books can be procured from the market.

Details of sample birth are once again given below.  We would calculate Ascendant for this.
Date of birth          :        10.12.1993,
Time of birth          :        3.50 AM IST
Place of birth          :        Bombay.

We have indicated the Longitude and Latitude of Bombay as above. These were taken from page 101 of the book "Table of Ascendants". This book contains the necessary information about many major cities of India and abroad. If the city required is not given therein, kindly see the Atlas for these details. And, if Atlas is not handy, nearest city can be taken. But for accurate casting of horoscope, accurate details are required.

As made clear earlier, in a northern horoscope, Ascending sign is written in the top centre and then zodiac signs are continued anti-clockwise. Later on planets are placed in the horoscope. So, to calculate the Ascendant sign, the first Step is to find out the Local Mean Time (LMT).

Step 1

Convert the IST to LMT.  There are two ways to find out the correction time to IST to obtain LMT::

i.  Take the Longitude of Bombay, i.e. 72° 50' N.

Formula for getting the correction time to IST to find out LMT is  15° = 1 hour, or  1° = 4 minutes
(Please note, Longitude is given in degrees (°), minutes (') and seconds (''), [ 1° = 60', 1' = 60''), whereas the time is given in hrs, minutes and seconds [1 hr = 60 minutes, 1 minute = 60 seconds].  Do not confuse the minutes of Longitude with the minutes of time.                
As per above formula, divide Longitude 72° 50' by 15 to know the LMT.  It comes to: 4 hr 51 mt 20 secs.  How?  This is shown below to facilitate your understanding of the calculations.
{72°/15 = 4 12/15 (i.e. 4 hrs + 12/15 hrs)
12/15 x 60 (to make minutes) = 48 minutes
Hence, 4 hr 48 minutes
Now 50' /15 = 3 5/15 (i.e. 3 minutes + 5/15 or 1/3 minutes).
1/3 x 60 (to make seconds) = 20 seconds.
Hence, 4 hrs, 48+3 minutes, 20 seconds = 4 h 51 m 20 s.
Now deduct 5 h 30 m 0 s (as GMT is +5h 30 m 0 s of IST) from 4 h 51m 20s:
4 h     51 m  20 s
-   5 h    30 m  0  s
-   0 h     38 m  40s  

This means,  38 m 40 s should be deducted from IST to find LMT.

Step II

The next step is to find out the sidereal time for the given date, time and place of birth.

Sidereal time for 10th December
(From page 3, Table of Asc)    17 h   14 m  07 s
Correction to Indian sidereal time for Bombay (From page 101, last column, Table of Asc)                       +                     06 s
Correction for 1993 (From page 4, Table II, Table of Asc)                    +            1 m   52 s
Sidereal time for 12 Noon on 10.12.1993 for Bombay                
17 h   16 m  05s  ..B
Now, let us calculate sidereal time for the time of birth on 10.12.1993 for Bombay: As the birth is before 12 Noon, deduct from  12 h   00 m  00 s
LMT           3  h   11 m  20 s

8 h   48 m  40 s ... C

(For afternoon birth, there is no need of this deduction.  Correction to increase the time interval is apllied straight to the LMT).

Now apply correction to increase the time interval (From page 5, Table IV, Table of Asc):

for 8 hr      +  1  m   19  s

for 48 m     +           8 s

for 8 hr 48 m:  1  m    27 s  ..... D

Now, add C and D.  This comes to 8 h 50 m 07 s.

Sidereal time at 12 Noon                    17 h   16 m  05 s
Less corrected time interval           -    8 h    50 m  07 s

(For birth in the afternoon, this should be added.)

Sidereal Time for the given                  8 h    25 m 58 s ...E
birth time:

Step III

Now to find out the Ascendant, refer to Tables given in the book Table of Ascendants for various latitudes.  Search for the latitude of Bombay (or its nearest place, if the same is not available).  On page 29, Table for Latitude 19° N is given.  As given earlier, the latitude for Bombay, the required place of birth, is 18° 58' N (say, 19
° N).

In this page, we have to search for the Ascendant for the Sidereal Time given above as, 8 hr 25 m 58 s as at E.

Ascendant for

For 8 h  24 m                                     6 s     100    46'

For 8 h 28 m                                      6s      110    41'
Hence for 4 m                                                        55'
('s' is the zodiac sign, Degree (°) and  minute (') already explained above).

If we deduct the former from the latter, we get  4 minutes = 55 m but we need 2 minutes (8h 24 m + 1 m 58' (1 m 58' is approximately equal to 2') = 8 h 26 m.  So for 2 minutes, we get  28 m (55/2: 27.5, say 28).

Therefore, Ascendant  for 8 h 25 m 58 s (Or say, 8 h 26 m)

=       6 s     10°    46'

+                28'     
6 s     11    14'

Step IV

Now, apply correction for Ayanamasha for 1993, as per page 6 of Tables of Ascedants, which is -46'.

Therefore, Ascendant for the required birth: 6 s     11°    14'

-    46'

Ascendant(I):   6s      10°    28'

This means, Ascending sign is Libra (7), and it has travelled 10° 28'in Libra.


CALCULATION OF LONGITUDE OF PLANETS

Now to place the planets in the horoscopes, longitudes of planets have to be calculated. For this, we proceed as under:

1.Refer to Annual Ephemeris, 1993. Longitudes of different planets for the entire year, month-wise, day-wise, have been given as at 5.30 AM IST.  On page 30,  search the required date, i.e. 10th December.  Against this the longitudes for planets on 10.12.1993 at 5.30 AM are given.  But our required birth time is 3.50 AM, i.e. 22h 20 m after 9.12.1993 at 5.30 AM.

2.Find out the longitudes of planets as on 9.12.1993 at 5.30 AM from page 30, and add the distance covered by planets in 22 h 20 m.  This can be done in the following way :

Find out the longitudes of planets as given below :

--------------------------------------------------------------------------------------
9.12.1993                   10.12.1993           Difference
--------------------------------------------------------------------------------------
s     °    '                      s     °    '                
--------------------------------------------------------------------------------------
Sun                     7 - 23 - 08                    7 - 24 - 09            1° 1'
Moon                   5 - 24 - 07                    6 -  8 - 36             14° 29'
Mars                    7 - 27 - 58                    7 - 28 - 43            45'
Mercury               7 -  9 - 10                     7 - 10 - 41            1° 31'
Jupiter                 6 - 12 - 01                    6 - 12 - 12            11'
Venus                  7 - 13 - 46                    7 - 15 - 02           1° 16'
Saturn                 10-  1 - 20                   10-  1 - 24             4'
Rahu                   7 -  9 - 12                     7 -  9 - 14             2'
Ketu                    1 -  9 - 12                     1 -  9 - 14             2'


--------------------------------------------------------------------------------------

Calculation of Longitude of Sun

Now we would use the proportional logarithms tables provided in the Annual Ephemeris, 1993 in the end.  Horizontally, degrees or hours are given, and vertically, minutes are given.
As calculated above, speed of Sun comes to 1° 1'.

Log for 1° 1' (From the above Table)                     1.3730
Add log for the difference of 22 h 20 m                  0.0313
(Take horizontally 22 h and vertically 20', 
and see them meet at 0313)                                 1.4043

Now, search this figure (1.4043) in the above Table.  The nearest figure is 1.4025.  This is written at the cross-section of 0° 57'.  This means Sun has traveled 57' in 22 h 20'.

Longitude of Sun on 9.12.1993   7 s 23° 08' at 5.30 AM

Add the distance covered in    0 s 00° 57' 22 hr 20 m

Longitude of Sun at the given birth time       7s 24° 05'


Similarly, we can calculate for other planets

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