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 anticlockwise. 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, monthwise,
daywise, 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
crosssection 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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Way to cast a
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