Thursday, June 09, 2005

Calculations in JHora

Dear Members,

I have some questions regarding Jhora 7.02 (full 57 mb version) :

Why is there a difference in arc seconds/minute between Jhora
7.02 and Swiss Ephemeris ?

Using planetary positions on 1st of Jan 2005, 00:00 hr, GMT
+00:00, Lahiri, as an example :

Jhora = Sun 16:44:50.83
Swiss = Sun 16:44:28.6793

Jhora = Moon 15:22:12.37
Swiss = Moon 15:22:09.7656

Jhora = Mars 10:26:02.53
Swiss = Mars 10:25:29.0106

Jhora = Mercury 24:29:01.41
Swiss = Mercury 24:28:35.4791

Jhora = Jupiter 23:21:58.32
Swiss = Jupiter 23:21:46.2340

Jhora = Venus 25:11:12.33
Swiss = Venus 25:10:30.8806

Jhora = Saturn 01:00:07.95
Swiss = Saturn 01:00:19.9033

Correct me if I am wrong, both software is using exactly the same
ephemeris file "sepl_18.se1" to generate these planetary positions.

If that is the case, shouldn't the figures be exactly the same or at
least the same after rounding off the arc second decimal places ?

This is not an attempt to put Jhora in bad light, but a serious
desire to find out why the difference in the figures.

I use Jhora frequently and I am very grateful to Narasimha for not
only releasing such a fine software free of charge but also uploading
the full 57 mb version for the public to download.

Thanks in advance to any reply to my above-mentioned queries.

Best Wishes,

Namaste Pushya,

I am away from the lists. If anybody has something urgent that needs my
attention, they should cc the mail to me. Sanjay, thank you for forwarding
the mail to me!

The Swiss Ephemeris positions you gave must have been computed using
"apparent" positions instead of "true" positions. In JHora, select
"Preferences", then "Related to calculations" and then "Planet Calculation
Options". In JHora, default is "true" positions. So you are comparing apples
to oranges. If you want to compare apples to apples, please change the JHora
option to use apparent positions (though I recommend true positions).

If you change the option and do a comparison, you will no longer have upto
30 arc-sec differences that you showed below. The differences will be more
or less uniform and will be slightly less than 2 arc-sec.

Apart from small differences in rounding, that 2 arc-sec difference is
largely due to differences in ayanamsa calculation. I use Swiss Ephemeris
only for tropical planetary positions and do not use their sidereal
calculations. I use my own module to compute the ayanamsa. There is a small
difference between what they do and what I do.

The original Lahiri ayanamsa was linear - it assumed a fixed rate of
precession. However, linear ayanamsa is not correct. Science does not know
the correct ayanamsa, but we do know the correct model for the changes in
ayanamsa with time (given the initial ayanamsa on a particular date and
time). So I use the non-linear model. I am assuming that Swiss Ephemeris
uses the original linear Lahiri ayanamsa OR, more likely, they use the
correct non-linear model, but use a slightly different seed. In other words,
they and I may have converted the linear ayanamsa into a non-linear one in a
slightly different way. When we non-linearize Lahiri ayanamsa, should we
take the star position as sacrosant or the zero ayanamsa date given by
Lahiri to be sacrosanct or the ayanamsa value given for some specific date
(e.g. 1900 Jan 1) as sacrosanct? We can't honor all of them and have to
honor only one of them. If you assume a linear ayanamsa change rate as
Lahiri originally did, all of them can be honored. But, when we
non-linearize it, we have to choose one of them, honor it and deviate in the

In any case, I will investigate this further and correct any errors in my
software or give new options if I deem them appropriate.

On a separate note, some people have been asking me to allow linear
ayanamsas. For example, Yukteshwar ayanamsa uses a fixed rate of precession
change that is factually known to be wrong. However, it looks like some
people want to stick to it. In future, I will add support for some linear
ayanamsas also (though they are definitely wrong).

I hope this answers your question. But, by using the same setting for
apparent/true positions in both softwares, you can considerably reduce the

Sanjay, you can rely on JHora for your ardha-nadi work, but please realize
that there are several options and make sure that you set them correctly. If
you have the patience to try all permutations and combinations, please try
them all and draw your own conclusions. Otherwise, I will suggest setting
"geocentric" positions, "true" positions and "mean" nodes in the "Planet
Calculation Options". However, I am not sure if Lahiri ayanamsa is fully
correct. Above, we were talking about deviations of 1-2 arc-sec between
softwares. But I am of the opinion that the Lahiri ayanamsa may be off by
1-2 arc-MIN. As this is comparable to the ardha-nadi size, your research
cannot be done without fixing the ayanamsa perfectly!

May Jupiter's light shine on us,

Jaya Jagannatha
Dear Narasimha
OK your point is made. We had also discussed this some time back and from next year shall start addresing the vexed ayanamsa issue so that we can at least try to settle it to whatever extent possible.
The options I have been using are -
1. Geocentric positions
2. True positions for planets
3. Mean nodes [still cannot understand why some people use true nodes ignoring Parasara and Jaimini's teaching of constant Rahu retrogression which is also confirmed in Prasna Marga rahu-sun-moon chakra and Jataka Parijatha]
4. Thanks for the poit on the need to tinker with the Lahiri Ayanamsa by 1-2 arc-min
Here is some point for you to consider in future
Case-1: Jiddu Krishnamurti
Krishnamurti, Jiddu
Date: May 12, 1895
Time: 12:23:30 am
Time Zone: 5:30:00 (East of GMT)
Place: 78 E 30' 00", 13 N 33' 00"
Madanapalle, India
Lagna in Swadhaa nadiamsa and Saturn exalted [male birth confirmation] is the ardha nadiamsa ruler confirming his beliefs on guru-shisya concept and his rejection of father [Saturn opposite Sun], his concept on total freedom [exalted in Libra and retro] etc. Now this can get altered if the *Custom Ayanamsa* is more than lahiri ayanamsa by 1m47sec to Venus which is completely wrong. So the upper limit of change is 1m46s > Lahiri > 2m0s ...........[A]

Case-2: Dr B V Raman
Raman, Bangalore Venkata
Date: August 8, 1912
Time: 7:43:00 pm
Time Zone: 5:30:00 (East of GMT)
Place: 77 E 35' 00", 12 N 59' 00"
Lagna in Navanita nadiamsa and Sun in Cancer [male birth confirmation] is the ardha nadiamsa ruler confirming his indept study as a jyotishi etc. Themodification does not occur if the change of *custom ayanamsa is within 2m0s >Lahiri> 1m57s...[B]
Taking A & B we have the range of 1m46s > Lahiri > 1m57s

Lot more cases have to be done before we can arrive at the exact ayanamsa.
I fully support your stand on the non-linear ayanamsa as this is closer to the truth and the liear ayanamsa has to be rejected sooner or later by all as it is a hangover of the past. As the worlds mathematical knowledge improves, astrologers must grow to benefit from it. Now come to the three options -
You state:
>When we non-linearize Lahiri ayanamsa, should we take the star
>position as sacrosant or the zero ayanamsa date given by
>Lahiri to be sacrosanct or the ayanamsa value given for some
>specific date (e.g. 1900 Jan 1) as sacrosanct?

1. Taking the star position to be sacrosanct - this is the chitra paksha definition and should be recommended by us (SJC) based on the first day of every century i.e. 1 Jan 1900 at midnight in Ujjain and 1 Jan 2000 etc and non-linear ayanamsa progression.
2. Zero ayanamsa date given by Lahiri - this should be called Lahiri Non-linear ayanamsa
3. There should be an option for Lahiri linear ayanamsa [we can never recommend this] for those who cannot understand why.
4. Forget any magic dates.

Add these options only when you have the time after the TP book. Now I have done some work recently on a chart using the sixth level of the Vimsottari dasa to prove to him that it works. Hari was visiting and here was my detailed reading.
Here are some extracts. Hari can copy the various mails he has been writing to Visti and others on this.

I can't recollect what Sanjay did with the rasi & navamsa as I was talking simultaneously with Sarbani at that time but nevertheless here is the table of events with comments by Sanjay that may help you to understand what Sanjay did with the rasi and navamsa.
Präëa antardaçä Deha antardaçä Reading of situation
Ra Me Left home to travel by flight in northern direction from Mumbai to Delhi
Ke Flight delayed due to technical reason
Ve Flight took off for Delhi
Mo Work of proof reading book given by Sanjay
Ju Ju Discussions with Sarbani, Freedom & Sanjay
Sa Very tired, went to sleep
Ke Woke up but did not get up from bed*
Ve Got up finally, attended interview
Mo Ate food but did not like it, offer of job and reimbursement of travel allowance (in FULL due to breaking of sakata yoga causing mukuta yoga)
Ma/Ra Discussions with Sarbani/Freedom/Sanjay
Sa Sa Left Gangaram hospital road residence to travel in west direction back to Mumbai. No boarding pass issued but after some time, issued boarding pass in first class although ticket was economy class
Data for use is:

Hari (rectified Sanjay Rath)

Natal Chart

Date: September 28, 1971
Time: 11:02:21
Time Zone: 5:30:00 (East of GMT)
Place: 80 E 14' 00", 13 N 02' 00"
Chennai Thyagarayanagar, India
Lahiri ayanamsa and apparent time of sunrise
Rath: * things like this were read from the rasi and navamsa using sixth level of vimsottari dasa to correct the time. He actually confirmed this later. The point is that this does not match the ardha nadiamsa of Saturn which is totally incorrect and the correct ardha nadiamsa ruler should be Venus which is (1) debilitated (F) conjoined (2) Sun (M) and (3) exalted (M) Mercury (M) to indicate a male [3M 1F] male birth.
Now what we need is the exact ayanamsa which gives this level of vimsottari dasa as indicated above and also Venus as the ardha nadiamsa ruler.
With best wishes and warm regards,
Sanjay Rath

Brihaspati Gayatri, Vishwamitra/Gaathina Rishi Rig Veda 6.62.6