Recently I’ve been asked which Ayanamśa or Ephemeris I use for examining charts, and seek to with this article to clarify what I’ve learned, what I use and what I don’t use and why.
My learning
From the beginning of my study of Vedic Astrology, I’ve used Chitra Paksha Ayanamśa, a.k.a. Lahiri Ephemeris. My Guruji, Pt. Sanjay Rath, has used the same throughout his teachings and I have used this as well. Pt. Rath still uses the same Chitra Pakṣa Ayanamśa, fine-tuned to the exact position of the fixed star, Spica, a.k.a. the Yoga Tārā of Chitra.
What about Lahiri (Chitra-Paksha)?
Lahiri’s Ephemeris, established through the Calendar Reform Committee of 1955, also sought to follow this position of Spica, however, adopted a formula which only worked for a temporary period of time and today is no longer in line with Chitra Paksha. To avoid making new formulas, as we have ready highly-accurate ephemeris-data from the Jet propulsion Laboratory of NASA, software makers have through the Swiss Ephemeris been able to mark and adjust the Ayanamśa to the exact longitude of Spica.
Popular astrology software such as Jagannātha Horā and Shri Jyoti Star have an option to chose Chitra Paksha Ayanamsha based on the exact position of the fixed star-Spica.
Why Spica?
The Calendar Reform Committee sought to follow the guidance of the Sūrya Siddhānta, which states that the star Spica (Chitra) is placed at 0 degrees of Libra. Hence the tern ‘Chitra-Paksha’, where paksha refers to that which is opposite, or 180 degrees away. This is from the concept of one paksha consisting of half a month or 15 Tithi – thus if one month is a 360 movement of the Moon, then half of it is 180 degrees.
The same advice of Sūrya Siddhānta is why I don’t use the Western Tropical Zodiac in general horoscopy.
Why not the SSS Ayanamsha?
The SSS model (termed Sūrya Siddhānta Ayanamsha) of calculating the planetary positions, presented in 2006, has arisen out of an inability to find concordance between the calculations presented in the Sūrya Siddhānta, and that of the observable planetary positions. The author, Vinay Jha, concludes herein, that the positions depicted in the Sūrya Siddhānta do not depict the planet’s positions, but that of their deities or divine attributes, and are thus not visible by observation.
A very bold statement which is subject to belief alone in that the calculations presented do in fact depict the deities positions and are dependent on the ability of the astrologer to accurately predict with these calculations.
Well, why not?
To this question we depend on books, as a statement delivered on faith should be met with the authorities we place our faith in. The text Horā Ratnam quotes several authorities on astrology as follows:


One could argue that the phrase ‘actual observations’ refers to those with the divine visions to see the deities actual positions, however, this statement (also repeated in Sūrya Siddhānta) points out the use of instruments or equipment for measurement.

One could lastly argue that these instruments are divine telescopes, but this author is yet to find a reference to the means of concocting such tools.
Concluding remarks
When learning astrology, my teacher taught how to worship the planets upon observation in the night-sky. A practice also used by many non-hindu civilizations such as the Mayans, Egyptians, Babylonians and possibly Celtic as well. To this day we practice examining the night sky to differentiate between the stars and planets using but our physical eyes. A tradition my teacher belongs to and has survived for at least 400 years.
The same Orissa tradition produced names such as Samanta Chandrasekhar, astronomer and author of Siddhant Darpan, whom with the use of Bamboo sticks would observe the planetary positions and could calculate these positions very accurately. To this illustrious tradition of Orissa I belong and look forward to sharing more knowledge from.