Thanks Therese,
Thats very helpful of you. Of course there are those that suggest Sri Yukteswar was not really proposing an astrological ayanamsa at all. Foremost amongst those is the astrologer Ernst Wilhelm.
Here is a quote apparently made by Ernst Wilhelm replying to a question on this:
''Sri Yuktesvar never used the ayanamsa named after him. When he wrote the Holy Science and talked about the Yugas he used Mean Motions of the precession, which is 24000 years, just like Manu Samhita uses the same mean motions. Talking in mean motions makes truth for all time. However, in this particular cycle, it will take 25600 years for the equinoxes to progress through the zodiac. And Sri Yuktesvar knew this of course as it was known during that time. He then goes on to say that the revati star marks the first point of sidereal aries, which is what the galactic center middle of mula ayanamsa comes to by the way. The then uses mean motions to arrive at a revati position that is not true from observation, but true from a mean motion point of view. Yuktesvar was not talking about precession in respect to
astrologers calculating an ayanamsa, but about mean motions of the great cycle. Readers did not understand this and so derived an ayanamsa based on mean motions in his book ? not what he intended. But that is the norm, people take wise words and do the unintentional with them.
Additionally, Tara Ma, a disciple of Yogananda who was very much into occult sciences and who Yogananda said that if he wanted to talk of metaphysical things and could not talk to Yuktesvar, his favorite person to talk to was Tara Ma. Tara Ma derived an ayanamsa based on the true motion of this period?s precession, 25600 years, and the actual position of Revati and in so doing came up with an ayanamsa very close to dhruva galactic center middle of Mula.
One thing that has to be kept in mind is that no star marks the ayanamsa. Ancients just used stars as reference points, Yukteswar actually said 10 mintues from Revati. But now that we have discovered the galactic center we can use what is actually fixed, the galactic center. NO stars are really fixed, they all move, decay, burn out, etc. Only the GC, the galactic center, will be here through the entirety of our galaxy?s existence. But the dhruva galactic center middle of Mula ayanamsa is marked by Revati, the star chosen by Sri Yuktesvar.?
Getting back to my comments above it would make more sense if the precessional cycle described by the Siddhantic astrologers coincided with the equinox at Revati (zeta Pisces rather than beta Aries. Otherwise it would mean these astronomers were unable to calculate the stars aligned to the vernal point!
This would require Revati to be considered the beginning of sidereal Aries rather than in sidereal Pisces. The problem is that that they indicate the cycle had returned to its starting point established in the Kali yuga with the vernal point at the beginning of Aswini and sidereal Aries. I dont think Revati has ever been linked to this nakshatra has it?

Its obviously, the 27th Nakshatra today and quite separate from Ashwini.
Pingree is quite clear the Siddhantic astronomers believed the chosen zero date was when the equinox point had returned to both the beginning of sidereal Aries and Ashwini. They simply disagreed what date this occurred.
This has led a few people such as Ernst Wilhelm to actually suggest the basic logic of the original 12 sign zodiac in India was really
tropical. In other words the zero point of 499CE , 522CE or 589CE coincided with when the Siddhantic astronomers thought that the two zodiacs coincided. If the outlook was not essentially tropical (or perhaps proto-tropical is more accurate due to their faulty understanding of precession) why concern themselves with aligning the zero point of their zodiac around the vernal point in the first place? Siderealists are usually keen to point out the astrology of India is fully sidereal and has no connection to seasonal considerations found in western astrology. Why then did the Siddhantic astronomers devote so much time and energy to seek a zero date which aligned their zero point with the vernal point? Logically, what interest has a fully sidereal astrology got with coinciding with the vernal point? Shouldn't such considerations have been totally irrelevant from a purely sidereal outlook?
I guess these comments will set the cat amongst the pigeons here! Anyone else have any thoughts on this?
One additional point. The Aryabhata of Aryabhata I is our main source for dating the beginning of the yuga. He states in the text that he was 23 years old at the time of composition of the text and dates his work from the time since the yuga began. Intriguingly the popular date for this text is 499CE! Another tradition claims it was written in 522 CE. Coincidence or what?
Also Aryabhata nowhere refers to the Kali yuga in his work. In fact the sequence of yugas he describes is the Jain sequence of yugas.
The 9th sloka in the 3rd chapter of Aryabhata states-
Utsarpini Yugartham Paschadapasarpini Yugardham cha
Madhye Yugasya sushama Adavante dushamenduchaat
This has been translated as: ''... the first half of a Yuga is Utsarpini and the second half is Apasarpini. Sushama is the middle of the Yuga and Dushama is the start and end of the Yuga. All the calculations related to Yuga must be done considering the Apogee of Moon.''
What is striking here is that terms like the
Utsarpini,
Apasarpini divisions of Yuga and the
Sushama,
Dushama middle divisions are not related to the Hindu system of time division, but a Jain system. The astronomer K Chandra Hari has written very convincingly on this topic. However, here is a more basic article discussing the issue:
http://jainology.blogspot.co.uk/2009/12 ... ose_button
This leads to two interesting conclusions. Firstly, Aryabhata was almost certainly a Jain and secondly the date used to calculate the beginning of the Kali Yuga by Hindus across the world from medieval times (The Aryabhata) is actually based on Jain cosmology! In medieval Hinduism the Vaishnavites seem to have appropriated this chronology as the assumed time when Sri Krishna ascended to heaven at the beginning of the Kali yuga.
Mark