There’s a naksatra every 13 and a third degrees. So all you need to know is the starting point and you can measure where the naksatra are in the sky. The starting point is 180 degrees opposite the main star of Citra nakshatra (Spica). Where this coincides with tropical space changes over the course of history because the stellar and equitorial/ tropical measurements of a “year” differ by 20 minutes per year. So, the stars drift through the 12 signs. The 12 signs are divisions of the sun’s path (‘ecliptic’) the stars also move against the ecliptic like the planets, but at a massively slower rate. About 5000 years ago, what we now consider the 3rd naksatra (Kṛttikā) was considered the 1st (in Ṛg and Atharva Veda, for example) because it aligned roughly with the beginning of the 1st division of the ecliptic, Aries. A little less than 2000 years ago what is commonly still thought of as the “1st” nakṣatra was Aśvinī, because it aligned with the 1st division of the ecliptic at the time. From that time things got confusing and astrologers/astronomers didn’t want to continue to update the position of the nakṣatras in reference to the position of the ecliptic divisions (rāśi). That’s why many people practicing Indian astrology still count Aśvinī as the 1st nakṣatra and even start the ecliptic divisions from the start of Aśvinī, creating a “sidereal zodiac.” However, the accurate fact is that currently the main star of Citrā (Spica) is 180 degrees opposite from just shy of 24 degrees Aries.
Thus if we wanted to restart the ancient, accurate method of reviewing the status of ‘1st nakshatra’ we would make Pūrva-bhādrapadā, beacause that nakshatra is now the one roughly aligned with the start of the first division of the ecliptic.
Anyway, its less confusing to start from 24 Aries, and measure 13 and a third degrees for each naksatra – that’s how you can know where each one currently is, plus or minus a handful of minutes of arc, since the start is still a little shy of 24 Aries in truth. So for example Aśvinī corresponds to 24 aries through 7:20 of Taurus. Bharanī from 7:20 Taurus to 20:40 Taurus. Kṛttika from 20:40 Taurus to 4 Gemini. Rohini from 4 Gemini to 17:20 Gemini, etc.
This is the current corrlation of nakṣatra to rāśi. In a century or two the drift would be significant enough that you would want to update the measurement.
Vic DiCara's Astrology 