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Rashi Valaya Yantram In Hindu Astronomy

In the observatory at Jaipur, twelve instruments have been positioned and named after the twelve signs of the zodiac starting from Aries to Pisces. They are known as Rashi Valaya Yantrams in Hindu astronomy, from which the tropical longitudes of planets/stars and a sara can be ascertained.

When the tropical Aries point crosses the meridian passage time exactly (during day time), the shadow will fall on the degrees and minutes marked on the circle which will be the measure of the tropical sun. The degrees and minutes read from the shadow cast on this yantra is called chayark and in the Hindu ephemeris, the sun’s degrees and minutes reflected on this contrivance are called karnark. Karnark subtracted from chayark yields ayanamsha. Therefore the reading of ayanamsa every day can be correctly gauged with this instrument.

A recently built observatory (1992) at Sampurnanand University, Varanasi, has two such yantras – the karkarasi valaya yantra and the makarrasi valaya yantra. From the former instrument, when the first point of karka rashi (cancer) or the 91st degree of the zodiac passes through the meridian, the tropical longitude of the star/planet can be ascertained. Similarly, from the latter, when the first point of Makara (Capricorn) rashi crosses the meridian, the tropical longitude of the star/planet can be obtained.

In Delhi, Shri L B S National Sanskrit Vidyapeeth uses the Karka, the Makara, and the Tula Rashi (Cancer, Capricorn and Libra) valaya yantras, which at any observation time will indicate the tropical longitude of any star/planet every day.