Achyutha Pisharodi (c. 1550 at Trikkandiyur, Tirur, Kerala, India – 7 July 1621 in Kerala) was a Sanskrit grammarian, astrologer, astronomer and mathematician who studied under Jyeṣṭhadeva and was a member of Madhava of Sangamagrama's Kerala school of astronomy and mathematics. He is remembered mainly for his part in the composition of his student Melpathur Narayana Bhattathiri's devotional poem, Narayaneeyam.
He discovered the techniques of 'the reduction of the ecliptic'. He authored Sphuta-nirnaya, Raasi-gola-sphuta-neeti (raasi meaning zodiac, gola meaning sphere and neeti roughly meaning rule), Karanottama (1593) and a four- chapter treatise Uparagakriyakrama on lunar and solar eclipses.
- An introduction to Sanskrit grammar.
- Astronomical work dealing with the computation of the mean and true longitudes of the planets, with eclipses, and with the vyatūpātas of the sun and moon.
- Uparāgakriyākrama (1593)
- Treatise on lunar and solar eclipses.
- Astronomical text.
- Astronomical text.
- Manual on the computation of eclipses.
- Work concerned with the reduction of the moon’s true longitude in its own orbit to the ecliptic.
- An adaptation of the Jātakapaddhati of Śrīpati.
Pisharati is known to have scolded and provoked an errant Narayana to take up the Brahmin's duties of prayer and religious practices. He accepted Narayana as his student. Later when Pisharati was struck with paralysis (or rheumatism by another account), Narayana, unable to bear the pain of his dear guru, by way of Gurudakshina took the disease upon himself. As a result Pisharati is said to have been cured, but no medicine could cure Narayana. As a last resort, Narayana went to Guruvayur and requested Thunchaththu Ramanujan Ezhuthachan, a great devotee of Guruvayoorappan, to suggest a remedy for his disease. Ramajunan Ezhuthachan advised him to compose a poetical work on the Avatars (incarnations) of Lord Vishnu beginning with that of Matsya (Fish). Narayana composed beautiful slokas in praise of Lord Guruvayurappan and recited them before the deity. He was soon cured of his disease.
The book of slokas written by Narayana were named Narayaneeyam. The day on which Narayana dedicated his Narayaneeyam to Sri Guruvayurappan is celebrated as "Narayaneeyam Dinam" every year at Guruvayur.
- David Pingree. "Acyuta Piṣāraṭi". Dictionary of Scientific Biography.
- S. Venkitasubramonia Iyer. "Acyuta Piṣāroṭi; His Date and Works" in JOR Madras', 22 (1952–1953), 40–46.
- K. Kunjunni Raja. The Contribution of Kerala ot Sanskrit Literature (Madras, 1958), pp. 122–125.
- ---- "Astronomy and Mathematics in Kerala" in Brahmavidyā, 27 (1963), 158–162.