Al-Battani
Arab astronomer and mathematician who made remarkably accurate astronomical observations and improved Ptolemy's star catalog.
Who or what
Abu Abd Allah Muhammad ibn Jabir ibn Sinan al-Battani (c. 858–929), known in the West as Albategnius, was an Arab astronomer and mathematician from Harran.
He made highly accurate observations over 41 years, determining the solar year length, precession of the equinoxes, and inclination of the ecliptic.
Why it mattered
Al-Battani's observations were so precise that they were used by Copernicus, Kepler, and Tycho Brahe centuries later.
He corrected many of Ptolemy's errors and provided the empirical basis for later European astronomy.
Key works and moments
He calculated the solar year as 365.24255 days (modern: 365.24219), accurate to within 0.00036 days (about 31 seconds).
He corrected the obliquity of the ecliptic from Ptolemy's 23\u00b051' to 23\u00b035' (modern: 23\u00b026').
Further detail
His major work, "Kitab al-Zij," contained 57 chapters covering astronomy, trigonometry, and astronomical instruments.
He introduced the use of sines and tangents in astronomical calculations, moving beyond Ptolemy's chord-based methods.
Legacy
His observational data became a cornerstone of European astronomy for 700 years.
Many European astronomers (Copernicus, Kepler, Galileo) relied on his tables and observations.
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