 This value was improved by 28s, 88 years later in 1525 by Nicolaus Copernicus (1473–1543), who appealed to the estimation of Thabit ibn Qurra (826–901), which was accurate to +2s.However, Ulugh Beg later measured another more precise value as 365d 6h 9m 35s, which has an error of +25s, making it more accurate than Copernicus' estimate which had an error of +30s.Ulugh Beg also determined the Earth's axial tilt as 23;30,17 degrees in sexagesimal notation, which in decimal notation converts to 23.5047 degrees.