Astronomers select Baghdad's foundation date

Modern calculations verify an eclipse, while the prediction narrative must be treated more cautiously than the astronomical date.

The parameters of the Aryabhatiya are reckoned for mean noon at Ujjain on 21 March 499, providing a precise base date for calculations.

Aryabhata gave procedures for planetary positions, eclipses and time using concise Sanskrit verse.

Aryabhata compared the daily westward movement of stars with apparent motion experienced from a moving boat.

His trigonometric methods enabled quantitative work on arcs, shadows, eclipses and celestial coordinates.

Celestial calculation helped legitimize an imperial city and demonstrates the close historical relationship between astronomy and astrology.

The planners' backgrounds reflect the multilingual and multireligious networks that later supported scholarship in Baghdad.

The city developed institutions where Indian, Persian and Greek materials were translated, criticized and extended in Arabic.

A new star appeared around 30 April–1 May and was recorded from East Asia and the Islamic world to Europe and possibly beyond.

His description included brightness, position and atmospheric effects, providing important evidence from Arabic astronomy.