Banū Mūsā

The Banū Mūsā brothers ("Sons of Moses"), namely Abū Jaʿfar Muḥammad ibn Mūsā ibn Shākir (before 803 – 873), Aḥmad ibn Mūsā ibn Shākir (803 – 873) and Al-Ḥasan ibn Mūsā ibn Shākir (810 – 873), were three 9th-century Persian scholars of Baghdad who are known for their Book of Ingenious Devices on automata (automatic machines) and mechanical devices.

The Banu Musa were sons of Mūsā ibn Shākir, who had been a highwayman and later an astrologer and astronomer to the Caliph al-Maʾmūn. After his death, his young sons were looked after by the court of al-Harun's son, the caliph al-Maʾmūn. 

The brothers were given access to the famous House of Wisdom library and translation center in Baghdad. They participated in the efforts to translate ancient Greek works into Arabic by sending for Greek texts from the Byzantines, paying large sums for their translation, and learning Greek themselves.

They were mathematicians, expanding on Appolonius' work by writing on the mathematics of ellipses and cones. They were astronomers, correctly calculating the circumference of the earth when asked to do so by al-Mamun. 

Most notable among their achievements is their work in the field of automation, which they utilized in toys and other entertaining creations. Their Book of Ingenious Devices describes 100 such inventions; the ones which have been reconstructed work as designed. While designed primarily for amusement purposes, they employ innovative engineering technologies such as one-way and two-way valves able to open and close by themselves, mechanical memories, devices to respond to feedback, and delays. Most of these devices were operated by water pressure.

Ahmad ibn Muhammad ibn Kathīr al-Farghānī

Abū al-ʿAbbās Aḥmad ibn Muḥammad ibn Kathīr al-Farghānī also known as Alfraganus in the West was a Persian astronomer and one of the famous astronomers in 9th century.

He was involved in the calculation of the diameter of the Earth by the measurement of the meridian arc length together with a team of scientists under the patronage of al-Ma'mūn in Baghdad. His textbook Elements of astronomy on the celestial motions, written about 833, was a competent descriptive summary of Ptolemy's Almagest. It was translated into Latin in the 12th century and remained very popular in Europe until the time of Regiomontanus. Dante Alighieri's knowledge of Ptolemaic astronomy, which is evident in his Divina Commedia as well as other works such as theConvivio, seems to have been drawn from his reading of Alfraganus.  In the 17th century the Dutch orientalist Jacob Golius published the Arabic text on the basis of a manuscript he had acquired in the Near East, with a new Latin translation and extensive notes.

Later he moved to Cairo, where he composed a treatise on the astrolabe around 856. There he also supervised the construction of the large Nilometer on the island of al-Rawda (in Old Cairo) in the year 861.

The crater Alfraganus on the Moon is named after him.

Abu Ma'shar al-Balkhi

Abū Maʿshar, Jaʿfar ibn Muḥammad al-Balkhī (also known as al-Falakī or Ibn Balkhī, Latinized as Albumasar, Albusar, or Albuxar) (10 August 787 in Balkh, Khurasan – 9 March 886 in Wāsiṭ, Iraq), was a Persian astrologer, astronomer, and Islamic philosopher, thought to be the greatest astrologer of the Abbasid court in Baghdad. He was not a major innovator, and his works are practical books for training of astrologers; even as an astrologer he was not intellectually rigorous. He wrote a number of practical manuals on astrology that profoundly influenced Muslim intellectual history and, through translations, that of western Europe and Byzantium.

Muḥammad ibn Mūsā al-Khwārizmī

Abū ʿAbdallāh Muḥammad ibn Mūsā al-Khwārizmī (c. 780, Khwārizm – c. 850) was a Persian mathematician, astronomer and geographer, a scholar in the House of Wisdom in Baghdad.

In the twelfth century, Latin translations of his work on the Indian numerals, introduced the decimal positional number system to the Western world His Compendious Book on Calculation by Completion and Balancing presented the first systematic solution of linear and quadratic equations in Arabic. In Renaissance Europe, he was considered the original inventor of algebra, although we now know that his work is based on older Indian or Greek sources  He revised Ptolemy's Geography and wrote on astronomy and astrology.

Some words reflect the importance of al-Khwarizmi's contributions to mathematics. "Algebra" is derived from al-jabr, one of the two operations he used to solve quadratic equations. Algorism and algorithm stem from Algoritmi, the Latin form of his name.  His name is also the origin of (Spanish) guarismo and of (Portuguese) algarismo, both meaning digit.

Naubakht

Nobakht Ahvazi (Persian: نوبخت اهوازى, (or Naubakht Ahvaz) also transliterated 'Naubakht') and his sons were astrologers from Ahvaz (in the present-day Khuzestan Province of Iran).

Nobakht was particularly famous for having led a group of astrologers who picked an auspicious electional chart for the founding of Baghdad. His family also helped design the city. Originally Zoroastrians,Nobakht and his sons converted to Islam and were employed as Pahlavi translators of the Abbasid court.