Roger of Hereford was a medieval astronomer active at Hereford

Hereford

Hereford is a cathedral city, civil parish and county town of Herefordshire, England. It lies on the River Wye, approximately east of the border with Wales, southwest of Worcester, and northwest of Gloucester...

 in the period 1178 to 1198.

Nothing is known of Roger's nationality or when he was born nor of his education. He first appears in the historical record in 1176, when he wrote a computus

Computus

Computus is the calculation of the date of Easter in the Christian calendar. The name has been used for this procedure since the early Middle Ages, as it was one of the most important computations of the age....

, a treatise on calculating ecclesiastical dates for Gilbert Foliot

Gilbert Foliot

Gilbert Foliot was a medieval English monk and prelate, successively Abbot of Gloucester, Bishop of Hereford and Bishop of London. Born to an ecclesiastical family, he became a monk at Cluny Abbey in France at about the age of twenty...

, who had previously been Bishop of Hereford

Bishop of Hereford

The Bishop of Hereford is the Ordinary of the Church of England Diocese of Hereford in the Province of Canterbury.The see is in the City of Hereford where the seat is located at the Cathedral Church of Saint Mary and Saint Ethelbert which was founded as a cathedral in 676.The Bishop's residence is...

 but was at that time Bishop of London

Bishop of London

The Bishop of London is the ordinary of the Church of England Diocese of London in the Province of Canterbury.The diocese covers 458 km² of 17 boroughs of Greater London north of the River Thames and a small part of the County of Surrey...

. In this computus, Roger criticized the work of Gerland

Gerland (mathematician)

Gerland was an 11th-century mathematician who flourished in England following the Norman Conquest. Little is known of his personal life. His treatise on the Computus may be found in the British Museum and his work on the abacus is preserved in the Bibliothèque nationale de France in Paris....

, which was the standard work at the time on calculating ecclesiastical dates, and drew on Hebrew and Arabic learning.

Roger's connections with Hereford are shown by the fact that he wrote a set of tables showing the meridian of Hereford in 1178. He is probably the same person as the Roger Infans who was a witness on charters at Hereford in the time frame 1186 to 1198.

Another work of Roger's was an astronomical treatise covering most aspects of the subject. Entitled Liber de Quatuor Partibus Judiciorum Astronomie, it drew on earlier works by Raimond de Marseille, and the translations of Arabic works performed by Juan de Sevilla and Hermann of Carinthia. Besides the above works, manuscripts assign works on astrology and alchemy to Roger, although these works do not survive.

Roger was the dedicatee of a translation made by Alfred of Shareshill. Roger may also be responsible for a new method of calculating horoscopes.

Roger was an important scholar in transmitting the knowledge of Adelard of Bath

Adelard of Bath

Adelard of Bath was a 12th century English scholar. He is known both for his original works and for translating many important Greek and Arabic scientific works of astrology, astronomy, philosophy and mathematics into Latin from Arabic versions, which were then introduced to Western Europe...

 and others of a previous generation to a new generation of scholars, including Robert Grosseteste

Robert Grosseteste

Robert Grosseteste or Grossetete was an English statesman, scholastic philosopher, theologian and Bishop of Lincoln. He was born of humble parents at Stradbroke in Suffolk. A.C...

, who was a young member of the same household with Roger during Roger's later years at Hereford.