Johannes Campanus (in Italian, Giovanni Campano) (1220–1296), also known as Campanus of Novara or similar, was an Italian astrologer, astronomer, and mathematician who devised a house system for the horoscope which bears his name. This house system divides the prime vertical into equal 30° arcs, or houses.
Born in Novara, he served as chaplain to Pope Urban IV and personal physician to Pope Boniface VIII. He travelled to Arabia and Spain.
In 1260, Campanus published a Latin edition of Euclid's Elementa geometriae, in fifteen books. The work was based on an Arabic translation of the original Greek text. Campanus probably also had access to the Latin translation of Euclid's work executed around 1120 by Adelard of Bath. It was used for two centuries and was printed in Venice in 1482 as Preclarissimus liber elementorum Euclidis.
In the field of astronomy, he wrote a Theorica Planetarum in which he geometrically described the motions of the planets as well as their longitude. He also included instructions on building a planetarium as well as its geometrical description. This was the first description of a planetarium by a European. Campanus also attempted to determine the time of each planet's retrograde motion. The data on planets are drawn from the Almagest and the Toledan Tables of the Arab astronomer Arzachel. Campanus gave precise instructions on using the tables, and made detailed calculations of the distances to the planets and their sizes.
Campanus also wrote Tractatus de Sphaera, De computo ecclesiastico and Calendarium.
His De computo ecclesiastico or Computus maior (ca. 1261 – ca. 1264) was written by Campanus for Pope Urban VI does not make any reference to a mechanical clock, thereby leading historians to believe that the clock was not invented until 1280 or so.
His contemporary Roger Bacon cited Campanus as one of the great mathematicians of the age.
He died at Viterbo.
The crater Campanus on the Moon is named after him.
* Campanus of Novara