On June 6, 1436, German mathematician, astronomer, astrologer, translator, instrument maker and Catholic bishop Johannes Müller aus Königsberg was born, better known under the Latinized version of his name as Regiomontanus. His diligent and accurate observations, measurements and recordings paved the way for modern astronomers such as Tycho Brahe  and Nikolaus Copernicus.
Johanne Müller aus Königsberg grew up in a well situated family, and got in touch with astronomical calculations very early. Historical scientists assume, that he had already plenty ob knowledge at the age of 12. He then enrolled at the University of Vienna, which back then was one of the most important schools for mathematical and astronomical education. After graduating, Regiomontanus taught mathematics and philology. Major influences during his time in Vienna were the horoscopes he had to create for Frederick III. and his family as well as the humanism, of which he included elements in his lectures on planetary theories.
When cardinal Bessarion invited Regiomontanus to Rome, he finished to translate the famous Almagest by Ptolemy, wherefore his influence in Italy grew. The work became one of the most influential contemporary astronomical works used by Nikolaus Copernicus and Galileo Galilei.  In the following years, Regiomontanus accepted further scientific positions and published a few works on trigonometry as well as translated more works into Latin. In 1467, he was occupied with establishing astronomical panels wherefore he constructed his own instruments for observation. A few years later he also improved Jacob’s staff, an instrument helping to measure angles before the sextant was invented.
In 1471 he moved to Nuremberg on behalf of King Matthias in order to further improve the plates of the planetary movements there. Because of the flourishing instrument making and the good location he remained first as the king’s envoy, but later in his own decision. He now opened his own printing works in which he wanted to produce his tables in the best quality. In 1474 he published his publishing program as a single-sheet print; he could complete 11 prints, further publications thwarted his early death. In 1472 he published Peuerbach‘s ‘Theoricae novae Planetarum and Manilius‘ teaching poem Astronomica. The Ephemerides (Ephemerides quas vulgo vocant almanac, a projection of the daily movements of celestial bodies, conjunctions and eclipses over the following 32 years) for the years 1475 to 1506 were almost ready printed (“… iam prope absoluta sunt“), as his publishing program announced in 1474. This printed set of tables served Christopher Columbus on his voyages of discovery overseas.
In his following scientific works, Regiomontanus improved current works on planetary movements in Nuremberg. With his self built instruments, he was able to improve overall astronomical knowledge and intended to open printing works in order to publish his findings. But unfortunately his plan could not be realized before his early passing. Just before his death, Regiomontanus took part in the reformation of the calendar and published his famous work ‘Calendarismus‘ in 1476.
Only one year later he died (probably from an epidemic) at the age of only 40. According to Hartmann Schedel, he was buried on God’s Field (Ager dei), which probably means the Campo Santo Teutonico. However, according to legend, he was buried in the Pantheon. Regiomontanus is considered the most important mathematician (founder of modern trigonometry, among others) of his time and early reformer of the Julian calendar.
Regiomontanus was a typical representative of Renaissance humanism: in his opinion, his own observation and comparison with the results of ancient science (Aristotle) should renew astronomy and help to find “the truth”. With this attitude he became, along with Nikolaus von Kues, the essential pioneer of the Copernican worldview.
At yovisto academic video search, you may enjoy a video lecture by Chris Lintott explaining the History of the Universe in 12 Minutes at the University of Oxford.
References and Further Reading:
-  John J. O’Connor, Edmund F. Robertson: Regiomontanus. In: MacTutor History of Mathematics archive
-  Regiomontanus at Princeton
-  Regiomontanus at Sternwarte Nuremberg
-  Tycho Brahe – The Man with the Golden Nose, SciHi Blog
-  Nikolaus Copernicus and the Heliocentric Model, SciHi Blog
-  Basilios Bessarion and the Great Revival of Letters, SciHi Blog
-  Galileo Galilei and his Telescope, SciHi Blog
-  Regiomontanus at Wikidata