Johann Müller (the astronomer)

Today we have a curious trick: there are two Johann Müllers - both scientists, and both Catholics!

First, let us hear about Johann Müller, the astronomer - who was also called Regiomontanus.

He was one of the greatest of pioneers in modern astronomical knowledge. It was Regiomontanus's calendars that were used by the Spanish and Portuguese navigators in making their great voyages of discovery. Almost beyond doubt Columbus had ~ copy of these when he made his famous prophecy of the occurrence of an eclipse of the moon which so impressed the American Indians when they began to be impatient of the exactions of some of the members of the expedition and threatened to bring them no more supplies, and to cause other difficulties for them. Regiomontanus's career as a scientist was capped by his being invited to Rome in order to correct the Calendar, and by his elevation to the dignity of Bishop of Ratisbon, a successor after two hundred years of Albertus Magnus in that See, because the Pope was so impressed with his piety and learning.

...Johann Müller was born in 1436, and died in 1476, when he was just past forty years of age,— another striking proof that it is not the timeelement in work so much as the intensity factor that counts for accomplishment. During this brief life span he had revolutionized the study of astronomy, he had finished a work on trigonometry in which he introduced the use of tangents, had made all the calculations necessary to reform the calendar, and had begun the publication of a series of astronomical observations which were eminently helpful to all the students of his age. These observations were continued after his death; for, the initial difficulty being surmounted, the continuation was easy. They formed a precious incentive as well as a valuable guide to the astronomers of the next century. Yet all his life had not been devoted to astronomy: he had made his theological studies with great success; he had been ordained a clergyman; he had been especially successful in his studies in Greek literature and language, and had applied this knowledge to studying out what the ancients had learned about science; and yet, with all this he had been so faithful to his clerical duties that he was selected as the Bishop of Ratisbon.

...

It is easy to understand that, with the extremely imperfect instruments which they possessed at the time — often, indeed, they had to construct their own — this must have seemed an almost impossible problem. The telescope was not invented until nearly two centuries later; yet these devoted students, in spite of their handicap, were able to accomplish much that was valuable. As a result of his deep interest in astronomy, Müller devoted himself to the study of Ptolemy's works. The fact that they were written in Greek made them difficult in those times. Constantinople had fallen only a few years before; and while the Greek scholars from that city who were wandering in Italy were beginning to create that furore which was to be the characteristic of the Renaissance, it is easy to understand that their influence had not penetrated as far as Vienna. The fact that Müller successfully learned Greek shows that, even before the fall of Constantinople, the European universities, or at least scholars in many parts of Europe, had been waking up to the beauties and the treasures contained in the Greek language and literature.

...

It was because of his publications, however, that Müller (or Regiomontanus, as I suppose he should be called in connexion with these, for it is to them he owes the Latin form of his name) attracted the attention of not only astronomical students and observers, but also navigators, geographers, and practically all those interested in physical science, not to say the educated classes generally. He seems to have appreciated the value of publicity as an incentive to scientific work. The making of observations might be an intense pleasure for the observer; but if these were to be useful to other students and to mankind, they must be published, though publication involved an immense amount of trouble. Regiomontanus was tireless in bringing out calendars and ephemerides. Contrary to the customs of the time, these were not printed exclusively in Latin but there were also popular editions in German; and these are probably the first scientific works ever published in the German vernacular.

...

It was during the months spent in Rome that Müller commended himself so much to the Pope for his piety and his scholarship that he was selected as the Bishop of Ratisbon. Just about two centuries before, another great teacher and investigator in physical science, Albertus Magnus, had been made bishop of this same see. The three centuries from the birth of the first of these two men to the death of the second, represent the time when the Church was supremely dominant in European education. It is illuminating, then, to find that in the thirteenth and fifteenth centuries scientific scholarship of the profoundest kind, with devotion to scientific investigation that has never been surpassed, was not only no bar to ecclesiastical preferment, but was evidently even an added reason why the respective Popes of those periods selected these two great Bishops of the See of Ratisbon. Nothing that I know of is a more complete answer to the assertions of historians who insist on Church opposition to science during the Middle Ages, than this conjunction of Albertus Magnus and Regiomontanus as brother bishops of the same see, with two centuries of interval.

[From Walsh, Catholic Churchmen in Science, Second Series]

Also see the entry from the Catholic Encyclopedia.