published in 1614 the Disquisitiones mathematicae in Ingolstadt with Johann Georg Locher, in 1615 Sol ellipticus in Augsburg and with Georg Schönberger Exegeses fundamentorum gnomonicorum in Ingolstadt, and in 1617 he published Refractiones coelestes, also in Ingolstadt. Scheiner took his remaining vows of poverty, chastity, obedience and loyalty before the Pope on 31 July 1617 in the town of Ingolstadt under Father Johannes Manhart S.J. In the very same year Scheiner made known his wish to go to China as a missionary. Father General Mutio Vitelleschi sent him a letter, however, telling Scheiner he had better stay in Europe and persevere with his mathematical studies. In the winter of 1617/1618, Scheiner returned to Innsbruck, Austria at the behest of Archduke Maximilian III. Innsbruck/Freiburg/Neisse: 1617–1624 After November 1614, Archduke Maximilian III summoned Scheiner to Innsbruck several times to discuss astronomical and mathematical questions. The Archduke had received an astronomical telescope with two convex lenses which showed objects upside down and the wrong way round. Scheiner added a third lens, thus manufacturing a terrestrial telescope which allowed Maximilian to see the beautiful stretches of his country while standing upright. A portable camera obscura was developed by Scheiner in Innsbruck. Furthermore, a walkable camera obscura was constructed. After the death of Maximilian III in 1618, Archduke Leopold V was appointed imperial representative of Tyrol and of the Upper Provinces. Like his predecessor Maximilian, Leopold V put his trust in Father Scheiner. Scheiner's "Oculus hoc est: Fundamentum opticum," containing many new insights into the physiological nature of the eye, was published in Innsbruck in 1619. The book had been written earlier in Ingolstadt. Oculus is subdivided into three parts: the first part treats the anatomy of the eye, the second part the refraction of the light ray inside the eye, and the third part deals with the retina and the visual angle. Scheiner once again chooses the way of observation and experiment. Like Kepler before him, he found that the retina is the seat of vision and that the optic nerve transmits the images from the retina to the brain. Scheiner was rebuked once more for going from Innsbruck to Hall in a heavily loaded coach drawn by six horses! Father General Vitelleschi wrote him a letter. Archduke Leopold V and Father Scheiner carried on a sizeable correspondence from 1620 until 1632. One of Scheiner's letters to Leopold from 1626 informs the Archduke that