Christoph Scheiner (25 July 1573 NS - 18 July 1650 NS) was a German Jesuit priest, mathematician, and astronomer best known for his telescopic observations of sunspots and his extended priority dispute with Galileo Galilei over their discovery. Scheiner made significant contributions to optics, astronomy, and the physiology of human vision, and his major work Rosa Ursina sive Sol (1626-1630) remained a standard reference on solar observation for over a century.

Scheiner was born in Wald, in the Swabian region of the Holy Roman Empire, and entered the Society of Jesus in 1595. He studied and later taught mathematics and Hebrew at Ingolstadt, where he constructed a pantograph - a mechanical drawing instrument - and conducted early experiments in optics. Around 1611, he began systematic telescopic observation of the Sun, initially using smoked glass filters and later projection methods he helped develop. His sunspot observations were communicated pseudonymously in letters to the Augsburg banker and patron Marcus Welser, published as Tres Epistolae (1612) under the name “Apelles latens post tabulam” - a caution likely reflecting both Jesuit institutional constraints and the contested nature of the observations.

Galileo responded to Scheiner's letters with his own Letters on Sunspots (1613), asserting prior discovery and arguing - correctly, as later consensus would hold - that sunspots were features on or near the solar surface rather than small planets transiting the Sun, as Scheiner initially proposed. The dispute over priority and interpretation became entangled with the broader conflict over heliocentrism and contributed to lasting personal animosity between the two men. Some historians regard Scheiner's testimony and influence as a factor in the 1633 trial of Galileo, though the extent of his role remains debated. See Christoph Scheiner - History for a fuller account.

Scheiner's later work, Oculus hoc est: Fundamentum Opticum (1619), offered an early and detailed account of the optics of the human eye, including the role of the retina in image formation. Rosa Ursina, his most comprehensive astronomical work, provided extensive data on sunspot positions, solar rotation, and the inclination of the solar axis - data that remained useful to later astronomers regardless of the priority controversy.

There is broad astronomical consensus that sunspots are solar phenomena, not planetary transits, consistent with Galileo's position against Scheiner's early interpretation. Historical consensus on the priority question is less settled; most historians credit both men with independent, roughly contemporaneous observations, with Galileo having published first in the form most influential to subsequent science. See Heliocentrism and Galileo for related consensus discussion.

• Scheiner as independent co-discoverer - Some historians argue Scheiner's systematic methods and long-term solar data collection represent a contribution equal to or exceeding Galileo's, independent of the priority dispute. Viewpoint: Independent Co-Discoverer
• Scheiner as adversary to Galileo - The traditional historiographical framing casts Scheiner as an antagonist whose Jesuit institutional loyalties and personal rivalry contributed to Galileo's condemnation. Viewpoint: Adversary to Galileo
• Scheiner's contributions undervalued - A revisionist position holds that Scheiner's optical and solar work has been systematically underappreciated due to his association with the losing side of the heliocentrism controversy. Viewpoint: Contributions Undervalued

• Christoph Scheiner - History
• Heliocentrism and Galileo
• Sunspots
• Galileo Galilei
• Rosa Ursina sive Sol
• Sunspots - Astronomy Consensus
• Society of Jesus and Science

1. Daxecker, Franz. The Physicist and Astronomer Christopher Scheiner: Biography, Letters, Works. Innsbruck: Universitätsverlag Wagner, 2004.
2. Reeves, Eileen, and Albert Van Helden, trans. and eds. On Sunspots: Galileo Galilei and Christoph Scheiner. Chicago: University of Chicago Press, 2010.
3. Van Helden, Albert. “Galileo and Scheiner on Sunspots: A Case Study in the Visual Language of Astronomy.” Proceedings of the American Philosophical Society 140, no. 3 (1996): 358-396.
4. Scheiner, Christoph. Rosa Ursina sive Sol. Bracciano: Andreas Phaeus, 1626-1630.
5. Galilei, Galileo. Istoria e dimostrazioni intorno alle macchie solari. Rome: Giacomo Mascardi, 1613.
6. Lindberg, David C., and Ronald L. Numbers, eds. God and Nature: Historical Essays on the Encounter between Christianity and Science. Berkeley: University of California Press, 1986. Ch. 4.