How did Galileo Galilei and Christoph Scheiner contribute to observations of sunspots?

Galileo Galilei and Christoph Scheiner were among the first astronomers to conduct systematic telescopic observations of sunspots beginning around 1611. Their work was instrumental in moving beyond ancient naked-eye records to a scientific understanding of these solar features.12

Their contributions were marked by a notable scientific debate regarding the nature of the spots:

• Galileo Galilei: As an independent discoverer of sunspots, Galileo argued that they were located on or near the surface of the Sun. He supported his conclusions with a series of detailed engravings of his observations, which he published in his 1613 work, Istoria e dimostrazioni intorno alle macchie solari e loro accidenti (Letters on Sunspots).3
• Christoph Scheiner: A German Jesuit and mathematician, Scheiner initially argued that sunspots were satellites of the Sun, a position he took in an effort to preserve the then-prevailing belief in the perfection of the heavens. However, his later work, Rosa Ursina, contained drawings of sunspots of such high quality that they remained the standard for solar imaging until the early 20th century.32