A recent study by Japanese and Belgian astronomers has solved a historical mystery about solar cycles by re-examining sunspot drawings made by Johannes Kepler in the 17th century. The debate about who first observed sunspots dates back to ancient Chinese astronomers in 364 BCE, and mistaken interpretations continued for centuries. Kepler, Thomas Harriot, and Galileo played key roles in early sunspot observations, with Kepler using a camera obscura in 1607. The 1645-1715 period, known as the “Maunder Minimum,” was marked by a sharp decline in sunspot observations, raising questions about solar cycle transitions. The study used Kepler’s pre-telescopic drawings to better understand this unique event in astronomical history.
https://arstechnica.com/science/2024/07/how-keplers-400-year-old-sunspot-sketches-helped-solve-a-modern-mystery/