TIL Zurich's historic Semper Observatory showcases around 300 measuring instruments, sundials, astrolabes, and the telescope that astronomer Rudolf Wolf used to count sunspots. Wolf was a pioneer in the topic of sunspot research

https://library.ethz.ch/en/news-and-courses/news/news-articles/2022/11/den-himmel-erforschen-ein-blick-in-rudolf-wolfs-sammlung.html

https://www.reddit.com/r/todayilearned/comments/153zeaj/til_zurichs_historic_semper_observatory_showcases/