Astronomers urged to fight 'tooth and nail' to protect dark skies

Astronomers Identify Unknown Class of Water-Rich Asteroids

Amateur astronomers needed: help classify stars with Gaia's data

Rudolf Wolf and Alfred Wolfer were both astronomers interested in the Sun. Wolf only counted sunspots that were "black" and clearly visible while Wolfer insisted that you must count every spot that could be seen, leading to a change in mathematical models