notebook "Density of stars on the surface of the sky"

• https://laurentperrinet.github.io/sciblog/posts/2021-03-27-density-of-stars-on-the-surface-of-the-sky.html#Olber's-paradox
• https://astronomy.stackexchange.com/questions/43147/density-of-stars-on-celestial-sphere/43668#43668