Today, I discovered the Association of Lunar and Planetary Observers, founded 1 March 1947 in Las Cruces, New Mexico. I had no idea that they exist, even though we lived in Las Cruces for two years, and I worked with one of the founders, Walter Haas. Today, I joined.
On 1 December 2020, lining up on Mars, I saw a pair of stars that looked like a binary. I noted the time and their approximate position. Eta Piscium was discovered by S. W. Burnham in 1878.
|"But Gershon, you can't call it Gershon's equation|
if everyone has known it for ages."
(Sidney Harris, What's So Funny About Science?)
It turns out that there is a Gershon's equation which "everyone" has known about for 700 years.
One year later , at the request of the bishop of Meaux, he wrote The Harmony of Numbers in which he considers a problem of Philippe de Vitry involving so-called harmonic numbers, which have the form (2^m) * (3^n). The problem was to characterize all pairs of harmonic numbers differing by 1. Gersonides proved that there are only four such pairs: (1,2), (2,3), (3,4) and (8,9). -- https://en.wikipedia.org/wiki/Gersonides