How Amateur Astronomers Helped Israel Win the War of Independence

From How Amateur Astronomers Helped Israel Win the War of Independence:

Mordechai Gihon, 85, a professor, archaeologist and historian, was a former intelligence officer in the pre-state Haganah's astronomers unit - amateur astronomers who assisted in gathering intelligence about the Arab Legion's movements in and around Jerusalem. Gihon recalls that in the fall of 1947, David Zaichik, a botany professor and an amateur astronomer, "said that he could help us with his telescopes. We tried it and discovered that his telescopes permitted us to see deep into enemy territory, 100 times better than we had in the past." About 30 amateur astronomers from Jerusalem were enlisted by Gihon and Zaichik to observe enemy positions from hills, towers and tall buildings in the city. The astronomers, who worked in shifts throughout the day, provided daily close-ups of Arab Legion positions at a level of definition that permitted the identification of firing apertures and gun barrels pointed at Jewish forces. Zaichik's people attached cameras to the telescopes and produced detailed pictures for intelligence officers.