Hello all, I have seen an old calendar from 1793 which lists for every month sunrise and sunset times as well as day and night duration. For example, taking the month of April: sunrise at 5 h 20 m, sunset at 7 h 14 m; day length 13 h 20 min, night length 10 h 40 m.
Somebody asked me if it would be possible to establish the approximate geographical area for these predictions. I'm pretty sure it's not possible. Back then they used true solar time (or perhaps mean solar time?) so I guess these hours would have been valid for a whole parallel of latitude, with variations once you go north or south. Nevertheless, I made a simulation and realized that I cannot get close to these numbers. I don't know why. Perhaps because back then sunrise and sunset was not counted by solar limb, but by geometric center of the Sun? How did they do it? Regards, -- Dan-George Uza
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