My understanding is that at Columbus time they did not measured sun / moon positions, but instead based their predictions on the eclipse cycles - if you have lo

My understanding is that at Columbus time they did not measured sun / moon positions, but instead based their predictions on the eclipse cycles - if you have long enough record of past eclipses, you can notice that they are not random but the same timing sequence repeats after some time: https://en.wikipedia.org/wiki/Eclipse_cycle https://en.wikipedia.org/wiki/Eclipse_cycle