And just to add.
I don’t have the time to look things up now but I for some reason I think that Lakewood001 is confusing things a drop.
The Gemora in RH discusses many calculations of Rabban Gamliel regarding the positioning of the new moon.
Sure these were known.
I did not discuss calculation of the positioning of the New Moon.
I discussed the time difference that elapses between New Moons to the exact millisecond.
From what I have seen that fact was written in the Gemorah but not known to be accurate till the 1990’s