1,295. The Great Difficulty in Deriving This Procedure

Hilchos Kiddush HaChodesh 11:2

Scholars of astronomy and math throughout history have differed greatly regarding calculations of when the moon would appear. The wisest scholars have erred in this matter. Certain ideas were hidden from them and there were many doubts. Some made numerous calculations but were unsuccessful in identifying a process to determine when the moon would appear. They metaphorically plunged into raging waters, only to return with no more than a shard of pottery to show for their efforts.

Hilchos Kiddush HaChodesh 11:3

Eventually, by investing a lot of determined effort into their investigations, some scholars did discover a method to determine when the moon would appear. There are also traditions about such things that were transmitted by the Sages, as well as proofs that are not written in any commonly-known books. Because of this, the Rambam decided that it was appropriate to share a method of calculating the moon’s appearance that will be usable to anyone who is motivated to undertake the task.